µITRON4.0 Specification
Ver. 4.00.00

ITRON Committee, TRON ASSOCIATIONSupervised by Ken Sakamura
Edited by Hiroaki Takada

Copyright (C) 1999, 2002 by TRON ASSOCIATION, JAPANµITRON4.0 Specification (Ver. 4.00.00)
The copyright of this specification document belongs to the ITRON Committee of the
TRON Association.
The ITRON Committee of the TRON Association grants the permission to copy thewhole or a part of this specification document and to redistribute it intact withoutcharge or with a distribution fee. However, when a part of this specification document
is redistributed, it must clearly state (1) that it is a part of the µITRON4.0 Specification
document, (2) which part it was taken, and (3) the method to obtain the whole specification document. See Section 6.1 for more information on the conditions for using thisspecification and this specification document.
Any questions regarding this specification and this specification document should bedirected to the following:
ITRON Committee, TRON Association
Katsuta Building 5F
3-39, Mita 1-chome, Minato-ku,
Tokyo 108-0073, JAPANTEL: +81-3-3454-3191
FAX: +81-3-3454-3224§ TRON is the abbreviation of “The Real-time Operating system Nucleus.”§ ITRON is the abbreviation of “Industrial TRON.”§ µITRON is the abbreviation of “Micro Industrial TRON.”§ BTRON is the abbreviation of “Business TRON.”§ CTRON is the abbreviation of “Central and Communication TRON.”§ TRON, ITRON, µITRON, BTRON, and CTRON do not refer to any specific product or products.

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A Word from the Project Leader
Fifteen years have passed since the ITRON Sub-Project started as a part of the TRON
Project: a real-time operating system specification for embedded equipment control.
During this time, there has been a high degree of technological innovation on microprocessors, and the range of applications the ITRON Specifications cover has broadened considerably. The range of applications includes industrial usage such as controlof robots and manufacturing equipment in factories, and consumer usage such as officeautomation (OA) and home appliances. The application range has even extended to
new areas such as new information and communication tools and advanced digital consumer appliances. There is no doubt that the technological advantages of the ITRON
Specifications such as real-time response, compactness to maximize usage of system
resources, and flexible adaptability in specification has greatly contributed to the steady
expansion of the ITRON Specifications adaptable applications. The open architecture
policy of the TRON Project has also contributed to achieve a high degree of actual useof the ITRON Specifications.
The µITRON4.0 Specification, which is based on the µITRON3.0 Specification, hasbeen developed to reorganize concepts and terms, to improve compatibility and conformance level, to increase productivity in software development, to allow reuse of
application software, and to achieve more portability.
The increasing cases where communication and GUI focusing on modern network
applications, internet and intranet equipments, and debugging related middleware areused on the ITRON-Specification operating system serves as the background of theµITRON4.0 Specification. This trend created a demand for more rigorous compatibility and higher conformance level. The ITRON Specifications are designed on a concept called loose standardization and level for allowing applicability to low-end CPUs
with relatively scarce resources. However, strict standardization is required for software portability purposes. The specification satisfying these two contradictorydemands is the µITRON4.0 Specification. The µITRON4.0 Specification maintains theloose standardization, but develops the level concept to introduce a new property called
the Standard Profile. The Standard Profile supports strict standardization to facilitate
software portability. Profiles other than the Standard Profile is allowed to increase
compatibility in each application field.
The terms and concepts in the specification have been reorganized, defined, andexplained in more details, reducing as much implementation-dependent portion as possible in an effort to achieve completeness of the specification.
The µITRON4.0 Specification reflects the rich experience on the ITRON Specifications
and meets the actual users’ demands for new applications. Introduction and effective
utilization of the µITRON4.0 Specification in many fields including newly createdfields and applications is expected.

iµITRON4.0 Specification

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June, 1999
Ken Sakamura
Project Leader, TRON Projectii

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Preface
Fifteen years have elapsed since the ITRON Project started in 1984. By the efforts of
those involved, the µITRON Specifications have developed into de-facto standards forthe real-time kernel for embedded systems. Based on this achievement, sometimearound 1996 the ITRON Project started working towards a second phase of standardization to expand the specification from real-time kernel to related specifications suchas software components.
The µITRON4.0 Specification is the result of two years of intensive effort by both the
Kernel Specification WG of the Hard Real-Time Support Study Group (from April
1997 to March 1998) and its successor, the Kernel Specification WG of theµITRON4.0 Specification Study Group (from April 1998 to June 1999). The specification study held by both WGs was proceeded with monthly meetings and discussions
through email. Eventually, more than 1,000 emails regarding the discussion of thespecification were exchanged. Other standardization activities in the ITRON Project,
especially those done by the RTOS Automotive Application Technical Committee andthe Device Driver Design Guideline WG of the µITRON4.0 Specification Study
Group, produced an important part of the µITRON4.0 Specification.
During the second phase of the standardization, a new approach was adopted by the
ITRON Project. The ITRON Project opened the discussion of the µITRON4.0 Specification. In other words, anyone could participate in the discussion regardless of qualification. This approach was a major factor in enabling many engineers to participate in
the project. Prior to this, most of the engineers did not formerly participate in the discussion. The participation of application engineers as well as the participation of kernel engineers was very significant in organizing the specification.
Another new attempt of the µITRON4.0 Specification is defining the Standard Profile
in order to insure the portability of the software. Under conventional loose standardization policy, there is no enforced implementation agreement among members. Compromises are adopted, and it is up to the implementors to choose specificimplementation options. However, when defining the Standard Profile specification,
standardizing each and every feature of the µITRON Specifications was necessary andthis caused many disagreements among the members. Most disagreements were basedon the difference between application requirements rather than on the difference
between company interests. Nevertheless, members shared a common vision to create
a better specification.
Through the process outlined above, the µITRON4.0 Specification was completed
reflecting variety of ideas from a variety of point of views. I am personally proud of
the level of accomplishment of the µITRON4.0 Specification. I believe that this levelof accomplishment could not have been achieved by a single man or company.
To the readers of the µITRON4.0 Specification, I would like to remark that in the inter-iii

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ests of adhering to strictness in the specification, some readability was sacrificed. The
previous µITRON Specifications included tutorial-like contents for engineers who are
unfamiliar with a real-time operating system. On the other hand, the µITRON4.0
Specification is written seeking strictness rather than easiness in reading in order tosecure software portability. Hence, a criticism on a lesser understandability than theprevious specifications is considered to be unavoidable. Therefore we would like towork on some complementary documents such as a reference or a guide book for thisspecification. However, the editor’s responsibility still spans to statements which are
unnecessarily difficult to understand.
As a roadmap for the ITRON Specifications, the µITRON4.0 Specification Study
Group is working on the standardization of the debugging interface and creating guidelines for device driver designs. The creation of a certification system for theµITRON4.0 Standard Profile is also under consideration in the near future. We are surethat these activities will increase the acceptance of the ITRON Specifications as
de-facto real-time operating system standards.
Finally, I would like to express my gratitude to those who contributed to the standardization of the µITRON4.0 Specification. This includes those who participated in the
Kernel Specification WG of the µITRON4.0 Specification Study Group, those involvedin the ITRON Project, and those who directly or indirectly supported the process todevelop the µITRON4.0 Specification. I would also appreciate your continuous support for the standardization activities of the ITRON Project.
June 1999
Hiroaki Takada
Secretary of the the µITRON4.0 Spefication Study Group
Department of Information and Computer Sciences,
Toyohashi University of Technologyiv

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Organization of the Specification Document
This document is the specification of the µITRON4.0 (or the µITRON4.0 Real-Time
Kernel) C-Language API Specification. The version number of specification is printed
on the cover and the top-right of each page.
The organization of this document is as follows.
In Chapter 1, a summary of the TRON Project and the ITRON Project and a design policy of ITRON Specifications are introduced. The position of the µITRON4.0 Specification is also described. This chapter describes the background information of theµITRON4.0 Specification and is not the main body of the µITRON4.0 Specification.
In Chapter 2, the common rule of the µITRON4.0 Specification and the software components that are standardized to be consistent with the µITRON4.0 Specification is
described. In Chapter 3, the various concepts and the common definitions for various
features of the µITRON4.0 Specification are shown. In Chapter 4, each feature of theµITRON4.0 Specification is described. In Chapter 5, the additional specifications aredescribed.
In Chapter 6, the reference information, such as the maintenance of specification andreference documents, is described. In Chapter 7, the lists and other information that
may be helpful in reading this specification is shown. These lists are the contents ofChapter 2 to Chapter 5, as seen from a different point of view. Chapter 6 and Chapter 7
are not the main body of the µITRON4.0 Specification.

v

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Description Format of the Specification Document
The following description format is used in this specification document.
[Standard Profile]
The specifications of the Standard Profile of the µITRON4.0 Specification are
described here. The scope of functionalities that the Standard Profile requires support,
the rule that is not applied to the Standard Profile but is included in the functionaldescriptions of the services calls and static APIs which the Standard Profile requires tosupport, and the rule that is not described in the µITRON4.0 Specification but applied
to the Standard Profile are described here.
[Supplemental Information]
Supplemental explanations of items difficult to understand to avoid misunderstanding
are described here. This is not the main body of the µITRON4.0 Specification.
[Differences from the µITRON3.0 Specification]
The differences of the µITRON4.0 Specification from the µITRON3.0 Specificationand their reasons are described here. The major differences and modifications from theµITRON3.0 Specification is mainly described, but not the additions or clarification
made in the µITRON4.0 Specification. This is not the main body of the µITRON4.0
Specification.
[Rationale]
The reasons for the specification decision are described here, when further explanations are necessary. This is not the main body of the µITRON4.0 Specification.
The functional descriptions of service calls and static APIs in Chapter 4 uses the format
described below.
The description of each service call or static API is started with the following header.

API Name

API Description

Profile“API Name” is a service call or a static API name. “API description” is a simple statement about the functionality of this service call or static API. If [S] is placed at the“Profile” field, the Standard Profile requires support for the service call or static API.
[Static API]This shows the description format of a static API in the system configuration file.
[C Language API]This shows the invocation format of a service call from the C Language.

vi

µITRON4.0 Specification

Ver. 4.00.00[Parameter]This lists all of the parameters for this service call or static API. It also includes a simple description, the data type, and the name of each parameter.
[Return Parameter]This lists all of the return parameters for this service call. It also includes a simple
description, the data type, and the name of each return parameter.
[Error Code]This lists all the main error codes that this service call returns. It also includes a simply
description of the cause of each error code. However, the main error codes that many
service calls may return due to the same cause are not described for each service call(see Section 2.1.6).
[Functional Description]
This describes the functionality of this service call or static API.
Italic characters within the names of service calls and constants represent other characters. For example, cre_yyy (yyy are italic characters) can be cre_tsk, cre_sem,
cre_flg, and so on.
For some parameters, such as object attributes or service call operational modes where
specific values are chosen, the following format is used:[x]x|yx || yx may or may not be specified
either x or y or both (bit-wise OR of x and y) may be specified
one of x and y must be specified

For example, ((TA_HLNG || TA_ASM) | [TA_ACT]) can take one of the following
four values.
TA_HLNG
TA_ASM(TA_HLNG | TA_ACT)(TA_ASM | TA_ACT)vii

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Table of Contents
A Word from the Project Leader .....................................................................................i
Preface .......................................................................................................................... iii
Organization of the Specification Document..................................................................v
Description Format of the Specification Document ......................................................vi
Table of Contents........................................................................................................ viii
Service Call Index ........................................................................................................xii
Static API Index...........................................................................................................xvi

Chapter 1 Background of µITRON4.0 Specification

1

1.1 TRON Project...................................................................................................1
1.1.1 What is the TRON Project?....................................................................1
1.1.2 Basic Sub-Projects .................................................................................3
1.1.3 Application Sub-Projects .......................................................................5
1.2 History and Current Status of the ITRON Specifications ................................6
1.2.1 Current State and Features of Embedded System..................................6
1.2.2 Requirements for RTOS on Embedded System.....................................7
1.2.3 Current Status of the ITRON Specifications..........................................9
1.3 ITRON Specification Design Policy ..............................................................11
1.4 Position of the µITRON4.0 Specification ......................................................121.4.1 Second Phase Standardization Activities of the ITRON Project .........121.4.2 Necessity of the µITRON4.0 Specification..........................................14
1.4.3 Introduction of the Standard Profile.....................................................15
1.4.4 Realization of a Wider Scalability .......................................................16
1.4.5 New Functions in the µITRON4.0 Specification .................................17

Chapter 2 ITRON General Concepts, Rule, and Guidelines

23

2.1 ITRON General Concepts ..............................................................................23
2.1.1 Terminologies ......................................................................................23
2.1.2 Elements of an API ..............................................................................24
2.1.3 Object ID Numbers and Object Numbers............................................26
2.1.4 Priorities...............................................................................................27
2.1.5 Function Codes ....................................................................................28
2.1.6 Return Values of Service Calls and Error Codes .................................28
2.1.7 Object Attributes and Extended Information .......................................30
2.1.8 Timeout and Non-Blocking .................................................................30
2.1.9 Relative Time and System Time ..........................................................32
2.1.10 System Configuration File ...................................................................32
2.1.11 Syntax and Parameters of Static APIs..................................................34
2.2 API Naming Convention ................................................................................36
2.2.1 Software Component Identifiers ..........................................................36
2.2.2 Service Calls ........................................................................................37
2.2.3 Callbacks..............................................................................................37
2.2.4 Static APIs............................................................................................37
2.2.5 Parameter and Return Parameter..........................................................39viii

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2.2.6 Data Types............................................................................................39
2.2.7 Constants ..............................................................................................40
2.2.8 Macros..................................................................................................41
2.2.9 Header Files .........................................................................................412.2.10 Kernel and Software Component Internal Identifiers...........................41
2.3 ITRON General Definitions............................................................................412.3.1 ITRON General Data Types .................................................................412.3.2 ITRON General Constants ...................................................................44
2.3.3 ITRON General Macros .......................................................................48
2.3.4 ITRON General Static APIs .................................................................48

Chapter 3 Concepts and Common Definitions in µITRON4.0

51

3.1 Glossary of Basic Terms .................................................................................51
3.2 Task States and Scheduling Rule....................................................................52
3.2.1 Task States............................................................................................52
3.2.2 Task Scheduling Rules .........................................................................55
3.3 Interrupt Process Model..................................................................................57
3.3.1 Interrupt Handlers and Interrupt Service Routines ..............................57
3.3.2 Ways to Designate an Interrupt ............................................................59
3.4 Exception Process Model ...............................................................................60
3.4.1 Exception Processing Framework ........................................................60
3.4.2 Operations within a CPU Exception Handler ......................................60
3.5 Context and System State ...............................................................................61
3.5.1 Processing Units and Their Contexts ...................................................61
3.5.2 Task Contexts and Non-Task Contexts.................................................62
3.5.3 Execution Precedence and Service Call Atomicity ..............................63
3.5.4 CPU Locked State ................................................................................64
3.5.5 Dispatching Disabled State ..................................................................66
3.5.6 Task State during Dispatch Pending State............................................67
3.6 Service Call Invocation from Non-Task Contexts ..........................................69
3.6.1 Service Calls that can be Invoked from Non-Task Contexts................69
3.6.2 Delayed Execution of Service Calls.....................................................70
3.6.3 Adding Service Calls that can be Invoked from Non-Task Contexts...71
3.7 System Initialization Procedure......................................................................72
3.8 Object Registration and Release.....................................................................73
3.9 Description Format for Processing Unit .........................................................74
3.10 Kernel Configuration Constants and Macros..................................................75
3.11 Kernel Common Definitions...........................................................................75
3.11.1 Kernel Common Constants ..................................................................75
3.11.2 Kernel Common Configuration Constants ...........................................77

Chapter 4 µITRON4.0 Functions
4.1
4.2
4.3
4.4

79

Task Management Functions ..........................................................................79
Task Dependent Synchronization Functions ................................................101
Task Exception Handling Functions.............................................................112
Synchronization and Communication Functions..........................................125
4.4.1 Semaphores ........................................................................................125ix

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4.4.2 Eventflags...........................................................................................134
4.4.3 Data Queues .......................................................................................145
4.4.4 Mailboxes..........................................................................................158
4.5 Extended Synchronization and Communication Functions .........................170
4.5.1 Mutexes..............................................................................................170
4.5.2 Message Buffers.................................................................................181
4.5.3 Rendezvous ........................................................................................193
4.6 Memory Pool Management Functions .........................................................214
4.6.1 Fixed-Sized Memory Pools................................................................214
4.6.2 Variable-Sized Memory Pools ...........................................................224
4.7 Time Management Functions .......................................................................235
4.7.1 System Time Management.................................................................235
4.7.2 Cyclic Handlers..................................................................................240
4.7.3 Alarm Handlers..................................................................................250
4.7.4 Overrun Handler ................................................................................258
4.8 System State Management Functions ..........................................................266
4.9 Interrupt Management Functions .................................................................279
4.10 Service Call Management Functions............................................................292
4.11 System Configuration Management Functions ............................................297

Chapter 5 Additional Specifications

305

5.1 The Specification Requirements for the µITRON4.0 Specification.............305
5.1.1 Basic Concept ....................................................................................305
5.1.2 Minimum Required Functionalities ...................................................306
5.1.3 Extension of the µITRON4.0 Specification .......................................307
5.2 Automotive Control Profile ..........................................................................308
5.2.1 Restricted Tasks .................................................................................308
5.2.2 Functionalities Included in the Automotive Control Profile ..............309
5.3 Version Number of the Specifications ..........................................................311
5.4 Maker Codes.................................................................................................312

Chapter 6 Appendix
6.1
6.2
6.3
6.4

315

Conditions for Using the Specification and the Specification Document ....315
Maintenance of the Specification and Related Information .........................316
Background and Development Process of the Specification........................318
Version History.............................................................................................322

Chapter 7 References
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9

323

Service Call List ...........................................................................................323
Static API List ..............................................................................................328
Static APIs and Service Calls in the Standard Profile ..................................329
Data Types ....................................................................................................331
Packet Formats .............................................................................................334
Constants and Macros ..................................................................................341
Kernel Configuration Constants and Macros ...............................................343
Error Code List.............................................................................................344
Function Code List .......................................................................................345x

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Index ...........................................................................................................................349xi

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Service Call Index
This is an index of the service calls defined in the µITRON4.0 Specification.
acp_poracre_alm
acre_cyc
acre_dtq
acre_flg
acre_isr
acre_mbf
acre_mbx
acre_mpf
acre_mpl
acre_mtx
acre_poracre_sem
acre_tsk
act_tsk
cal_por
cal_svc
can_act
can_wup
chg_ixxchg_pri
clr_flg
cre_alm
cre_cyccre_dtq
cre_flg
cre_isr
cre_mbf
cre_mbx
cre_mpf
cre_mplcre_mtx
cre_porcre_sem
cre_tsk
def_exc
def_inh
def_ovr
def_svc
def_texAccept Rendezvous..........................................................................203
Create Alarm Handler (ID Number Automatic Assignment)...........252
Create Cyclic Handler (ID Number Automatic Assignment) ..........243
Create Data Queue (ID Number Automatic Assignment)................148
Create Eventflag (ID Number Automatic Assignment) ...................136
Create Interrupt Service Routine......................................................284
Create Message Buffer (ID Number Automatic Assignment) .........184
Create Mailbox (ID Number Automatic Assignment) .....................161
Create Fixed-Sized Memory Pool (ID Number Automatic Assignment) ....216
Create Variable-Sized Memory Pool (ID Number Automatic Assignment) 226
Create Mutex (ID Number Automatic Assignment) ........................174
Create Rendezvous Port (ID Number Automatic Assignment)........197
Create Semaphore (ID Number Automatic Assignment).................127
Create Task (ID Number Automatic Assignment) .............................83
Activate Task ......................................................................................87
Call Rendezvous...............................................................................200
Invoke Service Call ..........................................................................296
Cancel Task Activation Requests .......................................................88
Cancel Task Wakeup Requests.........................................................105
Change Interrupt Mask.....................................................................290
Change Task Priority..........................................................................94
Clear Eventflag.................................................................................141
Create Alarm Handler ......................................................................252
Create Cyclic Handler......................................................................243
Create Data Queue ...........................................................................148
Create Eventflag ...............................................................................136
Create Interrupt Service Routine......................................................284
Create Message Buffer.....................................................................184
Create Mailbox.................................................................................161
Create Fixed-Sized Memory Pool....................................................216
Create Variable-Sized Memory Pool................................................226
Create Mutex....................................................................................174
Create Rendezvous Port ...................................................................197
Create Semaphore ............................................................................127
Create Task.........................................................................................83
Define CPU Exception Handler .......................................................299
Define Interrupt Handler ..................................................................282
Define Overrun Handler...................................................................260
Define Extended Service Call ..........................................................294
Define Task Exception Handling Routine........................................117xii

µITRON4.0 Specification
del_alm
del_cycdel_dtq
del_flg
del_isrdel_mbf
del_mbx
del_mpf
del_mpldel_mtx
del_pordel_sem
del_tsk
dis_dspdis_int
dis_texdly_tsk
ena_dspena_int
ena_texexd_tsk
ext_tsk
frsm_tsk
fsnd_dtq
fwd_por
get_ixx
get_mpf
get_mplget_pri
get_tid
get_timiact_tsk
ifsnd_dtq
iget_tid
iloc_cpu
ipsnd_dtq
iras_tex
irel_wai
irot_rdq
iset_flg
isig_semisig_tim
iunl_cpu
iwup_tsk

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Delete Alarm Handler.......................................................................254
Delete Cyclic Handler ......................................................................246
Delete Data Queue ...........................................................................150
Delete Eventflag ...............................................................................138
Delete Interrupt Service Routine......................................................286
Delete Message Buffer .....................................................................186
Delete Mailbox .................................................................................164
Delete Fixed-Sized Memory Pool ....................................................218
Delete Variable-Sized Memory Pool ................................................228
Delete Mutex ....................................................................................176
Delete Rendezvous Port ...................................................................199
Delete Semaphore ............................................................................129
Delete Task .........................................................................................86
Disable Dispatching .........................................................................272
Disable Interrupt...............................................................................288
Disable Task Exceptions...................................................................121
Delay Task ........................................................................................111
Enable Dispatching ..........................................................................273
Enable Interrupt................................................................................289
Enable Task Exceptions....................................................................122
Terminate and Delete Invoking Task ..................................................91
Terminate Invoking Task ....................................................................90
Forcibly Resume Suspended Task....................................................109
Forced Send to Data Queue..............................................................153
Forward Rendezvous ........................................................................206
Reference Interrupt Mask.................................................................291
Acquire Fixed-Sized Memory Block ...............................................219
Acquire Variable-Sized Memory Block ...........................................229
Reference Task Priority ......................................................................96
Reference Task ID in the RUNNING State......................................269
Reference System Time....................................................................238
Activate Task ......................................................................................87
Forced Send to Data Queue..............................................................153
Reference Task ID in the RUNNING State......................................269
Lock the CPU ...................................................................................270
Send to Data Queue (Polling)...........................................................151
Raise Task Exception Handling........................................................119
Release Task from Waiting...............................................................106
Rotate Task Precedence....................................................................267
Set Eventflag.....................................................................................139
Release Semaphore Resource...........................................................130
Supply Time Tick .............................................................................239
Unlock the CPU ...............................................................................271
Wakeup Task.....................................................................................104xiii

µITRON4.0 Specification
loc_cpu
loc_mtx
pacp_porpget_mpf
pget_mpl
ploc_mtx
pol_flg
pol_sem
prcv_dtq
prcv_mbf
prcv_mbx
psnd_dtq
psnd_mbf
ras_texrcv_dtq
rcv_mbf
rcv_mbx
ref_alm
ref_cfg
ref_cyc
ref_dtq
ref_flg
ref_isr
ref_mbf
ref_mbx
ref_mpf
ref_mplref_ovr
ref_porref_rdv
ref_sem
ref_sys
ref_tex
ref_tsk
ref_tstref_ver
rel_mpf
rel_mplrel_wai
rot_rdq
rpl_rdv
rsm_tsk
set_flg
set_timVer. 4.00.00

Lock the CPU...................................................................................270
Lock Mutex ......................................................................................177
Accept Rendezvous (Polling)...........................................................203
Acquire Fixed-Sized Memory Block (Polling) ................................219
Acquire Variable-Sized Memory Block (Polling)............................229
Lock Mutex (Polling).......................................................................177
Wait for Eventflag (Polling) .............................................................142
Acquire Semaphore Resource (Polling)...........................................131
Receive from Data Queue (Polling) .................................................155
Receive from Message Buffer (Polling)...........................................189
Receive from Mailbox (Polling) ......................................................166
Send to Data Queue (Polling) ..........................................................151
Send to Message buffer (Polling).....................................................187
Raise Task Exception Handling .......................................................119
Receive from Data Queue ................................................................155
Receive from Message Buffer..........................................................189
Receive from Mailbox......................................................................166
Reference Alarm Handler State........................................................257
Reference Configuration Information ..............................................301
Reference Cyclic Handler State .......................................................249
Reference Data Queue State ............................................................157
Reference Eventflag Status ..............................................................144
Reference Interrupt Service Routine State.......................................287
Reference Message Buffer State ......................................................191
Reference Mailbox State..................................................................168
Reference Fixed-Sized Memory Pool State .....................................222
Reference Variable-Sized Memory Pool State .................................233
Reference Overrun Handler State ....................................................264
Reference Rendezvous Port State ....................................................212
Reference Rendezvous State ............................................................213
Reference Semaphore State .............................................................133
Reference System State....................................................................278
Reference Task Exception Handling State .......................................124
Reference Task State ..........................................................................97
Reference Task State (Simplified Version).......................................100
Reference Version Information ........................................................302
Release Fixed-Sized Memory Block................................................221
Release Variable-Sized Memory Block............................................231
Release Task from Waiting...............................................................106
Rotate Task Precedence....................................................................267
Terminate Rendezvous .....................................................................210
Resume Suspended Task ..................................................................109
Set Eventflag ....................................................................................139
Set System Time...............................................................................237xiv

µITRON4.0 Specification
sig_sem
slp_tsk
snd_dtq
snd_mbf
snd_mbx
sns_ctx
sns_dpnsns_dspsns_loc
sns_texsta_alm
sta_cyc
sta_ovr
sta_tsk
stp_alm
stp_cyc
stp_ovr
sus_tsktacp_portcal_por
ter_tsktget_mpf
tget_mpl
tloc_mtx
trcv_dtq
trcv_mbf
trcv_mbx
tslp_tsk
tsnd_dtq
tsnd_mbf
twai_flg
twai_sem
unl_cpu
unl_mtx
wai_flg
wai_sem
wup_tskVer. 4.00.00

Release Semaphore Resource...........................................................130
Put Task to Sleep ..............................................................................103
Send to Data Queue..........................................................................151
Send to Message buffer ....................................................................187
Send to Mailbox ...............................................................................165
Reference Contexts...........................................................................274
Reference Dispatch Pending State ...................................................277
Reference Dispatching State ............................................................276
Reference CPU State ........................................................................275
Reference Task Exception Handling State .......................................123
Start Alarm Handler Operation ........................................................255
Start Cyclic Handler Operation ........................................................247
Start Overrun Handler Operation .....................................................262
Activate Task (with a Start Code).......................................................89
Stop Alarm Handler Operation.........................................................256
Stop Cyclic Handler Operation ........................................................248
Stop Overrun Handler Operation .....................................................263
Suspend Task ....................................................................................108
Accept Rendezvous (with Timeout) .................................................203
Call Rendezvous (with Timeout)......................................................200
Terminate Task ...................................................................................92
Acquire Fixed-Sized Memory Block (with Timeout) ......................219
Acquire Variable-Sized Memory Block (with Timeout) ..................229
Lock Mutex (with Timeout) .............................................................177
Receive from Data Queue (with Timeout) .......................................155
Receive from Message Buffer (with Timeout) .................................189
Receive from Mailbox (with Timeout).............................................166
Put Task to Sleep (with Timeout) .....................................................103
Send to Data Queue (with Timeout).................................................151
Send to Message buffer (with Timeout) ...........................................187
Wait for Eventflag (with Timeout) ...................................................142
Acquire Semaphore Resource (with Timeout) .................................131
Unlock the CPU ...............................................................................271
Unlock Mutex...................................................................................179
Wait for Eventflag.............................................................................142
Acquire Semaphore Resource ..........................................................131
Wakeup Task.....................................................................................104xv

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Static API Index
This is an index of the static APIs defined in the µITRON4.0 Specification.
ATT_INI
ATT_ISR
CRE_ALM
CRE_CYC
CRE_DTQ
CRE_FLG
CRE_MBF
CRE_MBX
CRE_MPF
CRE_MPL
CRE_MTX
CRE_POR
CRE_SEM
CRE_TSKDEF_EXCDEF_INH
DEF_OVR
DEF_SVC
DEF_TEX

Attach Initialization Routine............................................................304
Attach Interrupt Service Routine .....................................................284
Create Alarm Handler ......................................................................252
Create Cyclic Handler......................................................................243
Create Data Queue ...........................................................................148
Create Eventflag ...............................................................................136
Create Message Buffer.....................................................................184
Create Mailbox.................................................................................161
Create Fixed-Sized Memory Pool....................................................216
Create Variable-Sized Memory Pool................................................226
Create Mutex....................................................................................174
Create Rendezvous Port ...................................................................197
Create Semaphore ............................................................................127
Create Task.........................................................................................83
Define CPU Exception Handler .......................................................299
Define Interrupt Handler ..................................................................282
Define Overrun Handler...................................................................260
Define Extended Service Call ..........................................................294
Define Task Exception Handling Routine........................................117xvi

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Chapter 1 Background of µITRON4.0
Specification
1.1 TRON Project1.1.1 What is the TRON Project?
TRON, which stands for “The Real-time Operating system Nucleus,” is a project
started by Dr. Sakamura of University of Tokyo in 1984 in an aim to establish an idealcomputer architecture. Through collaboration between industrial world and universities, the TRON Project is aiming to produce an entirely new concept computer architecture.
In an effort to reconstruct the computer architecture, the TRON Project envisions the
future to be a highly computerized society: a cyber society. In a cyber society, microcomputers are embedded in a majority of equipments, facilities, and tools that we
encounter in our daily life. These devices are connected through a computer networkand they work together in order to support our activities in various situations. Equipments with built-in computer and connected to the network are called “Intelligent
Objects” while the overall system where intelligent objects are connected and work
together is called “Highly Functional Distributed System” (HFDS). The realization of
the HFDS is the most important goal of the TRON Project.
The TRON Project, divided into basic sub-projects and application sub-projects, is currently in progress. In the basic sub-projects, research is being conducted on the computer system, a component of HFDS. Specifically, the following sub-projects are
currently in progress: ITRON (specifications of real-time OS for embedded systems
and the related specifications), BTRON (specifications of OS for personal computers
and workstations and the related specifications), CTRON (OS interface specification
for communication control and information processing), and TRON HMI (standard
guidelines for a human-machine interface of various products).
In the application sub-projects, analysis and evaluation are currently being conductedto solve problems associated with establishing a realistic application system in HFDS.
A simulation of the future computerized society is also conducted as a basis for evaluation of the architecture developed in the basic sub-projects. The application
sub-projects use the results of the basic sub-projects to solve the said problems while
the basic sub-projects, in turn, make use of the feedback coming from the application
sub-projects to further its research.

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Toward the 21st Century
The TRON Project aims to establish an ideal computer architecture based on the technology of the 21st century. Our goal is to implement a top of the von Neumann-typearchitecture using VLSI technology, while giving utmost importance to real-time operations and cost performance. We adapt a new integrated design approach to a wide
range of applications such as home electronics, industrial robots, personal computers,
work stations, main frames, and private branch exchange (PBX).
Open Architecture
The basic policy of the TRON Project is to make the results of its research available
through open specifications. Everyone can then freely develop and market his or her
own products based on these specifications. This policy is essential in achieving thegoal of developing HDFS. The TRON Association was established as the central organization to develop the TRON Specifications and to certify conformance to the specifications. Anyone can be a member of the TRON Association if they are in agreementwith the concept of TRON and operate within the rules of the TRON Association.
Loose Standardization
The TRON Specifications define the interface of a computer, not the hardware or software it is founded on. It also defines the interface of the OS, but not the OS itself. The
specifications are geared towards minimizing the development cost and upgrading the
educational effects on users and programmers by implementing program and data compatibility. Thus, the TRON Association adapts the loose standardization, where only
the design concept is defined. A developer can then freely implement a specific systemthat conforms to the design concept standard. Using a loose standard is a compromise
between implementing the compatibility between HFDS components and allowing forthe adaptation of new technologies.
The interface is defined in a layered structure, consisting of: the microprocessor
instruction set, OS kernel, OS outer kernel, data formats, communication interface
between objects, programmable interface, and the human-machine interface (HMI).
With the layered structure of the specifications, various developers can independently
implement different layers. Even in one system, different layers can be developed bydifferent companies, and under free competition, same layers can be developed by different companies.
Future Compatibility
In order to realize the upward compatibilities in the future, the TRON Project is notaffected by the compatibilities with the past. Many existing computer systems today
are an enhancement of their early architectures. In other words, they are like houses
renovated several times to make them larger. TRON, based on advanced VLSI technol2

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ogy, is an all-new architecture. TRON defines the standard data format, TAD (TRON
Application Databus) to ensure compatibility for data that are transmitted between
applications. The TAD format provides a means for TRON and other OS to coexist.
Standardization of Operation
Another goal of the TRON Project is to design computers anyone can operate, just likecars. Anyone can drive cars regardless of their manufacturer or model. The standardization of the HMI, just like in cars, is especially important for personal computers as it
makes further knowledge unnecessary when a change or a revision in hardware and/or
software components occur.

1.1.2 Basic Sub-Projects
ITRON (Industrial TRON) and JTRON
ITRON is an architecture for real-time operating systems (RTOS) for embedded systems. Details of the ITRON Specifications are provided in the following sections.
The JTRON Specification is a merger of the ITRON Specifications, which have beenaround for over 10 years, and the Java run-time environment, which excels in portability and network transparency. In application systems with the JTRON Specifications, it
is easy to develop programs that uses the strengths of both ITRON and Java. Moreconcretely, ITRON functions can be used to implement real-time control programs thathave severe timing constraints, while Java functions can be used to manage GUI andother network-related functionalities. The JTRON Specifications have the following
advantages. A real-time system with network functionalities can be constructed with
the ITRON Specifications and Java. Components that need performance tuning can becoded with the RTOS’s native code. On the other hand, components where portability
is significant can be coded with the Java language. Thus, these components can be
developed and debugged on a personal computer or a workstation.
The JTRON1.0 Specification was released in 1997, and the conforming products havealready been released. The JTRON2.0 Specification strengthens the communication
functionalities between the ITRON-Specification RTOS and the Java run-time environment.
BTRON (Business TRON)BTRON refers to the architecture of personal computers and workstations thatsmoothly exchange information between humans and machines. It is important toguarantee data compatibility using a uniform HMI and TRON Application Database(TAD).
The main feature of the BTRON HMI is the GUI that supports keyboards and electronic pens as input devices. A touch panel can also be used instead of an electronic3

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pen. BTRON is currently developing an HMI guideline that only supports pens.
TAD implements data compatibility between computers designed under the TRON
architecture. It is a generic data format that can handle documents, graphics, and otherreal-time data (e.g. audio and video) for various environments.
BTRON1, BTRON2, BTRON3, and µBTRON Specifications have been released tomeet our goals mentioned above. BTRON1 is designed to be implemented on a limited
hardware resource. On the other hand, BTRON2 and BTRON3 are designed to makefull use of the hardware resources of powerful computer systems. µBTRON is a
BTRON Specification for PDAs and it provides power management function.
The BTRON1-Specification OS, which runs on a notebook type computer, was firstreleased in 1991. TRON-Specification keyboards have also been developed for
BTRON-Specification computers. They are designed for easier use and are less fatiguing than previous keyboard models. Electronic digitized pens are also used as a pointing device because they are more capable for handwritten character inputs and picturedrawings compared to mice.
TRON-Specification keyboards were first sold in 1991. Now research is being conducted on the following areas: a new window system architecture for BTRON, TRON
Application Control Language (TACL) which implements batch processing of graphical applications under BTRON, multi-media TAD specification, and TRON code thathas a multi-language and multi-lingual support.
CTRON (Communication and Central TRON)CTRON is an operating system interface that can be commonly applied to every
exchange, communication, and information processing node on a communication network. Since the 1980s, which is said to be the start of the information society era, evaluation experiments have been conducted on CTRON interface specification, software
portability and real time features.
The first version of CTRON Interface Specification was released in 1988. Since then,various works have been done to enhance and decrease the size of the specification, andin 1993, it was published as the new edition of “Original CTRON Specification Series.”
The certification system of the CTRON-Specification OS was started in 1989, and up
to this date more than 20 products have been certified.
From 1990 to 1992, an experiment on software portability was thoroughly executed.
The objective of this experiment was to quantitatively evaluate the portability of the
products conforming to the CTRON Interface Specifications. As a result, software
portability was proven to be high, although some problems regarding software portability were also found. These problems have been reflected to the CTRON Specifications.
As mentioned above, CTRON was established as the basic software platform for communication networks in the 1990s. Now it is being considered as the core of communication networks essential to the multi-media generation of the 21st century.
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TRON HMIThe HFDS is intended to help humans cope with daily lives by having multiple intelligent objects work together to provide support for humans. The TRON Project needs a
uniform HMI in all HFDS environments. The purpose of this sub-project is to create
an HMI guideline for intelligent objects, such as personal computers, electronic products, and automotive components.
The TRON HMI Guidelines describe the physical interactive parts that can be handled
by users or used in applications such as buttons, switches, and handles. Enableware
specification, and multi-language specifications are also available for a wide range ofusers. Enableware specification is for handicapped users while multi-language specification is for users who want to be able to control the computer in their own language.
With an HMI made according to this guideline, a user can switch to other systems easily without worrying about system differences such as compatibility.
The result of this sub-project was presented as “TRON Human-Machine Interface
Specifications.” In 1992 and 1993, the sub-project held competitions on HMI design inorder to evaluate its usefulness.

1.1.3 Application Sub-Projects
Up to this date, experiments and research have been conducted on various application
sub-projects, with the results taken as feedbacks to the basic sub-projects. Examples ofapplication sub-projects are the TRON-Concept Intelligent House, the TRON-ConceptIntelligent Building, and the TRON-Based Autotraffic Information System. The following sections introduce the four most recent application sub-projects being conducted.
Computer Augmented Environment
The computer augmented environment refers to an environment where computers areembedded in every machine, and each machine, in turn, is connected to a network, thus
expanding the functionalities of the real environment. It is being studied by many
researchers throughout the world. The term HFDS discussed above actually refers to
the computer augmented environment, and its construction is the TRON Project’s final
objective.
In order to realize the computer augmented environment, we are currently developing a“Computer Augmented Environment Control Script” designed to handle the control
embedded devices from personal computers and servers.
Multi-Media Network Service Platform (MNP)
The rapid spread of the internet and intranet provides an opportunity for networked
multi-media services.
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Since 1994, much work has been done to adapt CTRON to multi-media network services. CTRON is focusing on the usage flexible resources and implementation ofreal-time control functions on a network and its peripherals (such as nodes and routersfor gateway functions, servers and multi-media terminals.) New OS interface rules
have been added and technical problems regarding control functions required by the
focus mentioned above are being continuously examined since 1994.
Digital Museum
The digital museum is a futuristic museum that uses digital technology in every operation phase, including exhibits and presentations. The digital museum is not a virtualexhibit on the web. Virtual exhibition, itself, is a part of a digital museum. The concept of the digital museum is to extend and strengthened the real space of a physicalmuseum using cyberspace tools, such as computers and the Internet, thereby overcoming the limitations imposed on a real museum and at the same time increasing its
appeal.
The digital museum is an example of an HFDS application. The required computer
technology in constructing the digital museum is actually BTRON’s goal. This factshows the exclusiveness of BTRON technology and at the same time indicates that thedirection of the hypermedia technology developed under BTRON sub-project is correct.
Distributed Software Platform for Information Home Electronics
The digitalization of home electronics and the use of home networking have rapidly
advanced in the recent years while software is needed to control information homeelectronics are getting more and more complex. On the other hand, much shorter time
for the development of devices are being imposed, thus heightening the need for software platforms to increase software development efficiency.
Middleware groups have been built to connect information home electronics to networks, using µITRON-Specification RTOS. The µITRON Specifications provide afoundation for efficient software development while ensuring the connectivity andoperability of embedded products.

1.2 History and Current Status of the ITRON
Specifications
1.2.1 Current State and Features of Embedded System
With the progress in microprocessor technology, the range of applications in whichembedded systems are practically used has significantly increased. During the earlydays, embedded systems were mainly limited to industrial applications such as produc6

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tion line control. Now, embedded systems are rapidly spreading to office electronics,
communication products, and most recently, to consumer products like automobiles,
audio/video systems, televisions, cellular phones, electronic instruments, games, laundry machines, air conditioners, and lighting systems. The term embedded system now
applies to most of the electronic products we encounter in our daily lives.
With the increased range of applications for embedded systems, the functions thatthese systems must perform become more complex. In addition, the recent trend
towards digitalization and the increase in number of software-implemented process onhighly functional microprocessors makes embedded systems more significant.
In general, small-scale embedded systems, usually consumer products, are produced inlarge quantities compared to large-scale embedded systems typically found in industrial products, making the cost per product comparatively cheaper. While decreasing
the development costs for large embedded systems is given importance, decreasing the
manufacturing costs of small-scale embedded systems is significant. In particular,
because of the tight competition on product development, attempts are made to shorten
the development time of consumer products. In addition, sold softwares are rarely
redesigned, which results in a very short life cycle for system development.
In most small-scale embedded systems, the core processor, ROM and RAM, general I/
O devices, and some other devices are all in a chip called MCU (Micro Controller Unit,
sometime called “one chip micro processor.”) Since the development cost of the final
product is to be kept as low as possible, hardware resources on a MCU, especially thememory, are very limited. This limitation becomes a problem when developing softwares on a MCU. The highly efficient MCU has various kinds of processors optimized
and designed for applications.
In small scale embedded systems, improving software productivity is important in handling largely scaled and highly complex softwares. It is also significant in reducing thesoftware development time. It is often to use a high-level language like C, and an
RTOS, like a µITRON-Specification RTOS.

1.2.2 Requirements for RTOS on Embedded System
To keep up with the progress of high performance microprocessors technology, it isvery important for embedded systems to be cost-effective, especially since they are
now widely applied to consumer products. Also the number of software engineers
working on RTOS is also increasing as embedded systems are being applied to more
and more areas, making their education a lot more significant.
In a survey conducted by the TRON association every year from 1996, the survey
shows the greatest problem encountered by most engineers using an RTOS in an
embedded system is regarding education and standardization. The survey shows that
there are very few engineers who can handle RTOS and that the specifications of different operating systems are so large that switching to another OS would take a lot of7

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work. The survey also shows that the OS size and resources are too large, and most of
its features and functions do not meet actual requirements, leading to problems inmatching an OS with an application.
The TRON Project, giving importance to education from aspect that standardization ofconcept and technical-term, has decided to provide a standardized RTOS specificationthat can easily be applied in many embedded systems.
The most difficult problem encountered in providing a standardized RTOS specification for embedded systems is finding the balance between providing the highest performance that the hardware allows and upgrading software development productivity. On
MCU based systems with tight limitations on hardware resources, reaching the maximum hardware performance will only be achieved by carefully selecting the appropriate RTOS. On the other hand, improving software development productivity involves
increasing the abstraction of OS services and guaranteeing software portability regardless of the hardware in use would increase the gap between OS services and the hardware architecture. This gap would cause significant overhead and getting a highperformance from hardware would be a lot more difficult.
The compromise between these two goals highly depends on the performance ofembedded products. Particularly, it is meaningless to lower the runtime performanceof small scale embedded systems just to keep the final product’s cost low and improve
its portability. On the contrary, since large scale systems are often recycled, portability
is a very important issue. The optimal solution to this problem is not well defined andthe optimal balance point changes with the progress of microprocessors.
Small and large scale embedded systems often require different RTOS features. Small
scale systems would often suffer decreased performance and increased program size
from using an RTOS with many high-level features that are really unnecessary. On theother hand, an OS with many high-level features is useful for large-scale embedded
systems, as it helps improve software development productivity.
As seen from above, the requirements for an RTOS differ depending on the scale andthe necessary features of each embedded system. It would be possible to define an
RTOS specification for each application scale or required feature sets. However, inconsidering the education of software engineers, the software circulation, and the support for development tools, defining a scalable OS specification that can adapt to theneeds of a variety of embedded systems, would be very useful.
The following is a summary of the requirements for the specification of an RTOS on
embedded systems:• To be able to get the maximum performance from the hardware.
• To be useful in increasing productivity for software.
• To be able to adapt to any system scale (scalability).
In addition to the above technical requirements, it is also important that the specification be open. Because embedded systems are involved in all the electronics products
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that we encounter daily, it is necessary not only to make the specification available toevery one, but also to make it royalty free so that anyone can implement and sell products based on the specification.

1.2.3 Current Status of the ITRON Specifications
The ITRON Project started in 1984, and it has developed and released a series of
ITRON Real-Time Kernel Specifications. The project gave utmost importance to thestandardization of kernel specifications because small scale systems often only use justthe kernel functions.
The first ITRON specification was developed in 1987 as the ITRON1 Specification.
Many real-time kernels were developed based on the ITRON1 Specification, and they
served to be useful in verifying the specification’s usability. Later, in 1989, the ITRON
Project released two specifications: the µITRON Specification (ver. 2.0) and the
ITRON2 Specification. The µITRON Specification is for small systems on an 8 or
16-bit MCUs. One of its characteristics is limited the kernel functionality. The
ITRON2 Specification, on the other hand, is designed for larger systems on 32-bit
MCUs. The µITRON Specifications have been implemented on many different MCUs
with limited memory and limited computational resources. It is also used on a wide
variety of embedded systems and it provides practical functionality without large memory requirements. In fact, µITRON-Specification kernels have been developed on mostmajor MCUs used in embedded systems.
In order to apply the µITRON Specifications to a wide range of fields, functionality andperformance are necessary. Even though the µITRON Specifications was not designed
for 32-bit processors, the µITRON-Specification kernel is now being implemented on
32-bit MCUs since the kernel does not consume significant memory. Because of this,the specification was revised to make it scalable on MCUs ranging from 8-bits to
32-bits. The revised edition was the µITRON3.0 Specification, released in 1993. TheµITRON3.0 Specification includes connection functions that allow a single embedded
system to be implemented over a network. IEEE CS Press published the English version of the µITRON3.0 Specification under the title “µITRON3.0: An Open and Porta ble Real-Time Operating System for Embedded Systems.”
At present, there are approximately 50 ITRON real-time kernel products for 35 processors registered to the TRON association. There is also a U. S. software vendor that hasdeveloped a µITRON-Specification kernel. Since the µITRON-Specification kernel issmall and is easy to implement, many users have developed their own versions forin-house use. There are also several implementations that besides products, and someversions of the µITRON kernel are distributed as free software.
The reason that µITRON kernels are used in so many instances is that it supports awide range of applications. Table 1-1 shows examples of some devices that use
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ifications are used often in consumer products and it has become the standard amongindustrial companies. Many companies develop their own ITRON-Specification kernel, which indicates that the ITRON Specifications are truly open standards.
Table 1-1. Major Fields where ITRON-Specification Kernels are Applied
Audio/Visual Equipment, Home ApplianceTVs, VCRs, digital cameras, STBs, audio components, microwave ovens, rice cookers, air-conditioners, washing machines
Personal Information Appliance, Entertainment/Education
PDAs (Personal Digital Assistants), personal organizers, car navigation systems, game gear, electronic musical instruments
PC Peripheral, Office Equipment
printers, scanners, disk drives, CD-ROM drives, copiers, FAX,
word processors
Communication Equipment
answer phones, ISDN telephones, cellular phones, PCS terminals,
ATM switches, broadcasting equipment, wireless systems, satellites
Transportation, Industrial Control, and Others
automobiles, plant control, industrial robots, elevators, vending
machines, medical equipment, data terminals

In addition to the real-time kernel specifications, the ITRON Project also provides the
ITRON/FILE Specification that provides file management features compatible with the
BTRON-Specification file system.
Many widely used products use processors with the ITRON Real-Time Kernel Specification. The µITRON-Specification kernel has been especially useful on MCUs, whichwere not previously used on RTOS due to memory and speed restrictions. TheµITRON Specification brings us closer to achieving the standard real-time kernel specification possible.
The object of standardization is now widened to include, not just the kernel, but also
software components, development tools, and related specifications. Also, researchand standardization on each application field is in progress (see Section 1.4.1). The
research and studies conducted by the TRON Project are all directed to realizing its
ultimate goal: the HFDS.

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1.3 ITRON Specification Design Policy
The following policies are adapted in designing the ITRON Specifications. These policies satisfy the requirements for an RTOS given in Section 1.2.2.
• Excessive hardware virtualization should be avoided in order to increase adaptability
to the hardware.
In order to maximize the performance of the hardware and thus, acquire highreal-time efficiency, excessive hardware virtualization should be avoided. The
phrase “adaptability to hardware” refers to improving the performance of the wholesystem by modifying the RTOS specifications and/or RTOS internal implementationaccording to the hardware’s performance and characteristics.
More specifically in the ITRON Specifications, items that should be standardized
regardless of the hardware structure are clearly divided from the items that can be
optimized according to the hardware’s performance and characteristics. Standardized items includes task-scheduling rules, system call names, system call functionalities, names, order, and meanings of system call parameters, and names andmeanings of error codes. On the other hand, items that would cause a decline in performance are not forcibly standardized, instead, standardization and virtualization
are purposely avoided. For instance, bit width of parameters and methods for invoking interrupt handlers are decided on each implementation.
• Adaptability to applications should be considered.
Adaptability to application refers to the approach to improve the over all system performance by modifying the kernel specifications and internal implementation methods in response to the kernel functionalities performance required by applications.
Since the object code for the OS is created for each application, adaptability toapplications approach works well in embedded systems.
The specification is designed in such a way that each kernel function is kept independent to each other as possible so that only the required function for each application are actually used. Providing a single functionality to each system call makes
incorporating of only the required functions easier. Most µITRON-specification
kernels are provided as libraries and only the required modules are extracted andlinked with application programs.
• Education of software engineers should be given importance.
Compatibility and portability are not of a great concern to softwares developed forsmall embedded systems because the software is not likely to be reused. However,standardizing the kernel specification is more important because it helps to educate
software engineers. It also make communications between software engineers easier because by unifying technical terms and concepts.
In the ITRON Specification, the education of software engineers is given impor-

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tance. By standardization, an engineer can widely apply what he learns once. The
usage of terms and naming of system calls, for example, are made as consistent as
possible. Educational text books for engineers are also in progress.
• A series of specifications should be developed and support levels should be definedin a specification.
In order for applications to adapt to various hardwares, a series of specifications thatallow different scalable levels of support are created. The series of real-time kernel
specifications made up to this date includes µITRON Specification (Ver. 2.0) for 8 to
16 bit MCUs and ITRON2 for 32 bit processors. With these specifications, the user
can scale each functionality as needed and include only those functionalities when
implementing the kernel. The µITRON3.0 specification separates the systems calls
into different levels of support to cover both small-scale and big-scale processors
within one specification.
Specifications for distributed systems over a network, and multi-processor systems
are also being considered for standardization under the ITRON Specification series.
• Various functionalities should be provided.
The ITRON Specifications provide a large set of primitives with different properties
to cover a wide range of functionality instead of limiting the number of primitives.
Using the primitives according to the natures and characteristics of the applicationand hardwares, improve performance during execution and makes program coding
easier.
The common concept among the above design policies is “loose standardization.”
Loose standardization means that some parts of the specification that would reduce thehardware performance are not forcibly standardized and are left to the developer toimplement on hardware and/or application. With loose standardization, maximum performance for various hardware platforms is achieved as shown in Figure 1-1.

1.4 Position of the µITRON4.0 Specification
1.4.1 Second Phase Standardization Activities of the ITRON
Project
As mentioned previously, the ITRON Project has been focusing on standardization ofreal-time kernel specifications. As the embedded systems become larger and more
complex, the need for standardization on the surrounding environments of the real-timekernel is increasing. In 1996, the ITRON Project started its second phase: expanding
standardization from kernel specification to the kernel’s related specifications, especially on software components for embedded systems.
In standardizing software components, not only the conditions for advancing the development and distribution of software components but also the interface for different
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Functions defined in the µITRON Specification
event
data
task
mailboxmanagement semaphore
flag
queue

others...

Adaptation to the processor architecture
Adaptation to application domains

AAA

AAAA

µITRON-Specification kernel adapted to Processor X
taskmanagement semaphore

data
queue

mailboxothersimplementationspecific

Adaptation to the application requirements

AAA AAA AAAAAAµITRON-Specification kernel adapted to Application A
task
mgmt.

semaphore

data
queue

impl.specificFigure 1-1. Adaptation according the µITRON Specifications
fields are being considered.
The following two issues are being discussed to prepare the conditions for advancing
the development and distribution of the components. The first problem is regarding the
distribution of software components. The difference in implementation amongµITRON kernels makes it difficult to ensure the distribution of software components.
To solve this problem, it is necessary to raise the level of kernel standardization while
keeping the advantages of loose standardization. The second problem is regarding the
support for software components with real-time capability. Many software components are required to have real-time capabilities and a framework is needed to allow thecoexistence of software components and application while satisfying software components’ real-time restrictions. The framework also allows multiple software components to be used together.
The discussion results regarding these two problems are reflected in the µITRON4.0
Specification. A standard method for designing embedded systems with real-time kernel is also proposed. A guideline for designing applications supporting software components with hard real-time capability is being created.
Standardization of software component interface in every field currently in progressincludes API (Application Program Interface) for TCP/IP protocol stacks and standard
interface for Java execution environments.
The TCP/IP protocol stack has taken an increasing significance in the field of embedded systems, recently. Though the socket interface is in wide use today as a TCP/IP
API, it is not appropriate for embedded systems (particularly small-scale ones) becauseof such problems as its large overhead and the necessity of dynamic memory manage-

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ment within the protocol stack. The ITRON TCP/IP API Specification, which is a standard TCP/IP API for embedded systems, has been designed to solve these problems of
the socket interface and to enable a compact and efficient implementation of the TCP/
IP protocol stack. The ITRON TCP/IP API Specification has been published on May,
1998.
Java technology is also drawing interest these days. A practical approach for applying
Java technology to embedded real-time systems is to implement the Java runtime environment on an ITRON-specification kernel. Then, build an application system
whereby the parts for which Java is best suited are implemented as Java programs, andthe parts taking advantage of the ITRON-specification kernel strengths are implemented as ITRON tasks. A key issue here is the standardization of the communicationinterface between Java programs and ITRON tasks. The JTRON2.0 Specification has
been designed to define this interface standard and published on Oct., 1998.
Besides software component support, defining the requirements for ITRON kernels
designed for automotive control and gathering proposals for the standard specification
were also conducted. The results are included in the µITRON4.0 Specification.
Works on standardizing interface between ITRON-Specification kernels and debugging
environments, and guidelines for designing device drivers are currently in progress.
Furthermore, C++ language bindings for the ITRON kernel are also being surveyed.

1.4.2 Necessity of the µITRON4.0 Specification
The need for reconsidering the real-time kernel specification arose during the ITRON
Project’s second phase mentioned in the last section and as a result, the µITRON4.0
Specification was created. This specification is considered as the 4th generation of
ITRON Specifications. The four main reasons why it was necessary to design theµITRON4.0 Specification is outlined below.
(a) To improve software portability
Embedded software continues to grow in complexity and size. The need for applications to easily switch to different kernels is increasing. Portability of softwares
developed on an ITRON kernel is also an important issue in the distribution of software components.
(b) To add functionality for supporting software components
The original µITRON Specifications left out some functionality to create software
components that are intended for the market. For example, the functionality to findthe context where a service routine of a software component is called was only
available on the extension level.
(c) To include new requirements and results of studies
From November 1996 to March 1998 a research group on hard real-time support
studied functionalities needed by a real-time kernel to make it easier to build a hard
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real-time system. The RTOS automotive application technique committee, from
June 1997 to March 1998, sorted out the requirements for real time kernels on automotive control applications. The results of these new requirements and studies
must be included in real time kernel specification.
(d) To include enhancements allowed by improved semi-conductor technology
Six years after the release of the µITRON3.0 Specification, the semi-conductor
technology has dramatically progressed and so is the performance of embedded
processors. The available memory size on processors has also drastically increased.
Some useful kernel functions that were left pending on the release of theµITRON3.0 Specification due to their overhead, can now be implemented with thecurrent technology.

1.4.3 Introduction of the Standard Profile
In order to improve software portability, the set of functions required for implementation and the functional specification of each service call should be strictly regulated. In
other words, the grade of specification standardization must be made stronger.
The standardization of µITRON Specifications has been done along the “loose standardization” policy which gives more importance to adaptability on hardwares and processors rather than software portability by reducing overheads and memory size duringexecution time. “Loose standardization” policy has made µITRON Specifications scalable and acceptable across a wide range of processors ranging from 8bits to 64bits.
This is one of the important reasons why the µITRON Specifications are widely
accepted. However, improving software portability and realizing scalability have many
contradicting aspects. It is difficult to realize both requirements at the same timewithin one specification.
To address the issue of portability while maintaining the “loose standardization” policy,
the µITRON4.0 Specification strictly defines the set of standard functions and their
specifications. This set of standard functions is called the “Standard Profile.” Alarge-scale system was assumed when defining the Standard Profile for the µITRON4.0
Kernel Specification. This is because larger systems require a more portable software.
Defining the Standard Profile leads to encouraging the building of softwares using only
functions provided by the Standard Profile, in cases where the portability of software
components is significant. It also leads to encouraging the implementation of kernels,
where the portability of software components are important, based on the Standard
Profile.
Within the Standard Profile, the specification is made to maximize software portability
while maintaining scalability. As an example, a mechanism for improving the portability of interrupt handlers while keeping overheads small, has been introduced. PreviousµITRON Specifications did not provide a way to maintain portability in prohibiting the15

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nesting of higher priority interrupts from within an interrupt handler. However, theµITRON4.0 Specification does.
In realizing scalability, service calls are made as independent to each other as possible,
and many sets of functions are made available, but only the necessary functions are
actually linked using the library link mechanism. This method is the same as that ofprevious µITRON Specifications. When it is difficult to link only the necessary functions using the library link mechanism, then the kernel is supposed to provide, only thenecessary primitives required to support more complex functions. This enables the
support of complex function without modifying the kernel, while minimizing the overhead in an application requiring no complex functions.
The Standard Profile assumes the following system image.
• The Standard Profile assumes the following system image.
• High-end 16 or 32-bit processor is used.
• The kernel code size is about 10 to 20KB when all functions are included.
• The whole system is linked into one module.
• The kernel object is statically generated.
Since the whole system is linked into a single module, service calls are invoked using
subroutine calls. The system does not have any particular protection mechanism.
The functions to be supported in Standard Profile includes all the level S functions(with modifications and expansions in some functions) and a part of level E functions(such as service calls with timeout, fixed-sized memory pool, cyclic handlers withspecification sorted out) of the µITRON3.0 Specification, and newly introduced functions (task exception handling, data queues, system state reference function, and soon). The static API used to state object creation information (to be described later) is
also supported.

1.4.4 Realization of a Wider Scalability
As described in the previous sections, the µITRON4.0 Specification maintains a policyof “loose standardization” and at the same time aims to provide a wider scalability thanthe previous ones.
It defines a minimum function set that can be made more compact than the previousµITRON Specifications and more adaptable to small systems. Specifically the waiting
state that was mandatory in the µITRON3.0 is no longer required. It is, however,replaced by the dormant state, which is mandatory. A kernel without the waiting state
allows tasks to operate within the same stack space. This reduces required memoryarea and overhead on context switches.
In order to support the requirements over the Standard Profile, the full set ofµITRON4.0 Specification provides more functions than the full set of the previous
specifications. Specifically it includes almost all the functions of the µITRON3.0
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Specification excluding the connection functions. Newly introduced functions inµITRON4.0 Specification includes: the new functions in the Standard Profile (task
exception handling, data queue, system state reference function), object creation functions for automatic assignment of ID number, interrupt service routine functions
enabling interrupt handling written while keeping portability, mutex to support priority
inheritance/ceiling protocols, overrun handler to detect the time left assigned to a task.
The full set of µITRON4.0 Specification is no less than the full set of ITRON2 Specification in terms of functionality.
In addition to the Standard Profile, an “Automotive Control Profile” is also defined.
The Automotive Control Profile targets automotive control applications. It is also considered as a function set that increases the software portability for systems smaller thanthose targeted by the Standard Profile. Specifically, Standard Profile functionalities,
such as functions with timeouts, suspended states, task exception handling, mail boxes,and fixed-sized memory pools are unnecessary and therefore was omitted. On theother hands, a task called a restricted task, is uniquely defined in the Automotive Control Profile. Restricted tasks do not enter the waiting state so restricted tasks with equal
priority can share the same stack area, reducing memory use. Unless there is no dependency on errors occurring from invoking a service call that enters the waiting state,
restricted tasks can be replaced by normal tasks, and the resulting behavior does notchange. The Automotive Control Profile is backward compatible with the Standard
Profile, even with the specific functionality of restricted tasks.
Figure 1-2 illustrates the µITRON4.0 supported function levels relative to theµITRON3.0 Specification. Compared to previous specifications, the µITRON4.0
Specification is more applicable to smaller and larger systems.

Full set
Level E
Standard
ProfileLevel S
Automotive
Control Profile
Level R
Minimum setµITRON3.0 Spec.

µITRON4.0 Spec.
Figure 1-2. Function Levels of µITRON4.0 Compared to µITRON3.0

1.4.5 New Functions in the µITRON4.0 Specification
New functions were added to the µITRON4.0 Specification are described below.
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Exception Handling Functions
The µITRON4.0 Specification defines the frame for exception handling, which was left
as implementation-dependent under the previous µITRON Specifications.
When the processor detects an exception condition, the processor starts a CPU exception handler. CPU exception handlers can be defined for each type of exception in theapplication. Since a CPU exception handler is global in the overall system, it is possible to check the context or the situation where an exception occurs, from within the
Task exception handling function is like a simplified version of a UNIX signal function
and is similar to the ITRON2 compulsion exception. The following is a list of typicalapplications using task exception handling functions:• Signal CPU exception, such as division by zero error, to a task.
• Send a task termination request to another task.
• Notify a task that the deadline has been reached.
Functionalities defined by the µITRON4.0 Specification for exception handling aredesigned so that they can be used as primitives in implementing more complicatedexception handlers.
Data Queues
A data queue is a mechanism to communicate with a single word data message. TheµITRON3.0 Specification permitted use of either a linked list or a ring buffer to implement a mailbox. However, in the µITRON4.0 Specification, the implementation of a
mailbox is limited to a linked list. In addition, a data queue, which is equivalent to a
mailbox implemented with a ring buffer, is introduced as a separate object.
Data queue feature was strongly required by the Automotive Control Profile and was atfirst, introduced as a unique feature of the Automotive Control Profile. However, sincedata queues are useful to other application areas and programs not requiring data
queues can be implemented without linking them to data queues, the date queue feature
was included in the Standard Profile.
System State Reference Functions
When creating software components assuming they are called by applications developed elsewhere, each service routine in each software component should work regardless of the context where it is called. However, in the µITRON3.0 Specification, only
the level E system call, ref_sys, was able to look at the present system state. Many
implementations do not support ref_sys, and even in cases where ref_sys is supported, the large overhead caused by reference to unnecessary information was a problem.
In response to this problem, 5 new service calls of the form sns_yyy have been introduced in the µITRON4.0 Specification. These service calls can refer the current state18

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of the system with small overheads. They can be invoked from any context and will
return a Boolean value (They will never return an error.) As an example, it is possible
to check, without worrying about overheads, whether a service call that enters waiting
state can be invoked or not.
Also, to handle processing that requires mutual exclusion, these service calls facilitate
the locking CPU (or disabling dispatch) temporarily, and then restore the system backto the original state after the processing is finished. The µITRON3.0 Specification has
no feature to restore the system to its original state once loc_cpu was invoked during
the dispatching disabled state. In the µITRON4.0 Specification, on the other hand, dispatching disabled state and CPU locked state are independent from each other so no
problems arise in locking the CPU.
Object Creation Functions for Automatic ID Number Assignment
In the µITRON3.0 Specification, the ID number must be provided in creating an object
dynamically. In large-scale systems, managing unused ID numbers is tedious. In theµITRON4.0 Specification, service calls are introduced to create an object using the ID
number assigned by the kernel instead of the ID number specified by the application.
The service calls return the assigned ID number.
Interrupt Service Routines
The interrupt handling architecture depends on processors and systems, and is a difficult part to standardize. The previous µITRON Specifications did not standardize thecoding of interrupt handlers and was determined and optimized for each processor andsystem. However in order to improve portability of device drivers, a method to write
portable device drivers is required.
The µITRON4.0 Specification introduced an interrupt service routine functions towrite interrupt handling while preserving the portability as well as the interrupt handler
functions in the previous specifications. The specification of interrupt service routine
is being designed with the goal of writing interrupt routines that depend only on interrupt generating devices.
MutexesPriority inheritance protocols and priority ceiling protocols are necessary to preventpriority inversions in a system with severe real-time constraints. Mutex is a mutual
exclusion mechanism that supports priority inheritance protocols and priority ceilingprotocols. It is a new feature of µITRON4.0 Specification. The mutex feature in thereal-time extension of POSIX real-time was referred to when designing the mutex forthe µITRON4.0 Specification.

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Overrun Handler
Overrun handler is another feature required in building a system with severe real-time
constraints. Overrun handler detects whether the amount of processing time assigned
to a task has been used up.
The simplest method to detect that a timing constraint has not been met in a system isby checking if the processing does not finish by the designated deadline. This can bedone using an alarm handler. However, this method do not prevent higher priority tasks
from continuing to run until its deadline, and as a chain reaction result, lower priority
tasks may not meet their deadlines. To solve this problem, a mechanism to detect whena task has used up given amount of time is required.
Standard Configuration Method
The Standard Profile assumes that the kernel objects, such as tasks and semaphores, arecreated statically. In order to port the application software written on a kernel conforming to the Standard Profile to another conforming kernel, in addition to the application program itself, object creation information must also be ported to the newkernel.
Previous µITRON Specifications did not standardize descriptions for the creation of
information in the kernel causing incompatibility in between kernels. For example,
one product may write the object information using C data structures, while anotherproduct may write the object information statically through a GUI configuration utility.
When porting a large scaled application to another kernel under such conditions, theamount of work on the porting of creation information can no longer be ignored.
Although the actual work of rewriting itself is not big, attention should be paid to thefact that the amount of time required to learn a different way of writing for different
products must be included in the total amount of work.
The µITRON4.0 Specification standardizes the coding of object creation informationand the way to configure the kernel or software components based on those information. The method of writing object creation information in the system configuration
file is called static API. The names of static APIs are the same as names of the service
calls with the corresponding function, but they are written in upper case letter. Static
APIs and service calls share the same parameters except that each element of a packet
is written within “{” and “}” instead of passing a pointer to the packet. Because of this,learning either the static API or the service call means learning the other. This isintended for educational purposes.
The configurator which processes static APIs must have a function to automaticallyassign ID number to the object with no ID number given. This allows omission of handling of automatic ID assignment, even when building an application with separately
developed modules and is very useful for large scale application development.
Static APIs for software components as well as static APIs for the kernel can be
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described in one system configuration file. This is another feature of the configuration
method of the µITRON4.0 Specification. By having the system configuration file processed by the software component configurator first, and then by the kernel configurator, complicated situations, such as the case where software components requiredifferent kernel objects on their configuration, can be handled.
In addition to the new features introduced above, the µITRON4.0 Specification also
reduces implementation-dependency by defining those items that were left ambiguousor implementation-dependent in each service call function under the µITRON3.0 Specification in order to improve the software portability. Also many improvements havebeen made over the µITRON3.0 Specification, such as sorting out terms and concepts,
sorting out data types of parameters, sorting out error codes, reassigning function codes
to service calls, standardizing constants and macros to retrieve kernel configuration,and standardizing system initialization process.

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Chapter 2 ITRON General Concepts,
Rule, and Guidelines
The ITRON general concepts, rules, and guidelines stated in this chapter are common
to the µITRON4.0 Specification and the software component specifications standardized to be consistent with µITRON4.0. These specifications are referred to as the
ITRON Specifications. In the ITRON general concepts, rules and guidelines, the “kernel specification” refers to the µITRON4.0 Specification and the “Standard Profile”
refers to the Standard Profile of the µITRON4.0 Specification.
[Supplemental Information]
As mentioned above, the concepts, rules, and guidelines in this chapter are applicable
to software component specifications as well. However, to make the µITRON4.0 Specification more understandable, we refer to certain areas specific to the µITRON4.0
Specification and its Standard Profile when necessary.

2.1 ITRON General Concepts
2.1.1 Terminologies
Terminologies used in this specification are defined below.
• Implementation-Defined: Items that are covered in the functional description of the
ITRON Specifications but are not standardized by the specifications. All implementation-defined items should be defined and described by the implementation’s documentation, such as the product manuals. The portability of any part of an application
program that depends on implementation-defined items is not guaranteed.
• Implementation-Dependent: Items covered in the functional description of the
ITRON Specifications, but whose behavior varies depending on the implementationand on the system operating conditions. The specifications do not guarantee thebehavior of an application program that relies on implementation-dependent items.
• Undefined: Situations with no guaranteed behavior. That is, a system failure mightoccur in any undefined situation. Items not mentioned in the specifications are generally undefined. There is no guarantee in the specification for the behavior of an
application program that generates an undefined situation.
• Implementation-Specific: Functionalities, which are beyond the scope of the ITRON
Specifications and are defined by the implementation.
[Supplemental Information]
Features defined by the implementation do not need to be internally consistent within
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the implementation and may vary according to the kernel or software component configurations. In the case where variations in feature definitions exists due to the kernelor software system configuration, implementation documents such as product manuals,
should describe the feature definitions for each configuration, as well the steps in configuring the kernel or the software component.

2.1.2 Elements of an API
An API (Application Program Interface) is a method used by an application program tointerface to the kernel or a software component. An API consists of the following elements:(A) Service Calls
The interface used by an application program to call a kernel or a software component
is referred to as a service call. The ITRON Specifications standardize the names andfunctions of service calls, as well as the types, orders, names, and data types of theirparameters and return parameters.
In a C language API, a service call is defined as a function call. However, it may be
implemented in other forms such as a preprocessor macro as long as it has the samefunctionality.
[Differences from the µITRON3.0 Specification]
In the µITRON3.0 Specification, the service call concept was referred to as a systemcall. The concept name has changed to service call in order to include software components as well as kernel functionalities. The term system call may still be used to referto a kernel service call.
(B) Callbacks
The interface used by a software component to call a routine registered by an application program is referred to as a callback. The registered routine is called a callback
routine. The ITRON Specifications standardize the names and functionality of callback routines, as well as the types, order, names, and data types of their parameters andreturn parameters.
The context in which a callback routine is executed is defined in each software component specification.
[Supplemental Information]
Callbacks are not used in the kernel specification.
(C) Static APIs
Static API refers to the interface used in both determining the kernel or software component configuration and defining the initial states of objects within a system configu-

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ration file. The ITRON Specifications standardize the names and functionalities ofstatic APIs as well as the types and order of their parameters.
Service calls, such as those used to register objects, may have a corresponding static
API. The functionality of a static API is equivalent to executing the corresponding service calls during system initialization, in the order listed in the system configuration
file. Some static APIs, like the ITRON general static APIs commonly used by kerneland software components, do not correspond to any service call at all.
(D) Parameters and Return Parameters
Parameters are data passed to service calls, callback routines, and static APIs. Returnparameters, on the other hand, are data returned by service calls or callback routines.
The ITRON Specifications standardize the names and data types of parameters andreturn parameters.
In a C language API, the return parameters, except the return value of a function, arereturned either through a pointer passed as an argument to a C language function, or asa data structure containing multiple parameters or return parameters. This type ofstructure is called a packet. The pointer that points to the area holding the returnparameters is not listed as a parameter. In the case where a pointer is pointing to a single return parameter, that pointer is not listed as a parameter, while a pointer to apacket, on the other hand, is listed as a parameter. In a C language API, an argument
pointing to an area holding a certain return parameter is named by prefixing the returnparameter’s name with “p_.” If the return parameter’s name starts with “pk_,” thepointer to the return parameter starts with “ppk_.” When parameters are too large topass as an argument, a pointer to the data area holding the parameter may be passed
instead. The naming convention for return parameters applies for parameters as well.
As a general rule, the data areas used to hold the parameters and return parameters of aservice call can be reused by the application once the service call returns. Also, data
areas used to hold callback routine parameters and return parameters for a software
component can be reused by the software component once the callback routine returns.
Exceptions to these rules are explicitly mentioned in the functional descriptions of service calls and callbacks.
[Rationale]
Standardizing the argument and return value names of functions is actually not necessary since they do not affect any kernel or software component API functionality.
However, the names of C language function arguments and function return values are
standardized in the ITRON Specifications because they are used frequently throughout
the specification and product manuals.
(E) Data Types
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return parameter data types. Some data type definitions are standardized in the ITRON
Specifications.
(F) Constants
The ITRON Specifications standardize the names, meanings, and values of the constants used as parameters, return parameters, and function codes for service calls. In a
C language API, constants are defined using preprocessor macros.
(G) Macros
A macro is an interface to convert values which are not bound to the system state without calling the kernel or software components. The ITRON Specifications standardize
the names and meanings of macros. In a C language API, macros are defined using
preprocessor macros.
(H) Header Files
There is one or more header files for each kernel and each software component containing declarations of service calls and definitions of data types, constants, and macros.
The ITRON Specifications standardize the names of these header files. If there are
more than one header file, the standardization also covers which header files containwhich declarations and definitions.
A header file containing the definitions of data types, constants, and macros specified
in the ITRON General Definitions section should be included in header files preparedfor each kernel and software component.
The configurator automatically assigning object ID numbers generates an automatic
assignment header file to contain the generated IDs. ITRON Specifications standardize
the names of these header files.
The header files standardized in the ITRON Specifications can be divided into morethan one file depending on the implementation. Care should be taken so that no error
arises even when the same header file is included multiple of times.
[Supplemental Information]
To prevent errors due to multiple inclusion of the same header file, define a specificheader identifier, for instance “KERNEL_H_,” as a preprocessor macro (“#define_KERNEL_H_”) at the top of the header file, and then enclose the whole header filewith “#ifndef _KERNEL_H_” and “#endif.”

2.1.3 Object ID Numbers and Object Numbers
The resources on which a kernel or a software component operates are generally
referred to as objects. Objects of each type are uniquely identified by numbers. In thecase where only a kernel or a software component API uses the object identifier and theapplication is allowed to freely assign numbers, the identifier numbers are called ID
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numbers. On the other hand, identifier numbers are called object numbers if they are
assigned according to an internal or external condition of the kernel or a software component.
Objects identified by ID numbers are registered to the kernel or a software component
when the application creates them. Objects identified with object numbers, however,cannot be created since their characteristics are determined by the internal and external
condition of the kernel or a software component. Registering these objects to the kernel or a software component is referred to as defining objects.
In general, positive serial numbers starting from 1 are used as object IDs. When theobjects are classified for protection mechanism reasons into user objects and systemobjects, increasing positive serial numbers starting from 1 are used for user object ID
numbers, and decreasing negative serial numbers starting from (–5) are used for systemobject ID numbers. In this case, only user objects are subject to automatic ID assignment. ID numbers from (–4) to 0 are reserved for special purposes.
[Standard Profile]
The Standard Profile does not require object classification nor does it require support
for negative ID numbers. At the very least, positive ID numbers from 1 to 255 must be
supported.
[Supplemental Information]
Interrupt handlers and rendezvous are examples of objects identified by object numbers. Object numbers are assigned to interrupt handlers according to hardware requirements while for rendezvous, object numbers are assigned based on the kernel’s internalrequirements. For these two types of objects, the application cannot freely assign numbers.

2.1.4 Priorities
Priorities are parameters determined by applications to control the processing order oftasks, messages, and so on. Positive serial numbers starting from 1 are used to represent priorities, where a smaller number indicates a higher precedence.
[Standard Profile]In the Standard Profile, the kernel must support at least 16 different levels of task priority (from 1 through 16). The number of message priority levels must be equal to or
greater than the number of task priority levels.
[Differences from the µITRON3.0 Specification]
The µITRON3.0 Specification allowed negative numbers to be used for system priorities; however, since negative values were seldom used, system priorities are limited topositive numbers in the µITRON4.0 Specification. Negative priorities are allowed but
they are implementation-specific. µITRON3.0 requires at least 8 priority levels (1–8).
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While the µITRON4.0 Specification does not specify the minimum number of priority
levels, the Standard Profile requires it to support at least 16 priority levels (1–16).

2.1.5 Function Codes
Function codes are numbers assigned to identify service calls. Invoking a service callfrom a software interrupt, for instance, makes use of a function code. However function codes are not necessary in invoking a service call from a subroutine.
In the ITRON Specifications, each service call of a kernel or a software component is
assigned a unique negative number as a function code. However, (–4) to 0 are reserved
for special purposes. Positive function codes represent extended service calls.

2.1.6 Return Values of Service Calls and Error Codes
In principle, the return value of a service call is a signed integer. If an error occurs during the execution of a service call, an error code with a negative value is returned. A
service call returns E_OK (= 0) or a positive integer if it completes its execution normally. Each service call specifies the meaning of its return value during normal completion. However service calls returning boolean values (BOOL type) and service
calls that never return are exceptions. A service call that never returns should be
declared as a function without a return value (i.e. a void type function) in a C languageAPI.
An error code is divided into two parts, the main error code represented by the lower 8
bits, and the sub error code represented by the remaining bits. Both the main error
code and the sub error code are negative, where the value of the sub error code is theresult of arithmetically shifting the error code to the right by 8 bits. The resulting combined error code is also negative. The names, meanings, and values of the main error
codes, defined under the ITRON General Definitions section, are common among thekernel and software components. Main error codes are classified into error classes,
according to the situations in which they occur and also according to the need for error
detection.
In the functional descriptions of service calls in the ITRON Specifications, only themain error codes returned by service calls are described, while sub error codes are
implementation-defined. Sub error codes are also specified in some software component specifications. Descriptions, such as “an E_XXXXX error is returned” or “an
E_XXXXX error occurs,” included within the functional descriptions of service calls
indicate that the service call returns an error code with a main error code of
E_XXXXX.
In principle, unless the main error code is classified as a warning class error, side
effects due to a service call that returns an error code do not arise. In other words, theinvocation of a service call does not change the system state. However, service calls
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with unavoidable side effects are exceptions to the above principle. Side effects due toa service call must be explicitly specified in the service call’s functional description.
The ITRON Specifications allows an implementation to omit detection of some errors
in order to reduce kernel overhead. In principle, the main error code’s class determines
if the error detection can be omitted. Each error class explicitly mentions if the detection of its errors can be omitted. Exceptions to this principle are explicitly described in
the service call’s functional description. In the case where an error that should havebeen detected but was not because the error detection was omitted, the resulting systembehavior is undefined.
The following main error codes occur in many, or almost all, of the service calls, thus
they are not described in every service call.
E_SYS
E_NOSPT
E_RSFN
E_CTX
E_MACV
E_OACVE_NOMEM

System error
Unsupported function
Reserved function code
Context error
Memory access violation
Object access violation
Insufficient memory

However, if these errors occur as a result unique to a service call, they are listed in theservice call’s description.
The error code returned by a service call that detects multiple errors is implementation-dependent.
[Supplemental Information]
The return value of E_OK (= 0) represents normal completion and is not an error code.
However, for convince reasons, there are cases where it is described as an error code
returned from a service call.
It is insufficient to simply examine the lower 8 bits of a return value for a negative number to determine whether the service call returned an error or not. This is because thelower 8 bits can be negative even when the service call completes normally and returns
a positive value.
[Differences from the µITRON3.0 Specification]
In the µITRON4.0 Specification, an error code now consists of two parts, the mainerror code and the sub error code. Main error codes are shared between the kernel andsoftware components. Sub error codes are intended to report the detailed cause oferrors, and to be used mainly for debugging purposes. For example, when the mainerror code is E_PAR (parameter error), the sub error code can be used to indicate
which parameter has an incorrect value. E_OK is not regarded as an error code.
Omitting error detection is explicitly permitted depending on the error class. Error
codes which are not listed in each service call have been revised.
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The µITRON3.0 Specification assumed the case where the return value of a service callis positive even though there were no service calls with a positive returned value. In
the µITRON4.0 Specification, however, kernel service calls with positive return values
exist. Also service calls that return boolean values have been introduced.

2.1.7 Object Attributes and Extended Information
Objects identified with ID numbers have object attributes while objects identified with
object numbers, on the other hand, may or may not have object attributes. Object
attributes that determine the operational mode and initial state of an object are definedwhen an object is registered. An object with an attribute value TA_XXXXX is called“an object with the TA_XXXXX attribute.” There is no interface available to read theobject attributes after the object is registered.
The values and meanings of available object attributes are defined in the functionaldescriptions of the service calls or static APIs that register the objects. TA_NULL(= 0) is used when there is no need to specify the object attribute.
A processing unit object may have extended information. The extended information is
specified at registration and is passed as a parameter when the object starts to execute.
Extended information does not have any effects on the operation of the kernel or a software component. There is no interface available to read the extended information froma specific object.
[Supplemental Information]
Examples of processing unit objects with extended information are tasks, interrupt service routines, and time event handlers such as cyclic handlers.
[Differences from the µITRON3.0 Specification]
In the µITRON3.0 Specification, objects identified with ID numbers must haveextended information, whereas in the µITRON4.0 Specification extended informationis only provided when necessary. Extended information is now passed as a parameter
when the object starts to execute and it cannot be read by object state reference service
calls.

2.1.8 Timeout and Non-Blocking
Timeout or non-blocking features, when necessary, can be made available to service
calls that might enter the WAITING state.
When a service call’s process is not completed within a specified time, the timeout feature cancels any further processing and returns from the service call immediately. In
this case, the service call returns an E_TMOUT error. Since there are no side effects
due to service calls returning an error, the system state, upon returning from thetimed-out service call remains unchanged. However, some service calls due to their30

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natures might prevent the system from proper restoration after the timeout cancellation.
These exceptional cases should be explicitly specified in the service call’s functionaldescription.
When the timeout duration of a service call is set to 0, the service call does not enter
the WAITING state even though it should. Setting the timeout duration of a service
call to 0 is called polling. Service calls that execute polling never enter the WAITING
state. The polling feature differs from the non-blocking feature described below in thatpolling cancels processing of the service call while non-blocking continues processing
the service call.
In the non-blocking feature, a service call that enters the WAITING state returns immediately with an E_WBLK error but the processing still continues. The application program is notified by some means when the process completes or when it is canceled.
Since the service call continues operating even after returning from its call, packets anddata areas used for parameters and return parameters should not be used for other purposes until the process completes.
Processing of a service call is referred to as “pending” when it is in the WAITING state
within the service call or when it continues operation due to a non-blocking service
call.
The functional descriptions of the service calls in the ITRON Specifications describes
the behavior when the service calls have no timeout, that is the behavior when the service calls wait forever. The description “entering the WAITING state” or “moved to
the WAITING state” in the functional descriptions of the service calls do not imply any
specific waiting duration. When a service call is invoked with a timeout duration, theservice call returns with E_TMOUT as the main error code when the duration expires.
In the case of polling, the service call does not enter the WAITING state and returns
immediately with E_TMOUT as the main error code. With the non-blocking feature,
the service call does not enter the WAITING state and returns E_WBLK as the mainerror code.
When specifying the timeout duration, TMO type, a positive value specifies the lengthof the timeout duration, TMO_POL (= 0) specifies polling, and TMO_FEVR (= –1)
specifies the timeout duration should be forever. TMO_NBLK (= –2) can also be
specified to indicate the non-blocking feature, depending on the service call. When thetimeout duration is specified, it must be guaranteed that the timeout action occurs afterat least the timeout duration has elapsed from the time the service call is invoked.
[Supplemental Information]
Kernel service calls do not have the non-blocking feature. Since a service call that executes polling never enters the WAITING state, the precedence of the invoking task
remains unchanged.
In typical implementations, if the timeout duration is set to 1, the timeout action will
occur at the second time tick after the service call is invoked. Since the timeout dura31

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tion cannot be set to 0 (because 0 is assigned to TMO_POL), the system never times
out on the first time tick after the service call is invoked.

2.1.9 Relative Time and System Time
Relative time of RELTIM type is used when specifying the time for an event to occur
with respect to a certain time such as the time when a service call is invoked. Whenrelative time is used, it must be guaranteed that the event occurs after at least the specified duration time elapsed.
Relative time can also be used to specify time-related actions other than event times,
such as time intervals between events, where the meaning of relative time is define foreach case.
System time of SYSTIM type is used when specifying absolute time. A function to set
the current system time is available in the kernel specification. Changing the systemtime using this kernel function will not change the time in the real world (called realtime) when an event specified using relative time is to occur. However, the system time
when an event occurs will change.
[Supplemental Information]
In typical implementations, if the relative time is set to 1, the event will take place on
the second time tick after the service call is invoked. If the relative time is set to 0, theevent will take place on the first time tick after the service call is invoked.

2.1.10 System Configuration File
A system configuration file defines the configuration of the kernel and software components as well as the initial state of objects. It can contain static APIs for the kernel andsoftware components, ITRON general static APIs (called general static APIs hereafter)
and also C language preprocessor directives. A tool that interprets static APIs in a system configuration file and configures the kernel or a software component is called aconfigurator.
The steps in processing a system configuration file is as follows (see Figure 2-1). The
system configuration file is first passed to the C language preprocessor. Then, it ispassed on to each of the software component configurators and then, finally to the kernel configurator.
The software component configurator interprets the static APIs pertaining to itself andother general static APIs included in the file passed from the C preprocessor or fromother previous configurators. The configurator then generates a source file, written in C
language, that is necessary for configuring and initializing the software component
itself. The software component configurator then adds static APIs for the next configurators when needed and removes the static APIs pertaining to itself to and from thepassed files, before passing it on to the next configurator.
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system.cfg

System configuration filewww_cfg.c

C laguage preprocessor

Configuration file forthe software component
Software component
configurator

www_id.hAutomatic assignment
header fileAAA

kernel_cfg.c

Configuration filefor the kernel

Kernel configurator

kernel_id.h

Automatic assignment
header fileFigure 2-1. Processing Procedure for a System Configuration FileThe kernel configurator interprets all static APIs included in the passed file and thengenerates a C language source file required for configuring and initializing the kernel.
If it detects statements that cannot be interpreted either as a static API for the kernel ora general static API, the kernel configurator reports an error.
Kernel and software component configurators ignore any lines starting with a “#” sign.
Software component configurators pass any lines starting with a “#” unchanged on to
the next configurator.
[Supplemental Information]
Static APIs added by a software component configurator for the next configurators
should not use preprocessor macros that are defined in the system configuration file andother files included through the preprocessor directive “#include.” The reason is thatthese preprocessor macros are already expanded after going through the C language
preprocessor.
[Rationale]
The steps in processing a system configuration file is standardized to effectively deal
with cases where the kernel and software components are developed independently.
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Passing the system configuration file first to the C language preprocessor makes the following things possible.
• It allows a system configuration file to be divided into multiple files through the useof the “#include” directive. For example, when embedding a software component
into a system, the necessary static APIs can be written in independent files. Thosefiles can then be included in the system configuration file.
• It allows macros to be used instead of raw integers to define object ID numbers andobject numbers.
• It allows conditional inclusion of configuration statements through the use of directives such as “#ifdef.” In turn, it makes the changing of kernel and software component configurations and the initial states of objects possible.
Configurators ignore lines starting with “#” because these lines usually pertain to
information generated by the preprocessor regarding the source file. However, configurators can still use these lines for informational purposes, such as generating error
messages.

2.1.11 Syntax and Parameters of Static APIs
The syntax of the static APIs is based on the syntax of the C language function call.
The parameters of a static API is based on the parameters of the corresponding service
call in the C language API. However, if a parameter is a pointer to a packet, the elements of the packet should be separated with a comma “,” and enclosed with braces “{”
and “}.”The static API parameters are classified into the following four classes, according toavailable expressions:(a) Integer Parameters with Automatic Assignment
A parameters of this class can be an integer (including a negative integer), an identifier, or a preprocessor macro (other than the restrictions mentioned below) which
expands to either an integer or an identifier. Example parameters of this class are
object ID numbers that are automatically assigned.
When a parameter of this class takes on the form of an identifier, the configurator
responsible for processing the static API containing that identifier assigns an integer
to that identifier. This assignment is called automatic ID number assignment by aconfigurator. The configurator generates a header file containing the macro definitions assigning integers to each identifier. Once the configurator assigns an integer
to an identifier, the identifier can be used in the same manner as a preprocessor
macro which expands to the assigned integer within static APIs that are processedby the configurator itself and by the following configurators.
(b) Integer Parameters without Automatic Assignment
A parameter of this class can only be an integer (including a negative integer) or a34

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preprocessor macro (other than the restrictions mentioned below) which expands toan integer. Example parameters of this class are object ID numbers that cannot be
automatically assigned and object numbers.
(c) Preprocessor Constant Expression Parameters
A parameter of this class is a constant expression that can be interpreted by a preprocessor. Only constants, macros, and operators that can be interpreted by a preprocessor can be used. Example parameters of this class are object attributes.
(d) General Constant Expression Parameters
A parameter of this class is any constant expression allowable in the C language.
Most parameters belong to this class.
Each static API defines the class of its parameters. Integer parameters with or without
automatic assignment and preprocessor constant expression parameters should be
explicitly mentioned in the functional descriptions of static APIs. Other parameters not
mentioned are assumed to be general constant expression parameters.
An ITRON general static API exists to include a file. Thus, there are two methods ofincluding a file in a system configuration file: using the preprocessor directive“#include” or using the general static API. The differences between these two methods are described below:• If preprocessor macros are used to define integer parameters with or without automatic assignment (hereafter, simply called integer parameters), only preprocessor
macros defined in the system configuration file or other files included through a preprocessor directive can be used.
• Files included using preprocessor directives can contain only static APIs and preprocessor directives. In contrast, files included using general static APIs can only contain preprocessor directives and declarations and definitions in the C language.
NULL, which is often used to indicate that the kernel must allocate a memory area, isrecognized as a symbol for static API parameters. A constant expression with a value 0
is not always interpreted as NULL. The behavior of such constant expression is implementation-dependent. Therefore, a NULL must not be macro-expanded by a preprocessor before a configurator processes it. In other words, NULL should not be defined
as a preprocessor macro in a system configuration file or other files included throughpreprocessor directives.
The configurator reports errors when it detects syntax errors or incorrect number ofparameters in static APIs. The method of handling errors found during the processingof static APIs is implementation-defined.
[Standard Profile]
In most static APIs, implementation-specific parameters can be added. In order forsuch implementations to conform to the Standard Profile, the configurator must correctly process the static APIs even when no implementation-specific parameters appear
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in the system configuration file. One of the methods to realize this is by supplying
default values for implementation-specific parameters.
[Supplemental Information]
Static APIs can be written in free format inside a system configuration file. There may
be white spaces, new lines and comments between words. The semicolon “; ” isrequired at the end of each static API statement.
Since C language enumerated constants and “sizeof” cannot be interpreted by a preprocessor, they cannot be used in preprocessor constant expression parameters.
Removing a NULL preprocessor macro definition from a file that is included into thesystem configuration file through a preprocessor directive is sometimes difficult
because of the file’s structure. This problem can be solved in the following way.
Define a specific identifier (for example, “CONFIGURATOR”) as a preprocessor
macro (“#define CONFIGURATOR”) at the top of the system configuration file.
Then, enclose the NULL preprocessor macro definition within “#ifndef CONFIGURATOR” and “#endif” directives.
[Rationale]
In order to simplify configurator implementations, static API parameters are classified
into four classes. A configurator must be able to determine object ID numbers andobject numbers properly so, excluding those that can be automatically assigned, object
ID numbers and object numbers are limited to those expanded to integers after preprocessing (integer value parameter). Some parameters, such as object attributes, may
have an effect on a registered object’s structure depending on its value. To be able touse conditional directives based on these parameters in a C source file generated by aconfigurator, only expressions whose values can be determined by the preprocessor areallowed (preprocessor constant expression parameters). For other parameters, any constant expression in the C language is allowed (general constant expression parameters).
If a configurator is implemented in this manner, it would not be able to determine allparameter values. Thus, its error checking capability is limited. Determining all theparameter values are possible by calling a compiler from the configurator and converting the constant expressions to values. However, since this approach requires modifying the configurator for each compiler, it has not been adopted as the standard method.

2.2 API Naming Convention
2.2.1 Software Component Identifiers
Software component identifiers are used to distinguish one set of standardized software
component APIs from another. The software component identifier is made up of two tofour characters. If a software component contains more than one functional unit, each36

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individual unit may have a software component identifier. Software component identifiers are defined in the software component specification.
Software components that define their own APIs are not subject to this convention.
However, to avoid naming conflicts with standardized software components, making
the software component identifiers 5 or more characters long, or prefixing the identifier
with “v” is recommended.
Hereafter, software component identifiers in lowercase are described as www, andthose in uppercase as WWW.

2.2.2 Service Calls
The standard form of a kernel service call name takes the form of xxx_yyy, where xxx
represents an operational procedure and yyy represents the target object of the operation. A service call derived from an xxx_yyy service call should be prefixed with theletter z resulting in a name of zxxx_yyy. If a service call is derived from a previously
derived service call zxxx_yyy, the name becomes zzxxx_yyy.
Names of service calls for software components take the form of www_xxx_yyy or
www_zxxx_yyy.
For naming implementation-specific service calls, the convention is to prefix “v”
before xxx or zxxx. This creates standard names of the form vxxx_yyy, vzxxx_yyy,
www_vxxx_yyy, or www_vzxxx_yyy. However, in the kernel specification, whena service call begins with an “i”, which indicates that the service call can be invokedfrom interrupt handlers, the service call’s name takes the form ivxxx_yyy instead of
vixxx_yyy.
[Supplemental Information]
Table 2-1 shows the abbreviations of the form xxx, yyy, and z used in the µITRON4.0
Specification and their English origin.

2.2.3 Callbacks
Since callback names are used as parameters, the naming convention for callbacks is
the same as that of parameters.

2.2.4 Static APIs
Generally, static APIs are named by capitalizing all the letters of the corresponding service call names. The names of static APIs that have no corresponding service call follow the naming convention of service calls, with the names still capitalized.
The names and meanings of ITRON general static APIs that are used both by the kerneland software components are specified in the ITRON General Definitions section.

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Table 2-1. Abbreviations used in the µITRON4.0 Specification and English originxxx
yyy
English origin
English origin
acp
acceptalm
alarm handler
act*
activate
cfg
configuration
att
attach
cpu
CPU
cal
call
ctx
context
cancancelcyc
cyclic handlerchgchangedpn
dispatch pending
clr
clear
dsp
dispatchcrecreatedtq
data queue
def
defineexc
exceptiondeldeleteflg
eventflagdisdisableinhinterrupt handler
dly
delay
ini
initializationena
enableint
interrupt
exd
exit and delete
isrinterrupt service routine
ext
exit
mbf
message buffer
fwd
forwardmbx
mail box
get
get
mpf
fixed-sized memory pool
loc*
lock
mpl
memory pool
pol
poll
mtx
mutex
ras
raise
ovr
overrun handler
rcv
receive
por
port
ref
refer
pri
priorityrelreleaserdq
ready queuerotrotaterdv
rendezvous
rpl
reply
sem
semaphorersm
resumesys
systemset
set
svc
service callsig
signaltex
task exception
slp
sleep
tid
task ID
snd
send
tim
time
sns
sense
tsk
task
sta
start
tst
task status
stp
stop
ver
versionsus
suspendterterminatezEnglish origin
unlunlocka
auto ID assign
wai*
wait
f
force
wup*
wake upiinterruptppollttimeout* Abbreviations with asterisks (*) are also used as a yyy abbreviation.
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2.2.5 Parameter and Return Parameter
The names of parameters and return parameters are all lowercase and are four to sevencharacters in length. The following conventions apply to parameter and return parameter names:
–id
–no
–atr
–stat
–mode
–pri
–sz
–cnt
–ptn
–tim
–cd

– ID (object ID number, ID type)– number (object number)– attribute (object attribute, ATR type)– state (object state, STAT type)– mode (service call operational mode, MODE type)– priority (priority, PRI type)– size (in bytes, SIZE type or UINT type)– count (in units, UINT type)– pattern– time– code

i–
max–
min–
left–

initial value of –maximum –minimum –quantity left of –p_–pointer to the memory area of a return parameter (or a parameter)pk_–
pointer to a packet
pk_cyyy
pointer to a packet passed to cre_yyy
pk_dyyy
pointer to a packet passed to def_yyy
pk_ryyy
pointer to a packet passed to ref_yyy
pk_www_cyyy
pointer to a packet passed to www_cre_yyy
pk_www_dyyy pointer to a packet passed to www_def_yyy
pk_www_ryyy
pointer to a packet passed to www_ref_yyy
ppk_–
pointer to the memory area of a pointer to a packet
If the names of the parameters and return parameters are identical, they are generally
the same data type.

2.2.6 Data Types
The names of data types are all uppercase and are two to ten characters in length. The
following conventions apply to data type names:–P
T_–
T_CYYY
T_RYYY

Pointer data type
Packet (data structure) type
Packet type passed to cre_yyy
Packet type passed to ref_yyy
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T_WWW_–
Data structure used by software components
T_WWW_CYYY
Packet type passed to www_cre_yyy
T_WWW_RYYY
Packet type passed to www_ref_yyy
The names and meanings of ITRON general data types that are used by both the kerneland software components are specified in the ITRON General Definitions section.

2.2.7 Constants
The names of constants are all uppercase and follow the convention described below.
(A) ITRON General Constants
The names of ITRON general constants that are used both by the kernel and software
components have no particular naming convention. The names and their respective
meanings and values are specified in the ITRON General Definitions section.
(B) Error Codes
Main error codes defined in the ITRON Specifications take the form E_XXXXX,
where XXXXX is approximately two to five characters in length. The form
EV_XXXXX is used for implementation-specific main error codes.
Sub error codes have no particular naming convention.
Error classes take the form EC_XXXXX, where XXXXX is approximately two to fivecharacters.
(C) Other Constants
Other constants take the form TUU_XXXXX or TUU_WWW_XXXXX, where UU isapproximately one to three characters in length, and XXXXX is approximately two toseven characters in length. Constants used for the same type of parameters or returnparameters should have the same identifier UU. TUU can be omitted for software component constants that are frequently used in many service calls and callbacks. In thiscase, such constants take the form WWW_XXXXX.
In addition to the above conventions, the following conventions apply to other constantnames:TA_–
Object attribute
TFN_–
Service call function code
TFN_XXX_YYY
Function code of xxx_yyy
TFN_WWW_XXX_YYY Function code of www_xxx_yyy
TSZ_–size of –TBIT_–
bit size of –TMAX_–
maximum –TMIN_–
minimum –40

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2.2.8 Macros
The names of macros are all uppercase and conform to the naming convention for constants. The names and meanings of ITRON general macros that are used by both thekernel and software components are specified in the ITRON General Definitions section.

2.2.9 Header FilesThe header file containing the definitions of data types, constants and macros, andother definitions specified in ITRON General Definitions section is named “itron.h.”
The header file containing all the service call declarations, data types, constants, andmacro definitions specified in the kernel specification are named “kernel.h.” Theautomatic assignment header file generated by the kernel configurator is named“kernel_id.h.”
Header files containing service call declarations and other definitions specified in asoftware component specification are generally named beginning with the software
component identifier. The automatic assignment header file generated by the software
component configurator is named in a similar manner. The names of these header files
are specified in the software component specification.

2.2.10 Kernel and Software Component Internal IdentifiersInternal identifiers are symbols registered to an object file’s symbol table for external
access. They are used within the kernel or a software component usually to refer toroutines and memory areas. Kernel and software component internal identifiers should
adhere to the naming convention defined below to avoid conflicts with other identifiersof an application program.
The names of kernel internal identifiers should begin with _kernel_ or _KERNEL_ at
the C language level. The names of software component internal identifiers should
begin with _www_ or _WWW_ at the C language level.

2.3 ITRON General Definitions
2.3.1 ITRON General Data Types
The ITRON general data types are as follows:B
H
W
D

Signed 8-bit integer
Signed 16-bit integer
Signed 32-bit integer
Signed 64-bit integer
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UB
UH
UW
UD

Unsigned 8-bit integer
Unsigned 16-bit integer
Unsigned 32-bit integer
Unsigned 64-bit integer

VB
VH
VW
VD

8-bit value with unknown data type16-bit value with unknown data type32-bit value with unknown data type64-bit value with unknown data type

VP
FP

Pointer to an unknown data type
Processing unit start address (pointer to a function)

INT
UINT

Signed integer for the processor
Unsigned integer for the processor

BOOL

Boolean value (TRUE or FALSE)

FN
ER
ID
ATR
STAT
MODE
PRI
SIZE

Function code (signed integer)
Error code (signed integer)
Object ID number (signed integer)
Object attribute (unsigned integer)
Object state (unsigned integer)
Service call operational mode (unsigned integer)
Priority (signed integer)
Memory area size (unsigned integer)

TMO

Timeout (signed integer, unit of time is implementation-defined)
Relative time (unsigned integer, unit of time is implementation-defined)
System time (unsigned integer, unit of time is implementation-defined)

RELTIM
SYSTIM
VP_INT

Pointer to an unknown data type, or a signed integer for theprocessor

ER_BOOL
ER_ID

Error code or a boolean value (signed integer)
Error code or an object ID number (signed integers and negative ID numbers cannot be represented)
Error code or an unsigned integer (the number of available
bits for an unsigned integer is one bit shorter than UINT)

ER_UINT

VB, VH, VW, VD, and VP_INT types are implementation-defined. Explicit type castis necessary during access or assignment of values to variables of these data types.
In the case where the number of bits needed to represent the system time exceeds thenumber of bits of an integer, SYSTIM can be defined as a data structure where the42µITRON4.0 Specification

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structure’s contents are implementation-defined.
[Standard Profile]In the Standard Profile, 64-bit integer data types (D, UD, and VD) included in the
ITRON general data types need not be supported.
In addition, the Standard Profile defines the minimum number of bits and the unit oftime of the ITRON general data types as follows:
INT
UINT

16 or more bits
16 or more bits

FN
ER
ID
ATR
STAT
MODE
PRI
SIZE

16 or more bits
8 or more bits
16 or more bits
8 or more bits
16 or more bits
8 or more bits
16 or more bits
equal to the number of bits in a pointerTMO
RELTIM
SYSTIM

16 or more bits, unit of time is 1 msec
16 or more bits, unit of time is 1 msec
16 or more bits, unit of time is 1 msec

[Supplemental Information]
SIZE is used to refer to the size of a large memory area, such as the stack size of a task
or an entire variable memory pool size. UINT is used to refer to the size of a smaller
memory area like a message length.
When SYSTIM is defined as a structure, variables of SYSTIM type cannot be manipulated by operators such as “+” and “–.” In order to maintain the portability of an
application program even in this case, operations on SYSTIM variables should be doneusing C language function calls and an operation module compatible with the definition of SYSTIM should be made available for each implementation.
[Differences from the µITRON3.0 Specification]CYCTIME, ALMTIME, and DLYTIME are replaced by RELTIM. SYSTIME has
been renamed to SYSTIM. STAT, MODE, and SIZE have been added. Complex
data types VP_INT, ER_BOOL, ER_ID, and ER_UINT have been added while
BOOL_ID has been removed. The size of a memory area is now handled using
unsigned integers.

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2.3.2 ITRON General Constants(1) General Constants
The ITRON general constants are as follows:
NULL

0Invalid pointer

TRUE
FALSE

1
0

True
False

E_OK

0

Normal completion[Differences from the µITRON3.0 Specification]
The invalid pointer has been changed from NADR (= –1) to NULL (= 0) for compatibility with the C language.
(2) Main Error Codes
There are ten classes of main error codes as defined below:(A) Internal Error Class (EC_SYS, from –5 to –8)
This class represents internal errors occurring inside the kernel or a software component. Omission of error detection of this class is implementation-defined.
E_SYS

–5

System error

This error code indicates an internal error of unknown cause occurred inside thekernel or a software component.
(B) Unsupported Error Class (EC_NOSPT, from –9 to –16)
This class represents errors due to functions that are either not specified in the ITRON
Specifications or are not supported by the implementation. Omission of error detectionof this class is implementation-defined.
E_NOSPT–9

Unsupported function

This error code indicates that the function is specified in the ITRON Specifications but is not supported by the implementation. This error is returned if a partof or all of the service call functionality is not supported. Errors falling under
E_RSFN and E_RSATR are not covered by this error code.
E_RSFN–10

Reserved function code

This error code indicates that a specified function code is not supported either in
the ITRON Specifications or by the implementation. This error occurs when aservice call is invoked from a software interrupt.
E_RSATR–11

Reserved attribute

This error code indicates that an attribute value is not supported either in the

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ITRON Specifications or by the implementation.
(C) Parameter Error Class (EC_PAR, from –17 to –24)
This class represents errors due to parameters assigned with incorrect values. Theseerrors can usually be detected statically. Omission of error detection of this class is
implementation-defined.
E_PAR

–17

Parameter error

This error code indicates that a parameter has an incorrect value that is usuallystatically detected. Errors falling under E_ID are not covered by this error
code.
E_ID

–18

Invalid ID numberThis error code indicates that an object ID number is invalid. This error only
occurs for objects identified by an ID numbers.
(D) Invoking Context Error Class (EC_CTX, from –25 to –32)
This class represents errors due to invocation of service calls from incorrect contexts.
Omission of error detection of this class is implementation-defined.
E_CTX

–25

Context error

This error code indicates that the context in which the service call is invoked isincorrect. Errors falling under E_MACV, E_OACV or E_ILUSE are not covered by this error code.
E_MACV–26

Memory access violation

This error code indicates that the specified memory area cannot be accessedfrom the context where the service call is invoked. This error is also returned if
the specified memory area does not exist.
E_OACV–27

Object access violation

This error code indicates that the specified object cannot be accessed from thecontext where the service call is invoked. When the objects are classified into
user objects and system objects, this error is returned if a system object isaccessed from a context where access to system objects is prohibited.
E_ILUSE–28

Illegal service call use

This error code indicates that the use of the service call is incorrect. Occurrenceof this error depends on the context from which the service call is invoked or on
the state of the target object.
(E) Insufficient Resource Error Class (EC_NOMEM, from –33 to –40)
This class represents errors due to insufficient resources needed to execute the service
call. Detection of errors of this class cannot be omitted.

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E_NOMEM–33

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Insufficient memory

This error code indicates that the service call failed to dynamically allocate
enough memory for a memory area.
E_NOID–34

No ID number available

This error code indicates that there is no ID number available for the target
object. This error is returned by the service call creating an object with an automatically assigned ID number.
(F) Object State Error Class (EC_OBJ, from –41 to –48)
This class represents errors due to the service call failing to execute because of the stateof the target object. Since the occurrence of these errors depends on the state of the target object, they do not necessarily occur every time the same service call is invoked.
Thus, dynamically checking for these errors is necessary. Error detection of this classcannot be omitted.
E_OBJ

–41

Object state error

This error code indicates that the service call cannot be executed due to the stateof the target object. Errors falling under E_NOEXS and E_QOVR are notcovered by this error code.
E_NOEXS–42

Non-existent object

This error code indicates that the service call is not able to access the target
object because the object does not exist. Since this error is returned only when
the specified object ID number is within a valid range, the object can be createdby specifying the same ID number that caused the error.
E_QOVR–43

Queue overflow

This error code indicates that the maximum queue limit or nesting level has
been exceeded.
(G) Waiting Released Error Class (EC_RLWAI, from –49 to –56)
This class represents errors due to a waiting task being released from the WAITING
state before its release condition is met. Detection of errors of this class cannot be
omitted.
E_RLWAI–49

Forced release from waiting

This error code indicates that the waiting task is forcibly released from waitingor that the waiting process is cancelled.
E_TMOUT–50

Polling failure or timeout

This error code indicates that the polling service call has failed or that the service call made with a timeout has expired.

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E_DLT

–51

Ver. 4.00.00
Waiting object deletedThis error code indicates that the object the task is waiting for has been deleted.
E_CLS

–52

Waiting object state changed

This error code indicates that the service call cannot be executed due to achange in the state of the object the service call is waiting for. When the statechange happened before the service call is invoked, the invoking task immediately returns with this error without moving into the WAITING state.
[Supplemental Information]
An example of the E_CLS error usage is in a service call that receives data through acommunication line. E_CLS can be used to indicate that the connection is abnormallydisconnected while the service call is waiting to receive data. The same error code canalso be used even when the abnormal disconnection occurred before the service call
was invoked.
(H) Warning Class (EC_WARN, from –57 to –64)
This class represents errors indicating that there are warnings associated with the service call’s execution. Errors in this class are exceptions to the general rule stating that
there are no side effects on the system state when a service call returns an error. Thatis, execution of service calls returning errors of this class can cause side effects on thesystem state. Detection of errors of this class cannot be omitted.
E_WBLK–57

Non-blocking call acceptedThis error code indicates that the non-blocking service call is currently being
executed.
E_BOVR–58

Buffer overflow

This error code indicates that a part of the received data was discarded due tobuffer overflow.
(I) Reserved Error Codes (from –5 to –96 except those defined above)
These main error codes are reserved for future versions of the ITRON Specifications.
(J) Implementation-Specific Error Codes (from –97 to –128)
These main error codes are used for implementation-specific errors. The names ofthese main error codes must be of the form EV_XXXXX.
[Differences from the µITRON3.0 Specification]
Main error codes E_ILUSE and E_NOID have been added for new functionalities of
the kernel specification, and E_CLS, E_WBLK, and E_BOVR have been added forsoftware component specifications. Connection function errors of the form
EN_XXXXX, and E_INOSPT, which were exclusive to ITRON/FILE Specification,
have been removed. Some of the main error codes were reclassified and their values
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reassigned. Because the main error code is in the lower 8-bits of the error code, theassigned value is designed so that its value as an 8-bit signed integer remains negative.
The error number (errno) has been removed.
(3) Object Attribute
The ITRON general object attribute is:
TA_NULL

0

Object attribute unspecified(4) Timeout Specification
The ITRON timeout specifications are as follows:
TMO_POL
TMO_FEVRTMO_NBLK0–1–2Polling
Waiting foreverNon-blocking

2.3.3 ITRON General Macros(1) Error Code Retrieving Macros
ER mercd = MERCD ( ER ercd )This macro retrieves the main error code from an error code.
ER sercd = SERCD ( ER ercd )This macro retrieves the sub error code from an error code.

2.3.4 ITRON General Static APIs
(1) File Inclusion
INCLUDE ( string ) ;This static API includes the file containing preprocessor macro definitions, the C language declarations, and the definitions necessary to interpret preprocessor constant
expressions and general constant expression parameters. The INCLUDE static API
must be specified in a system configuration file. The parameter string must be of aform that can be placed after the preprocessor directive “ #include” once the
INCLUDE static API is processed.
[Supplemental Information]
Examples of file inclusion using the static API are as follows:
INCLUDE ( "<itron.h>" ) ;INCLUDE ( "\"memory.h\"" ) ;48

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The reason string parameters are used is to prevent the file name from being expandedby the preprocessor before the system configuration file is passed to the configurator.

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Chapter 3 Concepts and Common
Definitions in µITRON4.0
3.1 Glossary of Basic Terms(1) Task and Invoking Task
The term “task” refers to a unit of concurrent processing. While program statements
inside a single task are executed sequentially, statements of different tasks are executed
concurrently. Multiple tasks are executed concurrently when seen from an application’s point of view. However, the tasks do not actually run in parallel but rather, they
are executed one by one under the control of the kernel, using time-sharing techniques.
The task that invokes a service call is called the “invoking task.”(2) Dispatching and Dispatcher
The act of switching the currently executing task on a processor with another, non-executing task is called “dispatching” (or “task dispatching”). The mechanism in the kernel that performs dispatching is called the “dispatcher” (or the “task dispatcher”).
(3) Scheduling and Scheduler
The process that determines which task is to be executed next is called “scheduling” (or“task scheduling”). The mechanism in the kernel that executes scheduling is called the“scheduler” (or the “task scheduler”). In typical implementations, the scheduler is
included in service call routines and/or in the dispatcher.
(4) Context
The environment in which a program executes is generally called the program’s “context.” When two programs have the same context, then at least the processor mode andstack space should be the same. The term context, however, is from an application’s
point of view and there can be tasks which execute in independent contexts but actually
run in the same processor mode and the same stack space.
(5) Precedence
The criterion used to determine the order of program execution is called “precedence.”
In principle, when a higher precedence program becomes executable, it will begin executing in place of the currently executing lower precedence program.

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Ver. 4.00.00[Supplemental Information]
A “priority” is a parameter given by an application to control the order of task execution and the order of message delivery, while precedence is used to clarify the order ofprogram execution in this specification. The precedence between tasks is determinedby the task priorities.

3.2 Task States and Scheduling Rule3.2.1 Task States
Task states are classified into five broad categories. The blocked state category can befurther broken down into three sub-states. The RUNNING state and the READY state
are both generically referred to as the runnable state.
(a) RUNNING state
When a task is in the RUNNING state, the task is currently executing. When
non-task contexts, such as interrupt handlers, take over execution, the task that was
executing remains in the RUNNING state unless otherwise specified.
(b) READY state
When a task is in the READY state, the task is ready to execute but it cannot,
because a task with higher precedence is already executing. In other words, thetask can execute at any time once its precedence becomes the highest among thetasks in the runnable state.
(c) Blocked state
When a task is in the blocked state, the task cannot execute because the conditions
necessary for its execution have not yet been met. The task is waiting for specificconditions to be met before it can continue execution. When a task enters theblocked state, the task’s execution environment including the program counter andregisters are saved. When the task resumes executing from the blocked state, theprogram counter and registers are restored to their previous values. The blocked
state can be further classified into three sub-states:(c.1) WAITING state
When a task is in the WAITING state, the execution is blocked due to the invocationof a service call. The service call specifies the conditions that must be met before
the task continues execution.
(c.2) SUSPENDED state
When a task is in the SUSPENDED state, the task has been forcibly made to halt
execution by another task. However, the invoking task can also suspend itself in theµITRON4.0 Specification.
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When a task is in the WAITING-SUSPENDED state, the task is both waiting for a
condition to be met and suspended. A task in the WAITING state will be moved to
the WAITING-SUSPENDED state if there is a request to move it to the SUSPENDED state.
(d) DORMANT state
When a task is in the DORMANT state, the task is either not yet executing or has
already finished. The context information of a task will not be saved while the task
is in the DORMANT state. When a task is activated from the DORMANT state, itwill begin executing from the task’s start address. The contents of the registers
when the task begins executing are not guaranteed unless otherwise specified.
(e) NON-EXISTENT stateThis indicates a virtual state where the task in question does not exist in the system,
either because it has not yet been created or because it has already been deleted.
There may be other transitional states, depending on the implementation, that cannot
be classified into any states listed above. (see Section 3.5.6).
If a task which has been moved to the READY state has higher precedence than thetask in the RUNNING state, the lower precedence task will be moved to the READY
state and the higher precedence task will be dispatched and moved to the RUNNING
state. In this case, we say that the task that was in the RUNNING state has been preempted by the task that was moved to the RUNNING state. Even if the functionaldescription of a service call mentions that “a task is moved to the READY state,” it
may be moved directly to the RUNNING state depending on the task precedence.
Task activation means that a task in the DORMANT state is moved to the READY
state. All states other than the DORMANT state and the NON-EXISTENT state are
generically referred to as active states. Task termination means that a task in the active
state is moved to the DORMANT state.
Releasing a task from waiting means that if the task is in the WAITING state, it will be
moved to the READY state, and if the task is in the WAITING-SUSPENDED state, thetask will be moved to the SUSPENDED state. Resuming a suspended task mean that if
the task is in the SUSPENDED state, it will be moved to the READY state, and if thetask is in the WAITING-SUSPENDED state, it will be moved to the WAITING state.
Figure 3-1 shows the task state transitions for typical implementations. There may beother state transitions, depending on the implementation, that are not shown in this figure.
[Supplemental Information]
The WAITING state and the SUSPENDED state are independent of each other. Therefore a request to move a task to the SUSPENDED state does not affect the release condition of the task. In other words, a waiting task’s release condition does not change
whether or not the task is in the WAITING state or in the WAITING-SUSPENDED

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dispatch

READY

preempted
release fromwaiting

AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA
AAAA

RUNNING

wait

WAITINGsuspendresumeWAITINGSUSPENDED
release fromwaitingsuspendsuspend

SUSPENDED
resumeforcibly
terminateactivate

DORMANT
forcibly terminate

AAAAA
AAAAA
AAAAA

exit

deletecreateNON-EXISTENT

exit and delete

Figure 3-1. Task State Transitions
state. Therefore, if a task that is waiting for a resource (such as a semaphore resource
or a memory block) is suspended and moved to the WAITING-SUSPENDED state, thetask will still acquire the resource under the same conditions as it would in the WAITING state.
[Differences from the µITRON3.0 Specification]
The task state names are now in the adjective form. They have been renamed from
RUN to RUNNING, from WAIT to WAITING, from SUSPEND to SUSPENDED, andfrom WAIT-SUSPEND to WAITING-SUSPENDED.
An invoking task can now move itself to the SUSPENDED state. This feature facilitates implementing APIs that do not distinguish self-suspension from suspension ofother tasks (such as those for POSIX and Java threads) on µITRON4.0 Specification
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Ver. 4.00.00[Rationale]
The ITRON Specifications distinguishes the WAITING state from the SUSPENDED
state because a task can exist in both states at the same time. Defining the overlappedstate as the WAITING-SUSPENDED state makes the task state transition clearer andmakes the understanding of service calls easier. Because tasks in the WAITING statecannot invoke service calls, they will never be in more than one kind of WAITING
state, e.g. sleeping while waiting for a semaphore resource. In the ITRON Specifications, the SUSPENDED state is the only blocked state that can be caused by othertasks. Tasks may be suspended multiple times by other tasks. This is handled throughnesting of the suspend requests.

3.2.2 Task Scheduling Rules
In the ITRON Specification, the preemptive, priority-based task scheduling is conducted based on the priorities assigned to tasks. If there are a number of tasks with thesame priority, scheduling is conducted on a “first come, first served” (FCFS) basis.
This task scheduling rule is defined using the precedence between tasks based on taskpriorities as described below.
If more than one runnable task exists, the highest precedence task will be in the RUNNING state, and the rest in the READY state. Among the tasks with different priorities, the task with the higher priority has higher precedence. Among tasks of the samepriority, the task that entered the runnable (RUNNING or READY) state earlier has
higher precedence. However, the precedence between tasks of the same priority may
change due to the invocation of some service calls.
When a task is given precedence over any other runnable tasks, a dispatch will occur
immediately, and the task in the RUNNING state will be switched with the new task.
However, when the system is in a state where dispatching does not occur, the switch of
the task in the RUNNING state will wait until dispatching is allowed.
[Supplemental Information]
In the ITRON Specifications, as long as the highest precedence task is in the runnable
state, no lower precedence tasks are allowed to execute. No other tasks will execute
unless the highest precedence task cannot be executed for some reason, such as being
placed in the WAITING state. In this respect, the scheduling rule of the ITRON Specifications differs entirely from TSS (Time-Sharing Systems), which attempts to execute
multiple tasks as equally as possible. However, the precedence between tasks with thesame priority may be modified through service calls. Applications can execute in around-robin fashion, a common scheduling system for TSS, by using those service
calls.
Figure 3-2 shows that among tasks of the same priority, the task that becomes runnable
first has the highest precedence. Figure 3-2 (a) shows the precedence between tasks

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precedence
priority 1

Task Apriority 2

Task Bpriority 3

Task E

Task CTask D(a) Precedence in the first stateprecedence
priority 2

Task Bpriority 3

Task E

Task CTask D(b) Precedence after Task B becomes the RUNNING stateprecedence
priority 2

Task Cpriority 3

Task E

Task D(c) Precedence after Task B becomes the blocked stateprecedence
priority 2

Task Cpriority 3

Task E

Task D

Task B(d) Precedence after Task B is released from waiting
Figure 3-2. Precedence between Tasks
after Task A (priority 1), Task E (priority 3), and Task B, C and D (priority 2), havebeen activated in this order. Task A, with the highest precedence, is in the RUNNING
state.
When Task A terminates, Task B, the task with the second highest precedence, moves
to the RUNNING state (Figure 3-2 (b)). If Task A is reactivated, Task B will be preempted and return to the READY state. However, since Task B will be in the runnable
state before Task C and Task D, it will have the highest precedence among the tasks
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with the same priority. This means that the priorities between tasks will go back to thestate shown in Figure 3-2 (a).
When Task B changes from the runnable state to the WAITING state, the organizationof the tasks will change from Figure 3-2 (b) to Figure 3-2 (c). If Task B is released
from waiting, the priority of Task B will be the lowest among tasks of the same priority
because Task B becomes runnable after Task C and Task D. This state is illustrated in
Figure 3-2 (d).
To summarize, if a task in the READY state moves to the RUNNING state and thengoes back to the READY state, it will have the highest precedence among tasks of thesame priority. On the other hand, when a task in the RUNNING state moves to the
WAITING state, and then back to the READY state, the task will have the lowest precedence among the tasks of the same priority.
[Differences from the µITRON3.0 Specification]
The ready queue is a concept related to the implementation, so in the specification“precedence” is used instead of “ready queue” to describe the scheduling rule.
To reduce implementation dependencies, a task that is moved from the SUSPENDED
state to the READY state, will have the lowest precedence among the tasks of the samepriority.

3.3 Interrupt Process Model
3.3.1 Interrupt Handlers and Interrupt Service Routines
In the µITRON4.0 Specification, interrupt handlers and interrupt service routines areprocessing units started by external interrupts (simply called as interrupts below).
Basically, execution of an interrupt handler depend on the processor architecture.
Therefore, the interrupt handler, not the kernel, should be the one to control the Interrupt Request Controller (IRC). The implementation of an interrupt handler is implementation-defined because it generally depends on the processor interrupt architecture
and the IRC. An interrupt handler cannot be ported as is to a different system.
An interrupt service routine is a routine started by an interrupt handler. It can be implemented independently from the processor architecture and the IRC used. This meansthat there is no need for the interrupt service routine to control the IRC since the interrupt handler starting the interrupt service routine already controls the IRC.
The µITRON4.0 Specification defines the APIs to register an interrupt handler prepared by the application, such as DEF_INH, and the APIs to register an interrupt service routine, such as ATT_ISR. An implementation should provide either one set ofAPIs or both sets. If the APIs for registering an interrupt handler are provided, the kernel can provide a glue routine for the interrupt handler that includes processes to be

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done before and after the interrupt handler executes. Depending on the interrupt handler attribute, the interrupt handler can be started through the provided glue routine. If
only the APIs for registering an interrupt service routine are provided, the kernel must
provide the interrupt handler that starts the interrupt service routine. Although bothAPIs are allowed at the same time, the behavior when both APIs are used is implementation-defined.
Depending on the implementation, the kernel does not control interrupts with higher
priorities than a threshold priority level, including non-maskable interrupts. These
kinds of interrupts are called non-kernel interrupts. The method for defining thethreshold priority level is implementation-defined. No kernel service calls can be
invoked from interrupt handlers started by non-kernel interrupts. In this specification
document, the term “interrupt” and “interrupt handler” do not include non-kernel interrupts and interrupt handlers started by non-kernel interrupts, respectively.
Figure 3-3 shows the interrupt processing model in the µITRON4.0 Specification. This
figure only outlines a conceptual model. The actual method used to realize interrupt
processing depends on the application and implementation.

Interrupt handler
glue routine
External
interrupt

Interrupt
handler

Control of IRC

Interrupt service
routineA

B

returntask dispatch

Figure 3-3. Interrupt Processing Model[Supplemental Information]
The responsibilities of the interrupt handler glue routine include saving and restoring
registers used within the handler, switching stack space, task dispatching, and returningfrom the interrupt. The operations actually performed by the glue routine depend on
the implementation. The operations that are included in the glue routine and those that58

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are included in the interrupt handler prepared by the application are implementation-defined and determined by the interrupt handler attributes.
The responsibilities of the interrupt handler that starts interrupt service routines include
reading the cause of the interrupt from the IRC, branching based on the cause, clearing
the edge trigger, and clearing the in-service flag of the IRC. In addition, the CPU must
be unlocked before starting an interrupt service routine.
In order to reduce the overhead associated with an interrupt service routine, the interrupt handler glue routine and the interrupt handler can be merged. Interrupt service
routines can be directly embedded in-line within the interrupt handler.
[Standard Profile]
The Standard Profile requires support for either the APIs to register an interrupt handler
or the APIs to register an interrupt service routine.
[Rationale]Interrupt service routines are introduced to improve the portability of an application’s
interrupt processing. Interrupt handlers, which are less portable, remain so that a kernel can be provided that is independent of an IRC.

3.3.2 Ways to Designate an Interrupt
In the µITRON4.0 Specification, there are two ways to designate an interrupt: by using
an interrupt number and by using an interrupt handler number. In addition, an interrupt
service routine is identified by an ID number.
The interrupt handler number, INHNO type, is used to designate the interrupt that ishandled by an interrupt handler registered with the kernel. The designated interrupt
should be able to be determined without referencing the IRC. The interrupt handler
number corresponds to the interrupt vector number of the processor in typical implementations. When the processor does not have interrupt vectors, there may be only one
available interrupt handler number.
The interrupt number, INTNO type, is used to designate the interrupt that is handled byan interrupt service routine registered with the kernel. The interrupt number is also
used as a parameter to some service calls, such as dis_int and ena_int, to disable andenable each interrupt individually. Because starting an interrupt service routine andindividually disabling/enabling interrupts are executed by controlling the IRC, theinterrupt number corresponds to the interrupt request line of the IRC.
An interrupt service routine is bound to a specific interrupt request line from a device.
Since the interrupt request line to the IRC can be connected to more than one device,
more than one interrupt service routine can be registered to a single interrupt number.
If the interrupt designated by the interrupt number occurs, all interrupt service routines
bound to the interrupt number will be called one by one. The order in which the interrupt service routines are called is implementation-dependent. Multiple interrupt ser59

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vice routines bound to a single interrupt number are distinguished by interrupt service
routine ID numbers.
[Supplemental Information]
For the case when multiple devices are connected to a single interrupt request line to
the IRC, the devices may supply an interrupt vector number used by the processor todetermine the actual source of the interrupt. In this case, interrupt sources supplying
different vector numbers can have different interrupt numbers.

3.4 Exception Process Model
3.4.1 Exception Processing Framework
The µITRON4.0 Specification defines the CPU exception handling and the task exception handling functions.
A CPU exception handler is started when the processor detects an exception. A CPU
exception handler can be registered by the application for each kind of CPU exception.
The kernel can provide a glue routine for the CPU exception handler that includes processes to be done before and after the CPU exception handler executes. Depending on
the CPU exception handler attribute, the CPU exception handler can be started throughthe provided glue routine.
Because the CPU exception handlers are common to the whole system, the context andthe state at the point when the CPU exception occurred can be probed by the CPU
exception handler. When a CPU exception occurs within a task, the CPU exception
handler can let the task’s exception handling routine handle the exception if desired.
The task exception handling functions are used to stop the normal execution of thespecified task and to start the task’s exception handling routine. The task’s exception
handling routine is executed within the same context as the task. When returning fromthe task exception handling routine, the execution of the interrupted execution will continue. The application can register one task exception handling routine for each task.
The task exception handling functions will be explained in Section 4.3.
[Standard Profile]
The CPU exception handling routine and the task exception handler must be supported
in the Standard Profile.

3.4.2 Operations within a CPU Exception Handler
The implementation method of a CPU exception handler is implementation-defined,
because it generally depends on the processor exception handling architecture and thekernel implementation. A CPU exception handler cannot be ported to a different sys-60

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tem without changes.
The service calls that can be invoked in a CPU exception handler are implementation-defined. However, a CPU exception handler must be able to perform the operat i o n s d e s c r i b e d b e l ow. T h e m e t h o d t o p e r f o r m t h e s e o p e r a t i o n s i simplementation-defined.
A CPU exception handler must be able to:(a) Read the context and system state when the CPU exception occurred. The kernelmust provide a method to reference the system state information when the CPU
exception occurred that would normally be obtained through sns_yyy service
calls invoked just prior to the CPU exception.
(b) Read the task ID of the task in which the CPU exception occurred, if the exception
occurred while a task was executing.
(c) Request task exception handling. This operation is equivalent to invoking ras_tex
within the CPU exception handler.
If the exception occurs while the CPU is locked, it is not necessary to support (b) and(c).

3.5 Context and System State
3.5.1 Processing Units and Their Contexts
In the µITRON4.0 Specification, the kernel controls the execution of the following processing units:(a) Interrupt handlers(a.1) Interrupt service routines(b) Time event handlers(c) CPU exception handlers(d) Extended service call routines(e) Tasks(e.1) Task exception handling routines
Interrupt handlers and interrupt service routines execute in their own independent contexts. For the remainder of this section, the descriptions about interrupt handlers apply
to interrupt service routines as well, unless a specific description about interrupt service
routines is provided.
Time event handlers are started by a time trigger. There are three kinds of time event
handlers: cyclic handlers, alarm handlers, and overrun handlers. Time event handlers
execute in their own independent contexts. Cyclic handlers are explained in Section
4.7.2, alarm handlers are explained in Section 4.7.3, and overrun handlers are
explained in Section 4.7.4.

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A CPU exception handler executes in an independent context determined by the CPU
exception and by the context in which the CPU exception occurred.
Extended service call routines are registered by the application and are started by
invoking extended service calls. An extended service call routine executes in an independent context determined by the extended service call and by the context from which
the extended service call is invoked. Extended service call routines are explained in
Section 4.10.
Tasks execute in their own independent contexts. A task exception handling routine
executes in the associated task’s context. In the remainder of this section, the descriptions about tasks apply to task exception handling routines as well, unless a specificdescription about task exception handling routines is provided.
Kernel processes are not classified into the processing units mentioned above. The kernel processes include service call execution, the dispatcher, glue routines for interrupt
handlers (or interrupt service routines), and glue routines for CPU exception handlers.
The context in which the kernel processes execute is not specified because it does notaffect the behavior of the application.
[Differences from the µITRON3.0 Specification]
The term “time event handler” is now used instead of “timer handler.” The term
“extended service call routine” is now used instead of “extended SVC handler.”

3.5.2 Task Contexts and Non-Task Contexts
Contexts that can be regarded as a part of a task are generically called task contexts,
while other contexts are generically called non-task contexts.
Contexts in which tasks execute are classified as task contexts. Contexts in whichinterrupt handlers and time event handlers execute are classified as non-task contexts.
Contexts for CPU exception handlers and for extended service call routines depend on
the contexts where they occur or where they are invoked. These contexts are defined
below.
When CPU exceptions occur in task contexts, the CPU exception handlers can execute
either in task contexts or in non-task contexts. In this case, the context in which a CPU
exception handler executes is implementation-defined. When CPU exceptions occur in
non-task contexts, the CPU exception handlers execute in non-task contexts.
When extended service calls are invoked from task contexts, the extended service routines execute in task contexts. When extended service calls are invoked from non-task
contexts, the extended service routines execute in non-task contexts.
In the µITRON4.0 Specification, service calls that can be invoked in task contexts andservice calls that can be invoked in non-task contexts are distinguished from each other.
The invocation of service calls in non-task contexts is described in Section 3.6.
The service calls that can move the invoking task to the blocked state and the service
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calls where the invoking task are implicitly specified may not be invoked from non-task
contexts. If such service calls are invoked, an E_CTX error is returned. Using theparameter TSK_SELF (= 0), which designates the invoking task as a parameter of theservice call, is also prohibited from non-task contexts. If TSK_SELF is used from
non-task contexts, an E_ID error is returned.
[Supplemental Information]
As mentioned in Section 3.5.3, dispatching does not occur during a CPU exception
handler execution, because the precedence of the CPU exception handler is higher thanthe precedence of the dispatcher. Therefore, in implementations where the CPU exception handler executes within task contexts, the behavior of service calls that may movethe task to the blocked state is undefined in this specification. If an error should bereported under these conditions, an E_CTX error is returned.
[Differences from the µITRON3.0 Specification]
The terms “task contexts” and “non-task contexts” are now used instead of “task portions” and “task-independent portions.” The term “transitional state” has been
removed because the context in which the kernel is executed is not specified. In theµITRON4.0 Specification, the concept of quasi-task portions is undefined and isincluded in task contexts, because the processor mode is not specified.

3.5.3 Execution Precedence and Service Call Atomicity
In the µITRON4.0 Specification, the precedence for executing each processing unit andthe dispatcher is specified as follows:(1) Interrupt handlers, time event handlers, CPU exception handlers(2) Dispatcher (one of the kernel processes)(3) Tasks
The precedence of interrupt handlers is higher than the precedence of the dispatcher.
The precedence between interrupt handlers and interrupt service routines is implementation-defined, depending on interrupt priorities.
The precedence of time event handlers is implementation-defined. However, time
event handlers cannot have higher precedence than interrupt handlers invoking
isig_tim, and it must be higher than the precedence of the dispatcher.
The precedence of CPU exception handlers is higher than the precedence of the processing unit where the CPU exception occurs and higher than the precedence of thedispatcher. The precedence of CPU exception handlers relative to the precedence ofinterrupt handlers and time event handlers is implementation-defined.
The precedence of extended service call routines is higher than the precedence of theprocessing unit that invokes the extended service calls and is lower than the precedenceof any processing unit that has a higher precedence than the invoking processing unit.

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The precedence of tasks is lower than the precedence of the dispatcher. The relative
precedence of tasks is defined by the task scheduling rule.
Basically, kernel service calls are executed atomically and the state of ongoing service
call processes is invisible. However, the implementation may choose to modify thisbehavior to improve system response. In this case, service call operation must still
appear to be executed atomically as far as the application can determine using service
calls. This behavior is called the service call atomicity guarantee. Service call atomicity may be difficult to guarantee while maintaining a high level of response with implementation-specific functions not covered in this specification. If this is so, thenloosening the principle of service call atomicity is permitted.
When kernel service calls are executed atomically, their precedence is highest. Whenthe atomicity is loosened as described above, the precedence of service call processes
is implementation-dependent as long as their precedence is higher than the processing
unit invoking the service calls.
Other kernel processes than service call processes such as the dispatcher, glue routines
for interrupt and exception handler are treated similarly.
[Standard Profile]
The Standard Profile requires service calls that are part of the Standard Profile must be
guaranteed to operate atomically.
[Supplemental Information]
Since the precedence of the dispatcher is lower than the precedence of interrupt handlers, dispatching does not occur until all activated interrupt handlers are processed.
This was called the “delayed dispatching” rule. The same applies to time event handlers and CPU exception handlers.

3.5.4 CPU Locked StateThe CPU state of the system is in either the locked or unlocked state. In the CPU
locked state, interrupt handlers (except for those started by a non-kernel interrupt) andtime event handlers are not started and dispatching does not occur. The CPU locked
state can be considered as the state in which the precedence of the executing processing
unit is highest. There might be a transitional state that is neither the CPU locked state
nor the CPU unlocked state, depending on the implementation.
The transition to the CPU locked state is called “locking the CPU,” while the transition
to the CPU unlocked state is called “unlocking the CPU.”In the CPU locked state, the following service calls can be invoked:
loc_cpu / iloc_cpu
unl_cpu / iunl_cpu
sns_ctx

lock the CPU
unlock the CPU
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reference CPU statereference dispatching statereference dispatch pending statereference task exception handling state

where loc_cpu/iloc_cpu means that loc_cpu may be called from task contexts andiloc_cpu from non-task contexts (the same rule applies to unl_cpu/iunl_cpu). The
behavior of other service calls invoked from a CPU locked state is undefined. When anerror should be reported, an E_CTX error will be returned.
The CPU state is implementation-dependent after an interrupt handler starts (either in
the CPU locked state, in the CPU unlocked state, or in a transitional state). However, it
is implementation-defined how to enter the CPU unlocked state in interrupt handlers.
It is also implementation-defined how to return correctly from interrupt handlers after
the system has entered the CPU unlocked state. The behavior is undefined when interrupt handlers do not return according to the method specified by the implementation.
The system is in the CPU unlocked state after interrupt service routines and time event
handlers start. When returning from these routines/handlers, the system must be in the
CPU unlocked state. The behavior is undefined when returning from these routines/
handlers in the CPU locked state.
The start of and the return from CPU exception handlers do not change the CPU state.
In other words, after CPU exception handlers start, the system is in the CPU locked(unlocked) state when the CPU exception occurs in the CPU locked (unlocked) state.
When the CPU state is changed in CPU exception handlers, it should be returned to theprevious state before returning from the CPU exception handlers. The behavior isundefined when returning from CPU exception handlers without returning to the previous state.
The start of and the return from extended service call routines do not change the CPU
state. In other words, after extended service call routines start, the system is in the
CPU locked (unlocked) state when the extended service calls are invoked in the CPU
locked (unlocked) state. After returning from the extended call routines, the CPU stateremains the same as set by the routines.
After tasks start, the system is in the CPU unlocked state. When tasks exit, the system
must be in the CPU unlocked state. The behavior is undefined when tasks exit while in
the CPU locked state.
The start of and the return from task exception handling routines do not change theCPU state. However, it is not specified whether task exception handling routines arestarted in the CPU locked state. After returning from the task exception handling routines, the CPU state remains the same as set by the routines.
[Supplemental Information]
Interrupts are usually, but not always, allowed in the CPU unlocked state.

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Ver. 4.00.00[Differences from the µITRON3.0 Specification]
The meaning of the CPU state has changed. In the µITRON3.0 Specification, the CPU
locked state was considered the state where interrupts and task dispatching were disabled. However, in the µITRON4.0 Specification, the CPU locked state is treated conceptually as a state independent of interrupts and task dispatching. In the CPU locked
state only a few service calls can be invoked.

3.5.5 Dispatching Disabled StateThe dispatching state of the system is either disabled or enabled. Dispatching does notoccur in the dispatching disabled state. The dispatching disabled state can be considered as the state in which the precedence of the executing processing unit is higher thanthat of the dispatcher. There might be a transitional state that is neither the dispatching
disabled state nor the dispatching enabled state, depending on the implementation.
The transition to the dispatching disabled state is called “disabling dispatching,” while
the transition to dispatching enabled state is called “enabling dispatching.”
In the dispatching disabled state, service calls that can be invoked from task contexts
have the following restrictions. While in the dispatching disabled state, the behavior
caused by invoking service calls that can move the invoking task to the blocked state isundefined, unless otherwise specified. When an error should be reported, an E_CTX
error will be returned. On the other hand, service calls that can be invoked from
non-task contexts do not have restrictions even in the dispatching disabled state.
The start of and the return from interrupt handlers, interrupt service routines, time
event handlers, and CPU exception handlers do not change the dispatching state. In
other words, after these handlers/routines start, the system is in the dispatching disabled (enabled) state when these handlers/routines start in the dispatching disabled(enabled) state. When the dispatching state is changed in these handlers/routines, it
should be returned to the previous state before returning from these handlers/routines.
The behavior is undefined when returning from these handlers/routines without returning to the previous state.
The start of and the return from the extended service call routines do not change thedispatching state. In other words, after the extended service call routines start, the system is in the dispatching disabled (enabled) state when the extended service call routines are invoked from the dispatching disabled (enabled) state. After returning fromthe extended call routines, the dispatching state remains the same as set by the routines.
After tasks start, the system is in the dispatching enabled state. When tasks exit, thesystem must be in the dispatching enabled state. The behavior is undefined when tasks
exit in the dispatching disabled state.
The start of and the return from the task exception handling routines do not change thedispatching state. In other words, after task exception handling routines start, the sys-

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tem is in the dispatching disabled (enabled) state when the task exception handling routines start from the dispatching disabled (enabled) state. After returning from the task
exception handling routines, the dispatching state remains the same as set by the routines.
The dispatching state is treated independent of the CPU state.
[Supplemental Information]
The restriction that behavior is undefined when service calls that can move the invoking task to the blocked state are invoked while in the dispatching disabled state applies
to a service call as a whole, unless otherwise specified. For example, service calls forpolling, e.g. pol_sem, can be invoked in the dispatching disabled state because there
is no possibility that the invoking task will enter the WAITING state. On the other
hand, the behavior of service calls that may cause a task to enter the WAITING state,e.g. twai_sem, is undefined even if they are invoked with TMO_POL (polling) in thetimeout parameter.
There are no service calls that change the dispatching state in non-task contexts in theµITRON4.0 Specification. Therefore, it is impossible to change the dispatching state
within interrupt handlers and time event handlers unless an implementation-specificextension is provided. The same rule applies to CPU exception handlers when they are
executed in non-task contexts.
The dispatching state is treated independently from the CPU state. Therefore, forexample, if the system is in the dispatching disabled state and the CPU state changes
from the locked state to the unlocked state, the system remains in the dispatching disabled state. The dispatching state can still be sensed while the system is in the CPU
locked state.
[Differences from the µITRON3.0 Specification]
The meaning of the dispatching disabled state has been changed. The dispatching stateis defined as a state treated independently of the CPU state.

3.5.6 Task State during Dispatch Pending State
Dispatching does not occur during execution of processing units with higher precedence than that of the dispatcher, and while in the CPU locked state or in the dispatching disabled state. These three conditions are collectively called the dispatch pending
state. The task states in the dispatch pending state are defined below.
In the dispatch pending state, even in the situation where the task in the RUNNING
state should be preempted, the task that should run will not be dispatched. The dispatch for the task that should run will be pending until the system is in a state where
dispatching can occur. While dispatching is pending, the task that has been runningremains in the RUNNING state, while the task waiting for dispatching remains in the
READY state.
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Task states during the dispatch pending state can be affected by implementation-specific extensions. More precisely, extensions may allow non-task contexts to invoke service calls that move the task in the RUNNING state to the SUSPENDED state or the
DORMANT state. In addition, extensions may allow the service calls to move theinvoking task to the SUSPENDED state while in the dispatching disabled state. Task
states for these cases are described below.
When the task in the RUNNING state is to be moved to the SUSPENDED state or the
DORMANT state, the transition is pending until the system state allows dispatching tooccur. While the state transition is pending, the task that has been in the RUNNING
state is considered to be in a transitional state. The treatment of a task in this transitional state is implementation-dependent. The task that should be in the RUNNING
state remains in the READY state until the dispatch occurs.
[Supplemental Information]
Figure 3-4 explains the task state during the dispatch pending state. Suppose that Task
B is activated from the interrupt handler that was invoked by the interrupt that occurred
during execution of Task A when the priority of Task B is higher than the priority of
Task A. Since the precedence of the interrupt handler is higher than that of the dispatcher, the system is in the dispatch pending state while the interrupt handler is executing. Therefore dispatching does not occur. When the interrupt handler execution
terminates, the dispatcher is executed and the task that should run switches from Task
A to Task B.

Task B(high priority)

Dispatcher

Interrupt
handler

READY

iact_tsk( Task B )RUNNINGREADY

RUNNING

Task A(low priority)

Figure 3-4. Dispatch Pending State and Task States
Even after Task B is activated, Task A is in the RUNNING state and Task B is in the
READY state until the dispatcher is started. After the dispatcher executes, Task B is in
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the RUNNING state, and Task A is in the READY state. Because the dispatcher should
be executed atomically, task states during the dispatcher execution are not specified inthis specification.

3.6 Service Call Invocation from Non-Task Contexts
3.6.1 Service Calls that can be Invoked from Non-Task Contexts
Service calls that can be invoked from non-task contexts have the letter “i” added to thebeginning of their names so they can be distinguished from service calls that can be
invoked from task context. Service calls that can be invoked from both non-task contexts and task contexts have a different naming convention as described below. In otherwords, the service calls are classified into the following three categories:(a) Service calls for non-task contexts
Service calls whose names begin with “i” are called service calls for non-task contexts.
They may be invoked from non-task contexts.
[Supplemental Information]
The following service calls belong to this category:
iact_tsk
iwup_tsk
irel_waiiras_tex
isig_sem
iset_flg
ipsnd_dtq
ifsnd_dtq
isig_tim
irot_rdq
iget_tid
iloc_cpu
iunl_cpu

activate task
wakeup task
release task from waitingraise task exception handlingrelease semaphore resource
set eventflag
send to data queue (polling)
forced send to data queue
supply time tickrotate task precedence
reference task ID in the RUNNING state
lock the CPU
unlock the CPU

The behavior of the service calls for non-task contexts invoked from task contexts isundefined. When an error should be reported, an E_CTX error is returned.
(b) Service calls that can be invoked from any contexts
Service calls whose names are of the form sns_yyy can be invoked from any contexts. They may be invoked from both task contexts and non-task contexts.
[Supplemental Information]
The following service calls belong to this category:
sns_ctxreference contexts
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reference CPU statereference dispatching statereference dispatch pending statereference task exception handling state(c) Service calls for task contexts
The remaining service calls are called service calls for task contexts. They may be
invoked from task contexts.
The behavior of the service calls for task contexts invoked from non-task contexts isundefined. When an error should be reported, an E_CTX error is returned.
[Differences from the µITRON3.0 Specification]
Service calls for non-task contexts are specified to have names that begin with “i.”Invoking service calls for task contexts from non-task contexts is permitted as animplementation-specific extension.

3.6.2 Delayed Execution of Service Calls
The execution of service calls invoked from non-task contexts may be delayed at mostuntil the processing units that have higher precedence than the dispatcher have terminated. This makes it possible to guarantee the atomicity of service calls without disabling interrupts for too long. This is called delayed execution of service calls.
However, the following service calls are not allowed to have their execution delayed:
iget_tid
iloc_cpu
iunl_cpu
sns_ctx
sns_loc
sns_dspsns_dpnsns_texreference task ID in the RUNNING state
lock the CPU
unlock the CPU
reference contexts
reference CPU statereference dispatching statereference dispatch pending statereference task exception handling state

When the service calls have their execution delayed, the processing order of the service
calls must correspond to the order in which the service calls were invoked, excluding
those service calls that are not allowed to have their execution delayed.
There are situations in which the service calls that are invoked from non-task contexts
and that have their execution delayed cannot return some error codes. This is because
the detection of some errors depends on the target object’s state and the object’s statecannot be referenced when the service call’s execution is delayed. In these situations,
E_OK can be returned instead of the error code that would be returned for non-delayed
execution. The error codes that may not be returned when execution is delayed aredefined for each service call.
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cient memory to store a service call for delayed execution, the service call must return
an E_NOMEM error.
[Supplemental Information]
The point at which the service call executes after having its execution delayed is up to
the implementation as long as the behavior of the delayed execution is the same as
described by the specification. A specific case is where service calls invoked during the
dispatch pending state may be delayed until the system enters a state where dispatching
can occur. Note that there are situations in which iras_tex must be executed even in
the dispatching disabled state. See the supplemental information of iras_tex for moredetails.
When service calls that have their execution delayed return E_OK, it must be guaranteed that those service calls will be executed later.
[Differences from the µITRON3.0 Specification]
The specification regarding delayed execution of service calls has been clarified.

3.6.3 Adding Service Calls that can be Invoked from Non-Task
Contexts
When a service call for task contexts with the name xxx _ yyy (or zxxx _ yyy ) isdefined in the µITRON4.0 Specification, an implementation may add a service call for
non-task contexts which has the same functionality. In this case the name of the newservice call should be ixxx_yyy (or izxxx_yyy) regardless of the rule that the namesof implementation-specific service calls should begin with the letter “v.” The new service call is still considered to have the same functionality even when some error codes
are not returned due to delayed execution of the service call invoked from non-task
contexts.
When a service call for task contexts is made invokable from non-task contexts using
its original name as an implementation-specific extension, the implementation mustalso provide a service call where the letter “i” is added at the beginning of its name thatis invokable from non-task contexts. On the other hand, when a service call for
non-task contexts is made invokable from task contexts using its original name as animplementation-specific extension, the implementation must also provide a service callwhere the letter “i” is removed from the beginning of its name that is invokable fromtask contexts.
These rules apply to implementation-specific service calls as well. When there is an
implementation-specific service call with the name vxxx_yyy and a service call withthe same functionality can be invoked from non-task contexts, it must be invokablewith the name ivxxx_yyy.

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3.7 System Initialization Procedure
System initialize procedure is modeled as follows (Figure 3-5):

Reset

Hardware-dependent
initialization process

Kernel initialization
process

Static API process– Object registrations– Execution of initialization routines

Start of kernel operation– System time initialization– Enabling interrupts– Beginning task executions

Figure 3-5. System Initialization Procedure
The hardware-dependent initialization process is executed after the system is reset.
The application prepares the hardware-dependent initialization process, which is outside of the kernel’s control. The kernel initialization process is called at the end of the
hardware-dependent initialization process. The method used to call the kernel initialization process is implementation-defined.
Once the kernel initialization process is called, the kernel itself, such as the kernel’sinternal data structures, is initialized. Then, the static APIs, such as object registrations, are processed. The static APIs, except for ATT_INI, are processed in the order
described in the system configuration file. The method used to handle errors detectedduring the static API processes is implementation-defined.
The processing of the static APIs includes the execution of initialization routines. The
initialization routines are prepared by the application and registered with the kernel byusing ATT_INI. The initialization routines are executed with all interrupts disabled
except for non-kernel interrupts. Disabling non-kernel interrupts is implementation-defined. Allowing initialization routines to invoke service calls and which service
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tive order between the execution of initialization routines and the processing of otherstatic APIs is implementation-defined.
After the processing of the static APIs, the kernel operation is started. Specifically,tasks begin execution. At this point interrupts are enabled for the first time and the system time is initialized to 0.
The above description provides only a conceptual model. The real system initialization
procedure may be optimized in an implementation-dependent manner as long as the
behavior conforms to this conceptual model.

3.8 Object Registration and Release
An object identified by an ID number is registered to the kernel by a static API( CRE_ YYY ) or by a service call (cre_ yyy ) that creates the object. An object isreleased from the kernel by a service call (del_yyy) that deletes the object. After an
object is deleted, a new object can be created with the same ID number. When an
object is created, the ID number and the necessary information for creating the object
are specified. When an object is deleted, the ID number for the object is specified.
The maximum number of objects and the range of the ID numbers that can be registered are implementation-defined. The maximum number of objects that can be created by using service calls and the procedure to designate the range of ID numbers arealso implementation-defined.
When a static API (ATT_YYY) attaches an object to the kernel, it creates and registers
the object without specifying an ID number. Objects registered in this way cannot bereferred by ID numbers because the created objects do not have ID numbers, whichmeans that objects created in this way cannot be deleted.
The service call that creates an object and assigns an ID number automatically( acre_ yyy ) assigns the object ID number by selecting an ID number that is notalready associated with an object. The ID number assigned to the created object isreturned to the application as the return value. The ID number assigned in this way islimited to a positive number because a negative return value from a service call indicates an error occurred. If there is no ID number that can be assigned, the service callreturns an E_NOID error.
The method an implementation employs to designate the range of ID numbers available for automatic assignment is implementation-defined. The method used to automatically assign available ID numbers to objects is implementation-dependent.
A synchronization and communication object can be deleted even if there is a task
waiting for a condition to be met associated with the object. In this case, the task that is
waiting for the condition associated with the deleted object is released from waiting.
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the released task. If more than one task is waiting, the tasks are released from waitingin the order in which they reside in the wait queue for the synchronization and communication object. Therefore, among tasks with the same priority that are moved into the
READY state, tasks closer to the head of the wait queue have higher precedence. Incase the synchronization and communication object has multiple wait queues, the orderthat tasks are released from different wait queues is implementation-dependent.
[Standard Profile]
The Standard Profile requires an implementation to support at least ID numbers from 1
to 255. Also, the Standard Profile requires that at least 255 objects can be registered for
objects that are referenced by ID numbers and are part of the Standard Profile.

3.9 Description Format for Processing Unit
The µITRON4.0 Specification specifies the format for writing each of the following
processing units in the C language: interrupt service routines, time event handlers(cyclic handlers, alarm handlers, overrun handlers), extended service call routines,
tasks, and task exception handling routines. If TA_HLNG (processing unit started
through a high-level language interface) is specified as the object attribute when theprocessing unit is registered with the kernel, the processing unit is started assuming it is
written in the specified format.
On the other hand, the µITRON4.0 Specification does not specify the format for writing processing units in assembly language. If TA_ASM (processing unit started
through an assembly language interface) is specified as the object attribute when theprocessing unit is registered with the kernel, the processing unit is started assuming it is
written in the format specified by the implementation.
The format for writing interrupt handlers and CPU exception handlers and the object
attributes used to register them with the kernel are implementation-defined and are notspecified in the µITRON4.0 Specification.
[Supplemental Information]
The µITRON4.0 Specification does not specify the service call that returns from interrupt handlers (ret_int in the previous specifications). This is not because the process
executed by ret_int in the previous specifications is no longer needed, but rather
because how to write interrupt handlers is now implementation-defined. There may be
a case where a service call corresponding to ret_int may be provided by an implementation. This also applies to returning from CPU exception handlers.
The µITRON4.0 Specification does not specify the service call that returns from time
event handlers (ret_tmr in the previous specifications). This is not because the process
executed by ret_tmr in the previous specifications is no longer needed, but rather
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language. There may be a case where a service call corresponding to ret_tmr is provided by an implementation in order to return from time event handlers written inassembly language. This also applies to returning from interrupt service routines,
extended service call routines, and task exception handling routines.
[Differences from the µITRON3.0 Specification]
The µITRON4.0 Specification specifies the format for writing each processing unit in
the C language, but does not specify service calls (ret_yyy) for returning from processing units, because they are only needed when the processing units are written inassembly language.

3.10 Kernel Configuration Constants and Macros
Applications use kernel configuration constants and macros to reference the kernel
configuration in order to improve application program portability. The method used todefine kernel configuration constants and macros is implementation-dependent as longas they can be referenced from an application program
Kernel configuration constants and macros are not defined when functions related tothem are not supported.
[Supplemental Information]
Kernel configuration constants and macros may be defined as fixed values in kernel
header files or may be generated by a configurator. Alternatively they may be definedin header files prepared by the application and then used to configure the kernel.
[Differences from the µITRON3.0 Specification]
The µITRON4.0 Specification newly introduces kernel configuration constants andmacros.

3.11 Kernel Common Definitions
3.11.1 Kernel Common Constants(1) Object Attributes
TA_HLNG

0x00

TA_ASM

0x01

TA_TFIFO
TA_TPRI

0x00
0x01

Start a processing unit through a high-level language
interface
Start a processing unit through an assembly language
interface
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TA_MPRI

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0x02

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The values of TA_HLNG and TA_ASM have been exchanged.
(2) Main Error Codes Used in Kernel
The kernel uses the main error codes specified in Section 2.3.2, except for the threecodes, E_CLS, E_WBLK, and E_BOVR.
[Standard Profile]In the Standard Profile the following main error codes are generated and must be
detected:
E_OBJ
E_QOVR
E_RLWAIE_TMOUT

Object state error
Queue overflow
Forced release from waiting
Polling failure or timeout

Applications that need to be portable across kernels adhering to the Standard Profile
must not depend on detecting errors beyond those listed above.
[Supplemental Information]
In the Standard Profile the following main error codes are not generated or need not be
detected:(a) Error codes not used by the kernel
E_CLS, E_WBLK, E_BOVR(b) Error codes not generated by Standard Profile functions
E_OACV, E_NOID, E_NOEXS, E_DLT(c) Error codes that are implementation-dependent
E_SYS, E_RSFN, E_NOMEM(d) Error codes whose detection can be omitted
E_NOSPT, E_RSATR, E_PAR, E_ID, E_CTX, E_MACV, E_ILUSE(3) Service Call Function Codes
Function codes ranging from (–0xe0) to (–0x05) are assigned to kernel service calls.
However, a function code is not assigned to cal_svc. The assignment of function
codes is specified in each function in Chapter 4.
Function codes within the range from (–0xe0) to (–0x05) that are not assigned in thespecification are reserved for the kernel function extensions in the future. Function
codes ranging from (–0x100) to (–0xe1) can be used for implementation-specific service calls. Function codes ranging from (–0x200) to (–0x101) are reserved for kernel
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function extensions in the future. However, they can be used for implementation-specific service calls if needed.
[Differences from the µITRON3.0 Specification]
The values of function codes have been reassigned.
[Rationale]
Function codes of service calls included in the Standard Profile range from (–0x80) to(–0x05) in order to fit within 8 bits.
(4) Other Kernel Common Constants
TSK_SELF
TSK_NONE00

Specifying invoking task
No applicable task

[Differences from the µITRON3.0 Specification]
TSK_NONE has been added. In the µITRON3.0 Specification, FALSE (= 0) wasused when there was no applicable task available.

3.11.2 Kernel Common Configuration Constants(1) Priority Range
TMIN_TPRI
TMAX_TPRI

Minimum task priority (= 1)
Maximum task priority

TMIN_MPRI
TMAX_MPRI

Minimum message priority (= 1)
Maximum message priority[Standard Profile]
These kernel configuration constants must be defined in the Standard Profile.
TMAX_TPRI must not be less than 16 and TMAX_MPRI must not be less than
TMAX_TPRI.
[Supplemental Information]
Although TMIN_TPRI and TMIN_MRI are fixed as 1 in this specification, implementation-specific extensions may configure the kernel to use a value other than 1.
(2) Version Information
TKERNEL_MAKER
TKERNEL_PRID
TKERNEL_SPVER
TKERNEL_PRVER

Kernel maker code
Identification number of the kernel
Version number of the ITRON Specification
Version number of the kernel[Standard Profile]
These kernel configuration constants must be defined in the Standard Profile.
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µITRON4.0 Specification

Ver. 4.00.00[Supplemental Information]
See the functional description of ref_ver for the constant values that represent version
information.

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Chapter 4 µITRON4.0 Functions
4.1 Task Management Functions
Task management functions provide direct control of task states and reference to thetask states. Task management functions include the ability to create and delete a task,
to activate and terminate a task, to cancel activation requests, and to reference the stateof a task. A task is an object identified by an ID number. The ID number of a task iscalled the task ID. See Section 3.2 for rules governing task scheduling and state transitions.
A task has a base priority and a current priority for controlling the order of task execution. In this specification, the words “task priority” refer to the task’s current priority.
When the task is activated, the base priority is set to the task’s initial priority as definedwhen the task is created. If mutexes are not used, the current priority and the base priority are always equal. Therefore, the current priority of a task is set to its initial priority when the task is activated. For more information about how mutexes change thecurrent priority, see Section 4.5.1.
Activation requests for a task are queued. In other words, if a task has already been
activated and an activation request is made for the task, the new request is recorded.
When the task terminates under this situation, the task will be automatically activatedagain. However, activation requests will not be queued when the service call that activates a task with the specified start code (sta_tsk) is used. A task includes an activation request count to realize the activation request queuing. This count is cleared to 0
when the task is created.
When a task is activated, its extended information (exinf) is passed as a parameter.
However, when a task is activated by the service call with a start code (sta_tsk), thespecified start code is passed through the parameter instead of the extended information.
When a task terminates, the kernel does not release resources that the task acquired
such as semaphore resources and memory blocks. However, the kernel unlocks
mutexes acquired by the task. The application program is responsible for releasing
resources acquired by the task when the task terminates.
The following actions must be taken when creating, activating, terminating, and deleting a task. When a task is created, the activation request count is cleared, the task’s
exception handling routine is set to undefined (see Section 4.3), and the task’s processor time limit is set to undefined (see Section 4.7.4). When a task is activated, thetask’s base priority and current priority are initialized, the task’s wakeup request countis cleared (see Section 4.2), the task’s suspension count is cleared (see Section 4.2), thetask’s pending exception code is cleared (see Section 4.3), and the task’s exception
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handling is disabled (see Section 4.3). When a task is terminated, all mutexes locked
by the task are unlocked (see Section 4.5.1) and the processor time limit is set to undefined (see Section 4.7.4). When a task is deleted, the task’s stack space is released if
the stack space was allocated by the kernel when the task was created.
The format to write a task in the C language is shown below:
void task ( VP_INT exinf ){/* Body of the task */ext_tsk ( ) ;}The behavior of a task returning from its main routine is identical to invoking ext_tsk,
i.e. the task terminates. exd_tsk deletes the invoking task in addition to terminating
the task.
The following kernel configuration constant is defined for use with task management
functions:
TMAX_ACTCNT

Maximum activation request count

The following data type packets are defined for creating and referencing tasks:
typedef struct t_ctsk {ATRtskatr ;/* Task attribute */VP_INT
exinf ;/* Task extended information */FPtask ;/* Task start address */PRI
itskpri ;/* Task initial priority */SIZEstksz ;/* Task stack size (in bytes) */VP
stk ;/* Base address of task stack space *//* Other implementation specific fields may be added. */} T_CTSK ;typedef struct t_rtsk {STAT
tskstat ;PRI
tskpri ;PRI
tskbpri ;STAT
tskwait ;ID
wobjid ;/* Task state *//* Task current priority *//* Task base priority *//* Reason for waiting *//* Object ID number for which the task iswaiting */TMO
lefttmo ;/* Remaining time until timeout */UINT
actcnt ;/* Activation request count */UINT
wupcnt ; /* Wakeup request count */UINTsuscnt ;/* Suspension count *//* Other implementation specific fields may be added. */} T_RTSK ;typedef struct t_rtst {STAT
tskstat ;/* Task state */STAT
tskwait ; /* Reason for waiting *//* Other implementation specific fields may be added. */} T_RTST ;80

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The following represents the function codes for the task management service calls:
TFN_CRE_TSK
TFN_ACRE_TSK
TFN_DEL_TSK
TFN_ACT_TSK
TFN_IACT_TSK
TFN_CAN_ACT
TFN_STA_TSK
TFN_EXT_TSK
TFN_EXD_TSK
TFN_TER_TSK
TFN_CHG_PRI
TFN_GET_PRI
TFN_REF_TSK
TFN_REF_TST

–0x05
–0xc1
–0x06
–0x07
–0x71
–0x08
–0x09
–0x0a
–0x0b
–0x0c
–0x0d
–0x0e
–0x0f
–0x10

Function code of cre_tsk
Function code of acre_tsk
Function code of del_tsk
Function code of act_tsk
Function code of iact_tsk
Function code of can_act
Function code of sta_tsk
Function code of ext_tsk
Function code of exd_tsk
Function code of ter_tsk
Function code of chg_pri
Function code of get_pri
Function code of ref_tsk
Function code of ref_tst[Standard Profile]
The Standard Profile requires support for task management functions except for
dynamic creation and deletion of a task (cre_tsk, acre_tsk, del_tsk), activation of atask with the specified start code ( sta_tsk ), termination and deletion of a task
(exd_tsk), and reference of a task state (ref_tsk, ref_tst).
The Standard Profile requires support for an activation request count of one or more.
Therefore, TMAX_ACTCNT must be at least 1.
[Supplemental Information]
The contexts and states under which tasks execute are summarized as follows:
TMAX_ACTCNT must be 0 if activation request queuing of a task is not supported.
• Tasks execute in their own independent contexts (see Section 3.5.1). The contexts inwhich tasks execute are classified as task contexts (see Section 3.5.2).
• Tasks execute at lower precedence than the dispatcher (see Section 3.5.3).
• After tasks start, the system is both in the CPU unlocked state and in the dispatchingenabled state. When tasks exit, the system must be both in the CPU unlocked stateand in the dispatching enabled state (see Sections 3.5.4 and 3.5.5).
TMAX_ACTCNT must be 0 if activation request queuing of a task is not supported.
[Differences from the µITRON3.0 Specification]
Functions that directly operate on tasks and that have no relation with waiting states areclassified as task management functions. Functions that change task precedence(rot_rdq), reference the ID of the task in the RUNNING state (get_tid), and enable ordisable task dispatching (ena_dsp, dis_dsp) are now classified as system state management functions. The function releasing a task from a waiting state (rel_wai) is now

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classified as a task dependent synchronization function.
Service calls for requesting task activation and canceling the activation requests havebeen added (act_tsk, can_tsk). The service call for starting a task with the specified
start code (sta_tsk) has not been removed to maintain backward compatibility withµITRON3.0; however, this service call is not required in the Standard Profile.
The concept of task base priorities is introduced due to the addition of mutexes. If
mutexes are not used, the behavior is the same as in µITRON3.0 because the base priority is always equal to the current priority.
Returning from a task’s main routine now terminates the task.

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CRE_TSK
cre_tsk
acre_tsk

Ver. 4.00.00[S]

Create Task (Static API)
Create Task
Create Task (ID Number Automatic Assignment)[Static API]
CRE_TSK ( ID tskid, { ATR tskatr, VP_INT exinf, FP task,
PRI itskpri, SIZE stksz, VP stk } ) ;[C Language API]ER ercd = cre_tsk ( ID tskid, T_CTSK *pk_ctsk ) ;ER_ID tskid = acre_tsk ( T_CTSK *pk_ctsk ) ;[Parameter]ID
T_CTSK *tskid
pk_ctskID number of the task to be created (except
acre_tsk)
Pointer to the packet containing the task creation
information (In CRE_TSK, the contents must be
directly specified.)

pk_ctsk includes (T_CTSK type)
ATR
tskatrTask attribute
VP_INT
exinf
Task extend information
FP
task
Task start address
PRI
itskpri
Task initial priority
SIZE
stksz
Task stack size (in bytes)
VP
stk
Base address of task stack space(Other implementation specific information may be added.)[Return Parameter]
cre_tsk:ER

ercd

E_OK for normal completion or error code

acre_tsk:
ER_ID

tskid

ID number (positive value) of the created task orerror code

[Error Code]
E_ID
E_NOID
E_NOMEM
E_RSATR

Invalid ID number (tskid is invalid or unusable; only
cre_tsk)No ID number available (there is no task ID assignable; only
acre_tsk)
Insufficient memory (stack space or other memory cannot beallocated)
Reserved attribute (tskatr is invalid or unusable)
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µITRON4.0 Specification
E_PAR
E_OBJ

Ver. 4.00.00

Parameter error (pk_ctsk, task, itskpri, stksz, or stk isinvalid)Object state error (task is already registered; only cre_tsk)[Functional Description]
These service calls create a task with an ID number specified by tskid based on theinformation contained in the packet pointed to by pk_ctsk. The task is moved fromthe NON-EXISTENT state to either the DORMANT state or the READY state. In
addition, the actions that must be taken at task creation time are performed. tskatr is
the attribute of the task. exinf is the extended information passed as a parameter to thetask when the task is started. task is the start address of the task. itskpri is the initialvalue of the task’s base priority when the task is activated. stksz is the stack size inbytes of the task. stk is the base address of the task’s stack space.
In CRE_TSK, tskid is an integer parameter with automatic assignment. tskatr is a
preprocessor constant expression.
acre_tsk assigns a task ID from the pool of unassigned task IDs and returns theassigned task ID.
tskatr can be specified as ((TA_HLNG || TA_ASM) | [TA_ACT]). If TA_HLNG(= 0x00) is specified, the task is started through the C language interface. If TA_ASM(= 0x01) is specified, the task is started through the assembler language interface.
After the creation, the task is moved to the READY state if TA_ACT (= 0x02) is specified, and is moved to the DORMANT state otherwise.
The memory area defined by the base address stk and the size stksz is used by thetask for its stack space during execution. If stk is NULL (= 0), the kernel allocates amemory area with size stksz for use as the task’s stack space.
[Standard Profile]
The Standard Profile does not require support for when TA_ASM is specified intskatr. It also does not require support for when other values than NULL are specified in stk.
[Supplemental Information]
Several processing units besides the task, such as service calls invoked by the task andinterrupt handlers started during the task’s execution, may use the task’s stack spacedepending on the implementation. The implementation’s documentation, such as the
product manuals, should describe how to calculate the necessary stack size.
The base address of the task stack’s space indicates the lowest address of the memoryarea used as the task stack space. Therefore, in general, the initial value of the task’s
stack pointer does not correspond to the base address of the stack.
A task cannot specify its own task ID in tskid. If a task does specify its own task ID,
cre_tsk returns an E_OBJ error because the task is already registered.

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Ver. 4.00.00[Differences from the µITRON3.0 Specification]
The base address of the task’s stack space, stk, has been added. stk should be set to
NULL if compatibility is required with µITRON3.0.
The order of tskatr and exinf in the task’s creation information packet has been
exchanged. The data type of exinf has been changed from VP to VP_INT. The data
type of stksz has been changed from INT to SIZE.
The ability to move a task directly to the READY state has been added through the useof the added task attribute TA_ACT. This is useful for the case when a task is staticallycreated. The task attributes indicating the task uses co-processors have been removed.
When necessary, such attributes can be added as implementation-specific.
acre_tsk has been newly added.

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del_tskVer. 4.00.00

Delete Task

[C Language API]ER ercd = del_tsk ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_OBJ

ID number of the task to be deleted
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (specified task is not in the DORMANT
state)[Functional Description]
This service call deletes the task specified by tskid. The deleted task is moved fromthe DORMANT state to the NON-EXISTENT state and the actions that must be taken
at task deletion time are performed.
If the task is not in the DORMANT state, an E_OBJ error is returned. However, if thetask is not registered, an E_NOEXS error is returned.
[Supplemental Information]
A task cannot specify its own task ID in tskid. If a task does specify its own task ID,
del_tsk returns an E_OBJ error because the task is not in the DORMANT state.
exd_tsk can be used by a task to terminate and delete itself.

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act_tskiact_tsk

Ver. 4.00.00[S]

Activate Task

[S]

[C Language API]ER ercd = act_tsk ( ID tskid ) ;ER ercd = iact_tsk ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXSE_QOVR

ID number of the task to be activated
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Queue overflow (overflow of activate request queuing count)[Functional Description]
These service calls activate the task specified by tskid. The task is moved from the
DORMANT state to the READY state and the actions that must be taken at task activation time are performed. The extended information of the task is passed to the task as aparameter.
If the task is not in the DORMANT state, the activation request for the task is queued.
(However, if the task in the NON-EXISTENT state, an E_NOEXS error is returned.)
Specifically, the activation request count is incremented by 1. If the count then exceeds
the maximum possible count, an E_QOVR error is returned.
If the service call is invoked from non-task contexts and has its execution delayed, an
E_QOVR error may not be returned.
If tskid is TSK_SELF (= 0), the invoking task is specified. If TSK_SELF is specified when this service call is invoked from non-task contexts, an E_ID error isreturned.
[Supplemental Information]
The Standard Profile requires the maximum activation request count to be at least 1.
This implies that a kernel that is compatible with the Standard Profile may not always
return an E_QOVR error even if these service calls are invoked on a task with queued
activation requests.
[Differences from the µITRON3.0 Specification]
These service calls have been newly added.

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can_act

Ver. 4.00.00

Cancel Task Activation Requests[S][C Language API]ER_UINT actcnt = can_act ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]
ER_UINT actcnt[Error Code]
E_ID
E_NOEXS

ID number of the task for cancelling activation
requests
Activation request count (positive value or 0) or
error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)[Functional Description]
This service call cancels all queued activation requests for the task specified by tskid
and returns the cancelled request count for the task. Specifically, the activation request
count for the task is cleared to 0. The value returned is the count before it was cleared.
If tskid is TSK_SELF (= 0), the invoking task is specified.
[Supplemental Information]
This service call may specify a task in the DORMANT state. In this case, the service
call returns a count of 0 because activation requests are not queued for the task.
This service call can be used to check if a task completes a process within a cycle correctly when the task is activated cyclically. Specifically, can_act should be invokedwhen the task completes the process. A return value of 1 or more from can_act indicates that the next activation is requested before the task completes the process in theprevious cycle. The task can take measures for this case.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

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sta_tskVer. 4.00.00

Activate Task (with a Start Code)[C Language API]ER ercd = sta_tsk ( ID tskid, VP_INT stacd ) ;[Parameter]ID
VP_INT

tskid
stacd

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_OBJ

ID number of the task to be activatedStart code of the task
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (specified task is not in the DORMANT
state)[Functional Description]
This service call activates the task specified by tskid. The task is moved from the
DORMANT state to the READY state and the actions that must be taken at task activation time are performed. The start code, stacd, is passed to the task as a parameter.
If the task is not in the DORMANT state, the service call does not queue a request for
activation and returns an E_OBJ error. If the task is in the NON-EXISTENT state, it
returns an E_NOEXS error.
[Supplemental Information]
A task cannot specify its own task ID in tskid. If a task does specify its own task ID,
sta_tsk returns an E_OBJ error because the task is not in the DORMANT state.
[Differences from the µITRON3.0 Specification]
The data type for stacd has been changed from INT to VP_INT.

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ext_tskVer. 4.00.00

Terminate Invoking Task

[S]

[C Language API]
void ext_tsk ( ) ;[Parameter]
None[Return Parameter]This service call does not return.
[Functional Description]
This service call terminates the invoking task. The invoking task is moved from the
RUNNING state to the DORMANT state and the actions that must be taken at task termination time are performed.
If activation requests are queued, that is, if the activation request count for the invoking
task is 1 or more, the count is decremented by 1 and the task is moved to the READY
state. In this case, the actions that must be taken at task activation time are performed.
The extended information of the task is passed to the task as a parameter.
This service call never returns; therefore, no error code is returned even if an error isencountered in the service call. The behavior of the service call when an error is
detected is implementation-defined.
[Supplemental Information]
When activation requests are queued for the invoking task, this service call will reactivate the task after it has been terminated. This implies that all mutexes locked by thetask are unlocked and the processing time limit is set to undefined. In addition the basepriority, the current priority, the wakeup request count, the suspension count, the pending exception code, and the task exception handling state are all reset to their initial values. The task has the lowest precedence among all tasks with the same priority in the
READY state.
When an error is detected in the service call, the information regarding the error can belogged.
The behavior of a task returning from its main routine is identical to invoking ext_tsk.
[Differences from the µITRON3.0 Specification]
Tasks that invoke ext_tsk may be reactivated due to the addition of the activation
request count.

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exd_tskVer. 4.00.00

Terminate and Delete Invoking Task

[C Language API]
void exd_tsk ( ) ;[Parameter]
None[Return Parameter]This service call does not return.
[Functional Description]
This service call terminates and deletes the invoking task. The task is moved from the
RUNNING state to the NON-EXISTENT state and the actions that must be taken attask termination and deletion time are performed.
This service call never returns; therefore, no error code is returned even if an error isencountered in the service call. The behavior of the service call when an error is
detected is implementation-defined.
[Supplemental Information]
This service call terminates and deletes the invoking task even if activation requests arequeued for the invoking task. The activation request count has no meaning when thetask is in the NON-EXISTENT state.
When an error is detected in the service call, the information regarding the error can belogged.

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ter_tskVer. 4.00.00[S]

Terminate Task

[C Language API]ER ercd = ter_tsk ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_ILUSE
E_OBJ

ID number of the task to be terminated
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Illegal service call use (specified task is an invoking task)
Object state error (specified task is in the DORMANT state)[Functional Description]
This service call terminates the task specified by tskid. The task is moved to the
DORMANT state and the actions that must be taken at task termination time are performed.
If activate requests are queued, that is, if the activation request count for the specified
task is 1 or more, the count is decremented by 1 and the task is moved to the READY
state. In this case, the actions that must be taken at task activation time are performed.
The extended information of the task is passed to the task as a parameter.
If the task is in the DORMANT state, an E_OBJ error is returned. A task cannot terminate itself with this service call. If a task specifies its own task ID in tskid, an
E_ILUSE error is returned.
[Supplemental Information]
This service call forces the specified task to terminate even if the task is in the blocked
state. When the task is waiting in a wait queue, the task is removed from the queue. In
this case, some other tasks that are in the wait queue may need to be released fromwaiting. See the functional descriptions of snd_mbf and get_mpl.
When activation requests are queued for the specified task, this service call will reactivate the task after it has been terminated. This implies that all mutexes locked by thetask are unlocked and the processing time limit is set to undefined. In addition the basepriority, the current priority, the wakeup request count, the suspension count, the pending exception code, and the task exception handling state are all reset to their initial values. The task has the lowest precedence among all tasks with the same priority in the
READY state.

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Ver. 4.00.00[Differences from the µITRON3.0 Specification]
The main error code when the invoking task is specified has been changed from
E_OBJ to E_ILUSE.
This service call may reactivate the specified task due to the addition of the activation
request count.

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chg_priVer. 4.00.00[S]

Change Task Priority[C Language API]ER ercd = chg_pri ( ID tskid, PRI tskpri ) ;[Parameter]
ID

tskid

PRI

tskpri[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_ILUSE
E_OBJ

ID number of the task whose priority is to bechangedNew base priority of the task
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Parameter error (tskpri is invalid)
Illegal service call use (priority ceiling violation)
Object state error (specified task is in the DORMANT state)[Functional Description]
This service call changes the base priority of the task specified by tskid to the priority
value specified by tskpri. The current priority can also be changed.
If tskid is TSK_SELF (= 0), the priority of the invoking task is changed. If tskpri is
TPRI_INI (= 0), the base priority is changed to the task’s initial priority.
If the invocation of this service call results in equal base and current priorities, which isalways the case if mutexes are not used, the following actions are performed. If thetask is runnable, the task’s precedence is changed to reflect the new priority. The task
will have the lowest precedence among tasks with the same priority. If the task is waiting in a wait queue, the task’s position in the queue is changed to reflect the new priority. The task will be placed last among tasks with the same priority.
If the task locked mutexes with the TA_CEILING attribute and the new base priority,
tskpri , is higher than one of the ceilings of the mutexes, an E_ILUSE error isreturned.
[Supplemental Information]
When the task is waiting in a wait queue, this service call may change the task’s orderin the wait queue. In this case, some other tasks that are in the wait queue may need tobe released from waiting. See the functional descriptions of snd_mbf and get_mpl.
If the specified task is waiting for a mutex with the TA_INHERIT attribute, transitive
priority inheritance needs to be applied as the result of changing the base priority of the
task.
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Ver. 4.00.00

When mutexes are not used and when this service call is invoked with the invoking task
in tskid and its base priority in tskpri, the task will have the lowest precedence among
all tasks with the same priority. Therefore, this service call can be used to yield theexecution privilege to another task.
[Differences from the µITRON3.0 Specification]
chg_pri now changes the base priority of a task due to the addition of mutexes.
Allowing tskpri to be set to TPRI_INI is now standard.

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µITRON4.0 Specification

get_priVer. 4.00.00[S]

Reference Task Priority[C Language API]ER ercd = get_pri ( ID tskid, PRI *p_tskpri ) ;[Parameter]
ID

tskid

[Return Parameter]
ER
ercd
PRI
tskpri[Error Code]
E_ID
E_NOEXS
E_OBJ

ID number of the task to reference
E_OK for normal completion or error code
Current priority of specified task

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (specified task is in the DORMANT state)[Functional Description]
This service call returns the current priority of the task specified by tskid throughtskpri.
If tskid is TSK_SELF (= 0), the current priority of the invoking task is returned.
[Supplemental Information]
get_pri refers to the task’s current priority while chg_pri changes the task’s base priority.
[Differences from the µITRON3.0 Specification]
This service call has been newly added, because a method is required to obtain an
invoking task’s priority with minimal overhead when the priority of a message to besent should be set to the task’s priority.
[Rationale]
The priority is returned through tskpri as opposed to a return value in order for theservice call to be consistent with other similar service calls (get_yyy) and in order toallow an implementation-specific extension to use negative values for priorities.

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µITRON4.0 Specification

ref_tskVer. 4.00.00

Reference Task State[C Language API]ER ercd = ref_tsk ( ID tskid, T_RTSK *pk_rtsk ) ;[Parameter]ID
T_RTSK *tskid
pk_rtsk[Return Parameter]ER
ercd

ID number of the task to be referenced
Pointer to the packet returning the task state
E_OK for normal completion or error code

pk_rtsk includes (T_RTSK type)
STAT
tskstatTask state
PRI
tskpri
Task current priority
PRI
tskbpri
Task base priority
STAT
tskwait
Reason for waitingID
wobjidObject ID number for which the task is waiting
TMO
lefttmoRemaining time until timeout
UINT
actcntActivation request countUINT
wupcntWakeup request countUINTsuscntSuspension count(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Parameter error (pk_rtsk is invalid)[Functional Description]
This service call references the state of the task specified by tskid. The state of thetask is returned through the packet pointed to by pk_rtsk. If the specified task is in
the NON-EXISTENT state, an E_NOEXS error is returned.
One of the following codes is returned through tskstat to indicate the state of the task:
TTS_RUNTTS_RDY
TTS_WAITTS_SUSTTS_WASTTS_DMT

0x01
0x02
0x04
0x08
0x0c
0x10

RUNNING state
READY state
WAITING state
SUSPENDED state
WAITING-SUSPENDED state
DORMANT state

If the task is not in the DORMANT state, the current priority is returned throughtskpri and the base priority is returned through tskbpri. If the task is in the DORMANT state, the values returned through tskpri and tskbpri are implementa97

µITRON4.0 Specification

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tion-dependent.
If the task is in the WAITING state, including the WAITING-SUSPENDED state, oneof the following codes is returned through tskwait to indicate the reason of the task’s
waiting. If the task is not in the WAITING state, the value returned through tskwait is
implementation-dependent.
TTW_SLPTTW_DLY
TTW_SEM
TTW_FLG
TTW_SDTQ
TTW_RDTQ
TTW_MBX
TTW_MTX
TTW_SMBF
TTW_RMBF
TTW_CAL
TTW_ACP
TTW_RDVTTW_MPF
TTW_MPL

0x00010x00020x00040x00080x00100x00200x00400x00800x01000x02000x04000x08000x10000x20000x4000Sleeping state
Delayed state
Waiting state for a semaphore resource
Waiting state for an eventflag
Sending waiting state for a data queue
Receiving waiting state for a data queue
Receiving waiting state for a mailbox
Waiting state for a mutex
Sending waiting state for a message buffer
Receiving waiting state for a message buffer
Calling waiting state for a rendezvous
Accepting waiting state for a rendezvous
Terminating waiting state for a rendezvous
Waiting state for a fixed-sized memory block
Waiting state for a variable-sized memory block

If the task is in the WAITING state, including the WAITING-SUSPENDED state, theID of the object the task is waiting for is returned through wobjid. This does not apply
when the task is in the sleeping state, the delayed state, or the termination waiting state
for a rendezvous. In these states, the value returned through wobjid is implementation-dependent. If the task is not in the WAITING state, the value returned throughwobjid is also implementation-dependent.
When the task is in the WAITING state, including the WAITING-SUSPENDED state,
but not in the delayed state, the amount of time remaining for the task to timeout isreturned through the parameter lefttmo. The value of lefttmo is calculated by subtracting the current time from the time at which the task will timeout. The value
returned through lefttmo, however, must be less than or equal to the actual amount oftime until timeout. This means that if the timeout happens at the next time tick, 0 is
returned through lefttmo. If the task is in the WAITING state forever (that is, waiting
without a timeout), TMO_FEVR is returned through lefttmo. If the task is not in the
WAITING state or is in the delayed state, the value returned through lefttmo is implementation-dependent.
The service call returns the task’s activation request count through actcnt.
If the task is not in the DORMANT state, the wakeup request count and suspension
count are returned through wupcnt and suscnt respectively. If the task is in the
DORMANT state, the values returned through wupcnt and suscnt are implementa-

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tion-dependent.
If tskid is TSK_SELF (= 0), the state of the invoking task is referenced.
[Differences from the µITRON3.0 Specification]
Referencing many pieces of information in the µITRON3.0 specification was implementation-dependent, but is now considered standard. The return parameter wid has
been changed to wobjid. In addition the following items have been added: task basepriority (tskbpri), remaining time until timeout (lefttmo), and activation request
count (actcnt). The extended information has been removed from the list.
The order of tskstat and tskpri in pk_rtsk has been exchanged. The data type fortskstat has been changed from UINT to STAT. The order of parameters and of
return parameters has been changed.
The return values are now implementation-dependent under cases where parameters
have no meaning for specific tasks states. For example, if the task is in the DORMANT state, the value returned through tskpri is implementation-dependent.
The values returned through tskwait have been reassigned.
[Rationale]
If the task is in the delayed state, the value returned through lefttmo is implementdependent because the delayed time data type used by dly_tsk is RELTIM (unsigned
integer) and it cannot be always returned through lefttmo which is of TMO (signed
integer).

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µITRON4.0 Specification

ref_tstVer. 4.00.00

Reference Task State (Simplified Version)[C Language API]ER ercd = ref_tst ( ID tskid, T_RTST *pk_rtst ) ;[Parameter]ID
T_RTST *tskid
pk_rtst[Return Parameter]ER
ercd

ID number of the task to be referenced
Pointer to the packet returning the task state
E_OK for normal completion or error code

pk_rtst includes (T_RTST type)
STAT
tskstatTask stateSTAT
tskwait
Reason for waiting(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Parameter error (pk_rtst is invalid)[Functional Description]
This service call references the minimum task state information for the task specified
by tskid. The state of the task is returned through the packet pointed to by pk_rtst.
This service call is a simplified version of ref_tsk. The same values returned by
ref_tsk through tskstat and tskwait apply to ref_tst as well.
If tskid is TSK_SELF (= 0), the state of the invoking task is referenced.
[Rationale]
A task’s information can be referenced with ref_tsk. However, if only minimum
information is required, an overhead on data space is incurred for the rest of the possible information. A new service call, ref_tst, has been added in order to extract just theminimum task information.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

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4.2 Task Dependent Synchronization Functions
Task dependent synchronization functions provide direct control of task states to synchronize tasks. Task dependent synchronization functions include the ability to put atask to the sleeping state, to wakeup a task from the sleeping state, to cancel wakeup
requests, to forcibly release a task from waiting, to suspend a task, to resume a task
from the SUSPENDED state, and to delay the execution of the invoking task.
Wakeup requests for a task are queued. In other words, if a task is not in the sleeping
state and a wakeup request is made for the task, the new request is recorded. When thetask enters the sleeping state under this situation, the task will not be put in the sleeping
state. A task includes a wakeup request count to realize the wakeup request queuing.
This count is cleared to 0 when the task is activated.
Suspension requests for a task are nested. In other words, if a task has already been in
the SUSPENDED state, including WAITING-SUSPENDED state, and an attempt ismade to put the task in the SUSPENDED state again, the new request is recorded.
When an attempt is made to resume the task from SUSPENDED state under this situation, the task will not be resumed. A task includes a suspension count to realize thesuspension request nesting. This count is cleared to 0 when the task is activated.
The following kernel configuration constants are defined for use with task dependent
synchronization functions:
TMAX_WUPCNTTMAX_SUSCNT

Maximum wakeup request countMaximum suspension count

The following represents the function codes for the task dependent synchronization
service calls:
TFN_SLP_TSK
TFN_TSLP_TSK
TFN_WUP_TSK
TFN_IWUP_TSK
TFN_CAN_WUP
TFN_REL_WAI
TFN_IREL_WAI
TFN_SUS_TSK
TFN_RSM_TSK
TFN_FRSM_TSK
TFN_DLY_TSK

–0x11
–0x12
–0x13
–0x72
–0x14
–0x15
–0x73
–0x16
–0x17
–0x18
–0x19

Function code of slp_tsk
Function code of tslp_tsk
Function code of wup_tsk
Function code of iwup_tsk
Function code of can_wup
Function code of rel_wai
Function code of irel_wai
Function code of sus_tsk
Function code of rsm_tsk
Function code of frsm_tsk
Function code of dly_tsk[Standard Profile]
The Standard Profile requires support for task dependent synchronization functions.
The Standard Profile requires support for a wakeup request count of one or more. It
also requires support for the SUSPENDED state for a task. Therefore, each of101

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TMAX_WUPCNT and TMAX_SUSCNT must be at least 1.
[Supplemental Information]
TMAX_WUPCNT is undefined if the sleeping state for a task is not supported and is 0
if the wakeup request queuing is not supported. TMAX_SUSCNT is undefined if the
SUSPENDED state for a task is not supported, thus, TMAX_SUSCNT is never 0.
[Differences from the µITRON3.0 Specification]
The functions for releasing a task from waiting, rel_wai, and for delaying the invoking
task’s execution, dly_tsk, are now classified as task dependent synchronization functions.

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µITRON4.0 Specification

slp_tsktslp_tsk

Ver. 4.00.00

Put Task to Sleep[S]

Put Task to Sleep (with Timeout)[S][C Language API]ER ercd = slp_tsk ( ) ;ER ercd = tslp_tsk ( TMO tmout ) ;[Parameter]
TMO

tmout

[Return Parameter]ER
ercd[Error Code]
E_PAR
E_RLWAIE_TMOUTSpecified timeout (only for tslp_tsk)
E_OK for normal completion or error code

Parameter error (tmout is invalid; only for tslp_tsk)
Forced release from waiting (accept rel_wai while waiting)
Polling failure or timeout (only tslp_tsk)[Functional Description]
These service calls move the invoking task to the sleeping state. However, if wakeup
requests are queued, that is, if the wakeup request count for the invoking task is 1 or
more, the count is decremented by 1 and the invoking task continues execution.
tslp_tsk has the same functionality as slp_tsk with an additional timeout feature.
tmout can be set to a positive number indicating a timeout duration or it can be set to
TMO_POL (= 0) or TMO_FEVR (= –1).
[Supplemental Information]
These service calls do not move the invoking task to the WAITING state if wakeup
requests for the invoking task are queued. Thus the precedence of the invoking task is
not changed.
No polling service call is provided for slp_tsk. If a similar feature is necessary, it canbe implemented using can_wup.

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µITRON4.0 Specification

wup_tskiwup_tsk

Ver. 4.00.00[S]

Wakeup Task

[S]

[C Language API]ER ercd = wup_tsk ( ID tskid ) ;ER ercd = iwup_tsk ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_OBJ
E_QOVR

ID number of the task to be woken up
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (specified task is in the DORMANT state)
Queue overflow (overflow of wakeup request count)[Functional Description]
These service calls wake up the task specified by tskid from sleeping. The service callthat placed the task in the WAITING state will return E_OK to the task.
If the task is not in the sleeping state, the wakeup request for the task is queued. (However, if the task is in the NON-EXISTENT state, an E_NOEXS error is returned and if
the task is in the DORMANT state, an E_OBJ error is returned.) Specifically, thewakeup request count is incremented by 1. If the count then exceeds the maximum
possible count, an E_QOVR error is returned.
If this service call is invoked from non-task contexts and has its execution delayed, an
E_OBJ error and an E_QOVR error may not be returned.
If tskid is TSK_SELF (= 0), the invoking task is specified. If TSK_SELF is specified
when this service call is invoked from non-task contexts, an E_ID error is returned.
[Supplemental Information]
The Standard Profile requires the maximum wakeup request count to be at least 1. Thisimplies that a kernel that is compatible with the Standard Profile may not always return
an E_QOVR error even if these service calls are invoked on a task with queued
wakeup requests.
[Differences from the µITRON3.0 Specification]
The invoking task can now be specified in this service call for the consistency with
act_tsk.

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µITRON4.0 Specification

can_wupVer. 4.00.00

Cancel Task Wakeup Requests[S][C Language API]ER_UINT wupcnt = can_wup ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]
ER_UINT wupcnt[Error Code]
E_ID
E_NOEXS
E_OBJ

ID number of the task for cancelling wakeup
requests
Wakeup request count (positive value or 0) or error
code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (specified task is in the DORMANT state)[Functional Description]
This service call cancels all queued wakeup requests for the task specified by tskid
and returns the cancelled request count for the task. Specifically, the wakeup request
count for the task is cleared to 0. The value returned is the count before it was cleared.
If tskid is TSK_SELF (= 0), the invoking task is specified.
[Supplemental Information]
This service call can be used to check if a task completes a process within a cycle correctly when the task is woken up cyclically. Specifically, can_wup should be invokedwhen the task completes the process. A return value of 1 or more from can_wup indicates that the next wakeup request is done before the task completes the process in theprevious cycle. The task can take measures for this case.
[Differences from the µITRON3.0 Specification]
The wakeup request count (wupcnt) is now the return value of this service call.

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µITRON4.0 Specification

rel_wai
irel_waiVer. 4.00.00

Release Task from Waiting

[S]
[S]

[C Language API]ER ercd = rel_wai ( ID tskid ) ;ER ercd = irel_wai ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_OBJ

ID number of the task to be released from waiting
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (specified task is in the DORMANT state)[Functional Description]
These service calls forcibly release the task specified by tskid from waiting. Specifically, if the task is in the WAITING state, it is moved to the READY state. If the task isin the WAITNG-SUSPENDED state, it is moved to the SUSPEDED state. When thetask is released from waiting by these service calls, the service call that placed the task
in the WAITING state will return an E_RLWAI error to the task.
If the task is not in the WAITING state, including the WAITING-SUSPENDED state,an E_OBJ error is returned. However, if the task is in the NON-EXISTENT state, an
E_NOEXS error code is returned. If this service call is invoked from non-task contexts and has its execution delayed, an E_OBJ error may not be returned.
[Supplemental Information]
A task cannot specify its own task ID in tskid. If a task does specify its own task ID,
these service calls return an E_OBJ error because the task is not in the WAITING
state.
These service calls do not cause a task in the SUSPENDED state to resume.
frsm_tsk (or rsm_tsk) should be used to forcibly resume a suspended task.
If the task is waiting in a wait queue, the task is removed from the queue. In this case,some other tasks that are in the wait queue may need to be released from waiting. See
the functional descriptions of snd_mbf and get_mpl.
The following describes the differences between rel_wai and wup_tsk:• rel_wai releases a task from any waiting state, while wup_tsk only releases a task
from the sleeping state.
• To the task in the sleeping state, a success (E_OK) is returned when the task is106

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released from sleeping with slp_tsk, while an error (E_RLWAI) is returned when
the task is forcibly released from waiting with rel_wai.
• wup_tsk will increment the wakeup request count if the task is not in the sleeping
state. On the other hand, rel_wai will return an E_OBJ error if the task is not waiting.

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µITRON4.0 Specification

sus_tskVer. 4.00.00[S]

Suspend Task

[C Language API]ER ercd = sus_tsk ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_CTX
E_NOEXS
E_OBJ
E_QOVR

ID number of the task to be suspended
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Context error (the invoking task is specified while under dispatching disabled state; any other context error)
Non-existent object (specified task is not registered)Object state error (specified task is in the DORMANT state)
Queue overflow (overflow of suspension count)[Functional Description]
This service call suspends the task specified by tskid. Specifically, if the task is runnable, it is moved to the SUSPENDED state. If the task is in the WAITING state, it is
moved to the WAITING-SUSPENDED state. In addition, the suspension count isincremented by 1. If the count then exceeds the maximum possible count, an
E_QOVR error is returned.
This service call can be invoked under the dispatching disabled state. However, under
the dispatching disabled state, if this service call is invoked specifying the invoking
task, an E_CTX error is returned.
If tskid is TSK_SELF (= 0), the invoking task is specified.
[Supplemental Information]
This service call may be invoked under the dispatching disabled state even though the
invoking task may be moved to the SUSPENDED state as specified in the parameter.
Therefore this is an exception to the principle stating that “The restriction that behavior
is undefined when service calls that can move the invoking task to the blocked state are
invoked while in the dispatching disabled state applies to a service as a whole.”
The Standard Profile requires the maximum suspension count to be at least 1. Thisimplies that a kernel that is compatible with the Standard Profile may not always return
an E_QOVR error even if this service call is invoked on a task in the SUSPENDED
state.
[Differences from the µITRON3.0 Specification]
The invoking task can now be specified in tskid.
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µITRON4.0 Specification

rsm_tsk
frsm_tsk

Ver. 4.00.00

Resume Suspended Task

[S]

Forcibly Resume Suspended Task

[S]

[C Language API]ER ercd = rsm_tsk ( ID tskid ) ;ER ercd = frsm_tsk ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_OBJ

ID number of the task to be resumed
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (specified task is neither in the SUSPENDED state nor WAITING-SUSPENDED state)[Functional Description]
These service calls release the task specified by tskid from the SUSPENDED state
and allows the task to continue its normal processing. Specifically, the following
actions are performed.
rsm_tsk decrements the suspension count of the task by 1. If the count becomes 0,
the task is moved according to the following: if the task is in the SUSPEDED state, it is
moved to the READY state; if the task is in the WAITING-SUSPENDED state, it is
moved to the WAITING state. If the count remains to be 1 or more, the state of the task
is not changed.
frsm_tsk clears the suspension count to 0 and forcibly moves the task according to
the following: if the task is in the SUSPEDED state, it is moved to the READY state; if
the task is in the WAITING-SUSPENDED state, it is moved to the WAITING state.
If the specified task is neither in the SUSPENDED state nor WAITING-SUSPENDED
state, an E_OBJ error is returned. However, if the task is in the NON-EXISTING
state, an E_NOEXS error is returned.
[Supplemental Information]
A task cannot specify its own task ID in tskid. If a task does specify its own task ID,
these service calls return an E_OBJ error because the task is not in the SUSPENDED
state. When an implementation-specific service call is capable of moving a task to the
SUSPENDED state from non-task contexts or moving the invoking task to the SUSPENDED state under the dispatching disabled state, the invoking task may have thesuspension count of 1 or more. The behavior of rsm_tsk and frsm_tsk in this case is109

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implementation-dependent.
[Differences from the µITRON3.0 Specification]
After a task is moved from the SUSPENDED state to the READY state, the task has
the lowest precedence among all tasks with the same priority in the READY state. See
Section 3.2.1 for more details.

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µITRON4.0 Specification

dly_tskVer. 4.00.00[S]

Delay Task

[C Language API]ER ercd = dly_tsk ( RELTIM dlytim ) ;[Parameter]
RELTIM

dlytim[Return Parameter]ER
ercd[Error Code]
E_PAR
E_RLWAI

Amount of time to delay the invoking task (relativetime)
E_OK for normal completion or error code

Parameter error (dlytim is invalid)
Forced release from waiting (accept rel_wai while waiting)[Functional Description]
This service call delays the execution of the invoking task for the amount of time specified in dlytim. Specifically, the invoking task is set to be released from waiting when
the specified relative time has passed since the invocation of this service call, and thenit is moved to the delayed state. When the task is released from waiting after the relative time expires, the service call completes and returns E_OK.
dlytim is the relative time when the task is released from the delayed state withrespect to the time when the service call is invoked.
[Supplemental Information]
The release of a task from the delayed state depends on the system time. Therefore, thetask is released at the first time tick after the specified time has passed. The system
must guarantee that the release of the task occurs after an elapsed time equal to or
greater than the specified time (see Section 2.1.9). This service call moves the invoking
task to the delayed state even if dlytim is 0.
The delayed state is a kind of the WAITING state and can be forcibly released with
rel_wai. The delayed time includes the time a task spends in the WAITING-SUSPENDED state.
This service call is different from tslp_tsk in that it returns E_OK when the specified
time expires. Also, an invocation of wup_tsk for the task will not release the task
from the delayed state. Only ter_tsk and rel_wai can release the task from thedelayed state before the time expires.
[Differences from the µITRON3.0 Specification]
The data type of dlytim has been changed from DLYTIME to RELTIM.

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4.3 Task Exception Handling Functions
Task exception handling functions provide handling task exceptions within the task’scontext. Task exception handling functions include the ability to define a task exception handling routine, to request a task exception handling, to enable and disable task
exception handling, and to reference the state of a task exception handling.
When a task’s exception handling is requested, the task suspends processing and thetask exception handling routine is started. The handling routine runs within the samecontext as the task itself. Once the task exception handling routine returns, the task
resumes processing. An application can register a task exception handling routine foreach task. A task exception handling routine is not registered when the task is created.
When a task exception handling is requested, the task exception code representing thetype of exception is specified. For each task, the kernel manages the exception code
representing the exceptions that have been requested but have not been processed yet.
This code is referred to as the pending exception code. The pending exception code is
0 if no unprocessed exception request exists. When a task exception handling isrequested for a task that has unprocessed exception requests, the task’s pending exception code is bit-wise ORed with the requested exception code. The pending exception
code is cleared to 0 when the task is activated.
A task can be in either the task exception disabled state or the task exception enabledstate. Moving a task to the task exception disabled state is called “disabling task
exceptions.” Moving a task to the exception enabled state is called “enabling task
exceptions.” Just after a task starts, it is in the task exception disabled state.
The following behavior is implementation-defined. The kernel disables task exceptions when an extended service routine is started and restores the original state when
the routine returns. In addition, if ena_tex is invoked from an extended service callroutine, an E_CTX error is returned because task exceptions should be kept disabledduring the execution of the routine.
A task’s exception handling routine is started when the following four conditions are
met: task exceptions are enabled for the task, the task’s pending exception code is not
0, the task is in the RUNNING state, and non-task contexts or CPU exception handlers
are not being executed. The pending exception code (texptn) and the task’s extended
information (exinf) are passed to the task exception handling routine as parameters.
At this point, task exceptions are disabled and the pending exception code is cleared to0.
When the task exception handling routine returns, the task resumes executing the process that was executing before the routine was started. At this point, the task exceptions are enabled. If the pending exception code is not 0, the task exception handlingroutine is restarted.
The following data type is used for task exception handling functions:
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µITRON4.0 Specification
TEXPTNVer. 4.00.00

Bit pattern for the task exception code (unsigned integer)

The format to write a task exception handling routine in C language is shown below:
void texrtn ( TEXPTN texptn, VP_INT exinf ){/* Body of the task exception handling routine */}The following kernel configuration constant is defined for use with task exception handling functions:
TBIT_TEXPTN

The number of bits in the task exception code (thenumber of bits of TEXPTN type)The following packet data types are defined for defining and referencing task exception
handling routines:
typedef struct t_dtex {ATR
texatr ;/* Task exception handling routine
attribute */FP
texrtn ;/* Task exception handling routine start
address *//* Other implementation specific fields may be added. */} T_DTEX ;typedef struct t_rtex {STAT
texstat ;/* Task exception state */TEXPTN
pndptn ; /* Pending exception code *//* Other implementation specific fields may be added. */} T_RTEX ;The following represents the function codes for the task exception handling service
calls:
TFN_DEF_TEX
TFN_RAS_TEX
TFN_IRAS_TEX
TFN_DIS_TEX
TFN_ENA_TEX
TFN_SNS_TEX
TFN_REF_TEX

–0x1b
–0x1c
–0x74
–0x1d
–0x1e
–0x1f
–0x20

Function code of def_tex
Function code of ras_tex
Function code of iras_tex
Function code of dis_tex
Function code of ena_tex
Function code of sns_tex
Function code of ref_tex[Standard Profile]
The Standard Profile requires support for task exception handling functions except for
dynamic definition of an exception handling routine (def_tex) and reference of a task
exception handling routine state (ref_tex).
The Standard Profile also requires the bit-width for the bit pattern data type to be atleast 16 bits:
TEXPTN

16 bits or more

Therefore, TBIT_TEXPTN must be 16 or more.
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µITRON4.0 Specification

Ver. 4.00.00[Supplemental Information]
The specification does not specify whether a task exception handling routine is started
in the CPU locked state because the behavior of service calls that request task exception handling in the CPU locked state is undefined. On the other hand, a task exception
handling routine must be started if the four task exception handling conditions are met
and even if dispatching is disabled.
The context and states under which task exception handling routines execute are summarized below:• Task exception handling routines execute in the same context as the tasks (see Section 3.5.1). The contexts in which the task exception handling routines execute areclassified as task contexts.
• The start of and the return from the task exception handling routines do not change
the CPU state or the dispatching state (see Sections 3.5.4 and 3.5.5). However, thespecification does not specify whether a task exception handling routine is started in
the CPU locked state.
The circumstances regarding enabling and disabling task exceptions are summarized
below:• When a task is activated, task exceptions for the task are disabled.
• When a task exception handling routine is started, task exceptions are disabled.
Task exceptions are enabled upon the return from the task exception handling routine.
• Invoking dis_tex disables task exceptions and invoking ena_tex enables task
exceptions.
• When the definition of a task exception handling routine is released with def_tex,
task exceptions are disabled.
Task exception handling routines may execute a non-local jump by invoking longjmp
from the standard C library. This is allowed because the exception handling routine
executes within the context of the task. When a non-local jump is used to terminate atask exception handling routine, the kernel does not enable task exceptions because thekernel cannot detect whether the task exception handling routine terminates. The
application may enable the task exceptions by invoking ena_tex. In addition if anapplication executes a non-local jump from the task exception handling routine, theapplication must disable task exceptions in order to maintain integrity of global data
structures (see Rationale below).
A task exception handling routine may be restarted just after it returns. In this case, thestack pointer must be the same as the stack pointer when the routine is started previously. This implies there is no wasted stack space when the task exception handlingroutine is restarted after its completion. If this were not the case, it would be impossible to bound the size of the stack area used by a succession of task exception handling

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routines.
The µITRON4.0 Specification does not provide the functionality to mask a task’s
exception code bit by bit. However, an application could still realize this functionality
through the specified task exception handling functions as described below. An application manages the task exception handling mask for each task. At the beginning of thetask exception handling routine, the application checks if the passed task exception
code is masked or not. If the code is masked, the routine must record that the routine
was started with the exception code and return immediately. To be accurate, the routine
must handle the case where some part of the code is masked and some part of the code
is not masked. Later, when the application changes the task exception handling mask,
the application must check if the exception handling routine was started with a previously masked exception code. If there is a record of a masked exception, the task
exception handling routine is started by the application to handle the exception.
Task exception handling routines are not nested because task exceptions are disabled at
the start of the task exception handling routine. If task exception handling routines arecomplex, especially when the task can enter the WAITING state, there are cases when
the routine may need to be nested because an exception could occur while the exception routine is executing. In cases like this, the exception routine can be nested by
invoking ena_tex within the task exception handling routine. However, some measures must be taken to avoid starting an unlimited number of nested task exception handling routines. An example measure is to mask the currently processing exceptions
with the exception handling mask described above.
If a CPU exception occurs while a task exception handling routine is executing, theCPU exception handler begins executing. Once the CPU exception handler returns, thetask exception handler resumes even if the CPU exception handler requests task exception handling. This is because the task exceptions were disabled when the task exception handling routine started. If the cause of the CPU exception is not removed within
the CPU exception handler, the CPU exception is raised again just after the handler
returns. As a result, the CPU exception will continue forever. This also applies to any
CPU exceptions that occurred while in the task exception disabled state.
In principle the application must avoid cases where a CPU exception occurs while in
the task exception disabled state, when the CPU exception handler requests task exception handling. However, CPU exceptions may not be avoidable due to software and/or
hardware malfunctions. In order to avoid continuous CPU exceptions where CPU
exceptions are unavoidable, the CPU exception handler must reference the task exception handling state and perform special handling when task exceptions are disabled.
Nesting the execution of task exception handling routines using the previously
described method, may also be necessary to shorten the duration task exceptions are
disabled.
In an implementation where different stack spaces are used for the application and the115

µITRON4.0 Specification

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kernel, information stored in the kernel stack space or in the task control block (TCB)
must often be moved to the application stack space in order to support the nesting oftask exception handling routines. For instance, if a task exception handling request
occurs while a task is being preempted, the exception routine will start the next time
when the task enters the READY state. In this case, the task’s states before the preemption, which is stored in the kernel stack space or in the TCB, must be moved to theapplication’s stack space. When the task exception handling routine returns, the taskstates must be restored based on the information stored in the application’s stack space.
[Differences from the µITRON3.0 Specification]
Task exception handling functions have been newly added.
[Rationale]
The µITRON4.0 Specification only includes basic task exception handling functions.
An application can realize more complex exception handling based on the provided
functions when necessary. This allows the application to gain more powerful support
while keeping the kernel compact.
The specification only states that task exception handling routines execute in the samecontext as the task. The description regarding non-local jumps via longjmp is
included in the supplemental information because easy use of longjmp from the task
exception handling routine is dangerous for the reason described in the next paragraph.
A task exception handling routine can safely be terminated forcibly through ext_tsk.
This method is considered to be sufficient for the scope of the Standard Profile.
An easy use of longjmp can result to the following. If a task exception handling routine is started while a global data structure is being operated on and if the task exits thetask exception handling routine with a longjmp, the possibility exists that the data is
corrupted. In such cases, users should be very careful when using of longjmp to exit
the task exception handling routine. Specifically, task exceptions must be disabled
while a global data structure is inconsistent.

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DEF_TEX
def_texVer. 4.00.00

Define Task Exception Handling Routine (Static API)[S]

Define Task Exception Handling Routine[Static API]DEF_TEX ( ID tskid, { ATR texatr, FP texrtn } ) ;[C Language API]ER ercd = def_tex ( ID tskid, T_DTEX *pk_dtex ) ;[Parameter]ID
T_DTEX *tskid
pk_dtex

ID number of the task to be defined
Pointer to the packet containing the task exception
handling routine definition information (inDEF_TEX, the contents must be directly specified.)

pk_dtex includes (T_DTEX type)
ATR
texatrTask exception handling routine attributeFP
texrtn
Task exception handling routine start address(Other implementation specific information may be added.)[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXSE_RSATR
E_PAR

E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Reserved attribute (texatr is invalid or unusable)
Parameter error (pk_dtex or texrtn is invalid)[Functional Description]
This service call defines the task exception handling routine for the task specified bytskid based on the information contained in the packet pointed to by pk_dtex.
texatr is the attribute of the task exception handling routine. texrtn is the start
address of the task exception handling routine.
In DEF_TEX, tskid is an integer parameter without automatic assignment. texatr isa preprocessor constant expression parameter.
If pk_dtex is NULL (= 0), the task exception handling routine currently defined isreleased and the task exception handling routine becomes undefined. At this time, thepending exception code is cleared to 0 and task exception are disabled. When a newtask exception handling routine is defined over top of an old one, the old one is released
and the new one takes its place. Under this condition, the pending exception code is
not cleared and task exceptions are not disabled.

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When tskid is TSK_SELF (= 0), the task exception handling routine is defined forthe invoking task.
texatr can be specified as (TA_HLNG || TA_ASM). If TA_HLNG (= 0x00) is specified, the task exception handling routine is started through the C language interface. If
TA_ASM (= 0x01) is specified, the routine is started through an assembly language
interface.
[Standard Profile]
The Standard Profile does not require support for when TA_ASM is specified in
texatr.
[Supplemental Information]
The task exception handling routine remains effective until def_tex is invoked with
pk_dtex set to NULL or until the task is deleted.
When DEF_TEX is used to define a task exception handling routine for a task, thetask must be created with CRE_TSK appearing before DEF_TEX in the system configuration file.
[Rationale]
When the definition of the task exception handling routine is cancelled, the pending
exception code is cleared and task exceptions are disabled. This is done to keep the
pending exception code to 0 and task exceptions to the disabled state, when the task
exception handling routine is not defined. Once a task exception handling routine
becomes undefined, these conditions are kept because the pending exception code cannot be set and because task exceptions cannot be enabled.

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µITRON4.0 Specification

ras_texiras_texVer. 4.00.00

Raise Task Exception Handling

[S]
[S]

[C Language API]ER ercd = ras_tex ( ID tskid, TEXPTN rasptn ) ;ER ercd = iras_tex ( ID tskid, TEXPTN rasptn ) ;[Parameter]ID
TEXPTN

tskid
rasptn[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_OBJ

ID number of the task requested
Task exception code to be requested
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Parameter error (rasptn is invalid)
Object state error (specified task is in the DORMANT state,task exception handling routine is not defined)[Functional Description]
These service calls request task exception handling for the task specified by tskid.
The task exception code is specified by the bit pattern in rasptn. Specifically, thetask’s pending exception code is bit-wise ORed with the requested exception code.
If tskid is TSK_SELF (= 0), the invoking task is specified. If TSK_SELF is specified when this service call is invoked from non-task contexts, an E_ID error isreturned.
If the task is in the DORMANT state or if the task exception handling routine for thetask is undefined, an E_OBJ error is returned. If the service call is invoked from
non-task contexts and has its execution delayed, an E_OBJ error may not be returned.
If rasptn is 0, an E_PAR error is returned.
[Supplemental Information]
These service calls start the task exception handling routine if all the conditions forstarting the routine are met.
If the task is in the blocked state, these service calls only update the pending exception
code, and do not release the task from waiting nor from the SUSPENDED state. If thetask must be released from the block state, the application can use rel_wai or
frsm_tsk (or rsm_tsk) to do so.
There are many service calls that when invoked from non-task contexts can have their
execution delayed until the system is in a state where dispatching can occur. However,119µITRON4.0 Specification

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this service call must be executed even if the system is in the dispatching disabled state.
For example, if an interrupt handler requests a task exception handling for the task in
the RUNNING state while in the dispatching disabled state, the task exception handling routine must be started just after the return from the interrupt handler. This isuseful for stopping a malfunctioning task running with dispatching disabled byrequesting a task exception handling from an interrupt handler. However, this is notuseful for stopping a task running with the CPU locked or a task running with task
exceptions and dispatching disabled.

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µITRON4.0 Specification

dis_texVer. 4.00.00

Disable Task Exceptions[S][C Language API]ER ercd = dis_tex ( ) ;[Parameter]
None[Return Parameter]ER
ercd[Error Code]
E_OBJ

E_OK for normal completion or error code

Object state error (task exception handling routine is notdefined)[Functional Description]
This service call moves the invoking task to the task exception disabled state. If thetask exception handling routine is not defined for the invoking task, an E_OBJ error isreturned.

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µITRON4.0 Specification

ena_texVer. 4.00.00[S]

Enable Task Exceptions[C Language API]ER ercd = ena_tex ( ) ;[Parameter]
None[Return Parameter]ER
ercd[Error Code]
E_OBJ
E_CTX

E_OK for normal completion or error code

Object state error (the task exception handling routine is notdefined)Context error (invoked from a context not capable of enablingtask exceptions, any other context errors)[Functional Description]
This service call moves the invoking task to the task exception enabled state. If thetask exception handling routine is not defined for the invoking task, an E_OBJ error isreturned.
For an implementation that does not allow task exceptions enabled within an extended
service call routine, an E_CTX error is returned if this service call is invoked from anextended service call routine.
[Supplemental Information]
This service call starts the task exception handling routine if all the conditions for starting the routine are met.

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µITRON4.0 Specification

sns_texVer. 4.00.00

Reference Task Exception Handling State[S][C Language API]BOOL state = sns_tex ( ) ;[Parameter]
None[Return Parameter]
BOOL
state

Task exception disabled state[Functional Description]
This service call returns TRUE if task exceptions are disabled for the task in the RUNNING state (which corresponds to the invoking task when this service call invokedfrom task contexts) and returns FALSE if task exceptions are enabled. If this service
call is invoked from non-task contexts and there is no task in the RUNNING state,
TRUE is returned.
[Supplemental Information]
Tasks that have no defined task exception handling routine always have task exceptions
disabled. Therefore, when the invoking task has no defined task exception handlingroutine, this service call returns TRUE.

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µITRON4.0 Specification

ref_texVer. 4.00.00

Reference Task Exception Handling State[C Language API]ER ercd = ref_tex ( ID tskid, T_RTEX *pk_rtex ) ;[Parameter]
ID
T_RTEX *tskid
pk_rtex[Return Parameter]ER
ercd

ID number of the task to be referenced
Pointer to the packet returning the task exception
handling state
E_OK for normal completion or error code

pk_rtex includes (T_RTEX type)
STAT
texstatTask exception handling state
TEXPTN
pndptnPending exception code
(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR
E_OBJ

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Parameter error (pk_rtex is invalid)
Object state error (specified task is in the DORMANT state,
the task exception handling routine is not defined)[Functional Description]
This service call references the state of the task exception handling for the task specified by tskid. The state of the task exception handling is returned through the packet
pointed to by pk_rtex.
texstat can take on any of the following values:
TTEX_ENATTEX_DIS

0x00
0x01

Task exception enabled state
Task exception disabled state

The pending exception code is returned through pndptn. If no unprocessed exception
request exists, pndptn is 0.
If tskid is TSK_SELF (= 0), the state of the invoking task is referenced.
If the task is in the DORMANT state or the task exception handling routine is notdefined for the task, an E_OBJ error is returned.

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4.4 Synchronization and Communication Functions
Synchronization and communication functions provide synchronization and communication between tasks through objects that are independent of the tasks. The objects are
semaphores, data queues, event flags, and mailboxes.
[Differences from the µITRON3.0 Specification]
Implementation of mailboxes are now limited to linked lists. Data queues have been
newly introduced and provide the same functionality as mailboxes but are implemented
with ring buffers.

4.4.1 Semaphores
A semaphore is an object used for mutual exclusion and synchronization. A semaphore
indicates availability and the number of unused resources by a resource count. Semaphore functions include the ability to create and delete a semaphore, to acquire andrelease resources, and to reference the state of a semaphore. A semaphore is an object
identified by an ID number. The ID number of a semaphore is called the semaphoreID.
A semaphore has an associated resource count and a wait queue. The resource countindicates the resource availability or the number of unused resources. The wait queue
manages the tasks waiting for resources from the semaphore. When a task releases a
semaphore resource, the resource count is incremented by 1. When a task acquires asemaphore resource, the resource count is decremented by 1. If a semaphore has noresources available or more precisely the resource count is 0, a task attempting toacquire a resource will wait in the wait queue until a resource is returned to the semaphore.
In order to avoid the case where too many resources are returned to a semaphore, each
semaphore has a maximum resource count indicating the maximum number of unused
resources available to the semaphore. If more resources are returned to the semaphore
than its maximum resource count, an error will be returned.
The following kernel configuration constant is defined for use with semaphore functions:
TMAX_MAXSEM

Maximum value of the maximum definable semaphore
resource count

The following data type packets are defined for creating and referencing semaphores:
typedef struct t_csem {ATR
sematr ;/* Semaphore attribute */UINT
isemcnt ; /* Initial semaphore resource count */UINTmaxsem ; /* Maximum semaphore resource count *//* Other implementation specific fields may be added. */125

µITRON4.0 Specification

Ver. 4.00.00} T_CSEM ;typedef struct t_rsem {IDwtskid ;/* ID number of the task at the head of thesemaphore’s wait queue */UINTsemcnt ; /* Current semaphore resource count *//* Other implementation specific fields may be added. */} T_RSEM ;The following represents the function codes for the semaphore service calls:
TFN_CRE_SEM
TFN_ACRE_SEM
TFN_DEL_SEM
TFN_SIG_SEM
TFN_ISIG_SEM
TFN_WAI_SEM
TFN_POL_SEM
TFN_TWAI_SEM
TFN_REF_SEM

–0x21
–0xc2
–0x22
–0x23
–0x75
–0x25
–0x26
–0x27
–0x28

Function code of cre_sem
Function code of acre_sem
Function code of del_sem
Function code of sig_sem
Function code of isig_sem
Function code of wai_sem
Function code of pol_sem
Function code of twai_sem
Function code of ref_sem[Standard Profile]
The Standard Profile requires support for semaphore functions except for dynamic creation and deletion of a semaphore (cre_sem, acre_sem, del_sem) and reference ofa semaphore state (ref_sem).
The Standard Profile requires that maximum resource count can be set to at least
65535. Although TMAX_MAXSEM does not have to be defined, if it is defined, it
must be equal to or greater than 65535.
[Rationale]
TMAX_MAXSEM is only used when semaphores are dynamically created. Since
dynamic semaphore creation does not have to be supported in the Standard Profile,
TMAX_MAXSEM does not have to be defined in this case.

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µITRON4.0 Specification

CRE_SEM
cre_sem
acre_semVer. 4.00.00

Create Semaphore (Static API)[S]

Create Semaphore
Create Semaphore (ID Number Automatic Assignment)[Static API]
CRE_SEM ( ID semid, { ATR sematr, UINT isemcnt,
UINT maxsem } ) ;[C Language API]ER ercd = cre_sem ( ID semid, T_CSEM *pk_csem ) ;ER_ID semid = acre_sem ( T_CSEM *pk_csem ) ;[Parameter]
ID

semid

ID number of the semaphore to be created (except
acre_sem)
T_CSEM * pk_csem Pointer to the packet containing the semaphore creation information (in CRE_SEM, packet contents
must be directly specified.)

pk_csem includes (T_CSEM type)
ATR
sematrSemaphore attribute
UINT
isemcnt Initial semaphore resource countUINT
maxsem Maximum semaphore resource count(Other implementation specific information may be added.)[Return Parameter]
cre_sem:ER

ercd

E_OK for normal completion or error code

acre_sem:
ER_ID

semid

ID number (positive value) of the created semaphore or error code

[Error Code]
E_ID
E_NOID
E_RSATR
E_PAR
E_OBJ

Invalid ID number (semid is invalid or unusable; only
cre_sem)
No ID number available (there is no semaphore ID assignable;
only acre_sem)
Reserved attribute (sematr is invalid or unusable)
Parameter error (pk_csem, isemcnt, or maxsem isinvalid)Object state error (specified semaphore is already registered;
only cre_sem)

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µITRON4.0 Specification

Ver. 4.00.00[Functional Description]
These service calls create a semaphore with an ID number specified by semid basedon the information contained in the packet pointed to by pk_csem. sematr is theattribute of the semaphore. isemcnt is the initial value of the resource count after creation of the semaphore. maxsem is the maximum resource count of the semaphore.
In CRE_SEM, semid is an integer parameter with automatic assignment. sematr isa preprocessor constant expression parameter.
acre_sem assigns a semaphore ID from the pool of unassigned semaphore IDs andreturns the assigned semaphore ID.
sematr can be specified as (TA_FIFO || TA_TPRI). If TA_FIFO (= 0x00) is specified, the semaphore’s wait queue will be in FIFO order. If TA_TPRI (= 0x01) is specified, the semaphore’s wait queue will be in task priority order.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the semaphore creation information.
The data types of isemcnt and maxsem have been changed from INT to UINT.
acre_sem has been newly added.

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del_semVer. 4.00.00

Delete Semaphore[C Language API]ER ercd = del_sem ( ID semid ) ;[Parameter]
ID

semid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the semaphore to be deleted
E_OK for normal completion or error code

Invalid ID number (semid is invalid or unusable)
Non-existent object (specified semaphore is not registered)[Functional Description]
This service call deletes the semaphore specified by semid.
[Supplemental Information]See Section 3.8 for information regarding handling tasks that are waiting for a resource
in a semaphore’s wait queue when the semaphore is deleted.

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sig_semisig_semVer. 4.00.00

Release Semaphore Resource

[S]
[S]

[C Language API]ER ercd = sig_sem ( ID semid ) ;ER ercd = isig_sem ( ID semid ) ;[Parameter]
ID

semid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXSE_QOVR

ID number of the semaphore to which resource isreleased
E_OK for normal completion or error code

Invalid ID number (semid is invalid or unusable)
Non-existent object (specified semaphore is not registered)
Queue overflow (release will exceed maximum resource
count)[Functional Description]
These service calls release one resource to the semaphore specified by semid. If any
tasks are waiting for the specified semaphore, the task at the head of the semaphore’s
wait queue is released from waiting. When this happens, the associated semaphore
resource count is not changed. The released task receives E_OK from the service callthat caused it to wait in the semaphore’s wait queue. If no tasks are waiting for the
specified semaphore, the semaphore resource count is incremented by 1.
These service calls return an E_QOVR error if incrementing the resource count by 1
will cause the count to exceed the maximum semaphore resource count. If this service
call is invoked from non-task contexts and has its execution delayed, an E_QOVR
error may not be returned, however the condition must still be checked.

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wai_sem
pol_sem
twai_semVer. 4.00.00

Acquire Semaphore Resource[S]

Acquire Semaphore Resource (Polling)[S]

Acquire Semaphore Resource (with Timeout)[S][C Language API]ER ercd = wai_sem ( ID semid ) ;ER ercd = pol_sem ( ID semid ) ;ER ercd = twai_sem ( ID semid, TMO tmout ) ;[Parameter]
ID

semid

TMO

tmout

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the semaphore from which resource isacquiredSpecified timeout (only twai_sem)
E_OK for normal completion or error code

Invalid ID number (semid is invalid or unusable)
Non-existent object (specified semaphore is not registered)
Parameter error (tmout is invalid; only twai_sem)
Forced release from waiting (accept rel_wai while waiting;
except pol_sem)
Polling failure or timeout (except wai_sem)
Waiting object deleted (semaphore is deleted while waiting;
except pol_sem)[Functional Description]
There service calls acquire one resource from the semaphore specified by semid. If
the resource count of the specified semaphore is 1 or more, the associated resource
count is decremented by 1. In this case, the invoking task is not moved to the WAITING state, but rather receives a normal return from the service call. If, on the other
hand, the resource count of the specified semaphore is 0, the invoking task is placed in
the semaphore’s wait queue and is moved to the waiting state for the semaphore. In
this case, the resource count remains unchanged at 0.
If there are already tasks in the wait queue, the invoking task is placed in the wait queueas described below. When the semaphore’s attribute has TA_TFIFO (= 0x00) set, theinvoking task is placed in the tail of the wait queue. When the attribute has TA_TPRI(= 0x01) set, the invoking task is placed in the wait queue in the order of the task’s priority. If the wait queue contains tasks with the same priority as the invoking task, theinvoking task is placed after those tasks.
pol_sem is a polling service call with the same functionality as wai_sem .
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twai_sem has the same functionality as wai_sem with an additional timeout feature.
tmout can be set to a positive number indicating a timeout duration or it can be set to
TMO_POL (= 0) or TMO_FEVR (= –1).
[Supplemental Information]
twai_sem acts the same as pol_sem if TMO_POL is specified in tmout as long as
no context error occurs. Also, twai_sem acts the same as wai_sem if TMO_FEVR
is specified in tmout.
[Differences from the µITRON3.0 Specification]
The name of the polling service call has been changed from preq_sem to pol_sem.

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ref_semVer. 4.00.00

Reference Semaphore State[C Language API]ER ercd = ref_sem ( ID semid, T_RSEM *pk_rsem ) ;[Parameter]ID
T_RSEM *semid
pk_rsem[Return Parameter]ER
ercd

ID number of the semaphore to be referenced
Pointer to the packet returning the semaphore state
E_OK for normal completion or error code

pk_rsem includes (T_RSEM type)ID
wtskidID number of the task at the head of the semaphore’s wait queueUINT
semcntCurrent semaphore resource count(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (semid is invalid or unusable)
Non-existent object (specified semaphore is not registered)
Parameter error (pk_rsem is invalid)[Functional Description]
This service call references the state of the semaphore specified by semid. The stateof the semaphore is returned through the packet pointed to by pk_rsem.
The ID number of the task at the head of the semaphore’s wait queue is returned
through wtskid. If no tasks are waiting for the semaphore’s resource, TSK_NONE(= 0) is returned instead.
The semaphore’s current resource count is returned through semcnt.
[Supplemental Information]
A semaphore cannot have wtskid ≠ TSK_NONE and semcnt ≠ 0 at the same time.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The ID
number of the task at the head of the wait queue is now returned instead of a boolean
value indicating whether a task is waiting or not. Based on this replacement, the nameand data type of the return parameter has been changed.
The data type of semcnt has been changed from INT to UINT. The order of parameters and of return parameters has been changed.

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4.4.2 Eventflags
An eventflag is a synchronization object that consists of multiple bits in a bit patternwhere each bit represents an event. Eventflag functions include the ability to create anddelete an eventflag, to set and clear an eventflag, to wait for an eventflag, and to reference the state of an eventflag. An eventflag is an object identified by an ID number.
The ID number of an eventflag is called the eventflag ID.
An eventflag has an associated bit pattern expressing the state of its events, and a wait
queue for tasks waiting on these events. Sometimes the bit pattern of an eventflag issimply called an eventflag. A task is able to set specified bits when an event occurs andis able to clear specified bits when necessary. Tasks waiting for events to occur will
wait until every specified bit in the eventflag bit pattern is set. Tasks waiting for an
eventflag are placed in the eventflag’s wait queue.
The following data type is used for eventflag functions:
FLGPTNBit pattern of the eventflag (unsigned integer)

The following kernel configuration constant is defined for use with eventflag functions:
TBIT_FLGPTN

The number of bits in an eventflag

The following kernel configuration constant is defined for use with eventflag functions:typedef struct t_cflg {ATR
flgatr ;FLGPTN
iflgptn ;/* Eventflag attribute *//* Initial value of the eventflag bit
pattern *//* Other implementation specific fields may be added. */} T_CFLG ;typedef struct t_rflg {IDwtskid ;/* ID number of the task at the head of theeventflag’s wait queue */FLGPTN
flgptn ;/* Current eventflag bit pattern *//* Other implementation specific fields may be added. */} T_RFLG ;The following represents the function codes for the eventflag service calls:
TFN_CRE_FLG
TFN_ACRE_FLG
TFN_DEL_FLG
TFN_SET_FLG
TFN_ISET_FLG
TFN_CLR_FLG
TFN_WAI_FLG
TFN_POL_FLG
TFN_TWAI_FLG
TFN_REF_FLG

–0x29
–0xc3
–0x2a
–0x2b
–0x76
–0x2c
–0x2d
–0x2e
–0x2f
–0x30

Function code of cre_flg
Function code of acre_flg
Function code of del_flg
Function code of set_flg
Function code of iset_flg
Function code of clr_flg
Function code of wai_flg
Function code of pol_flg
Function code of twai_flg
Function code of ref_flg

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µITRON4.0 Specification

Ver. 4.00.00[Standard Profile]
The Standard Profile requires support for eventflag functions except for dynamic creation and deletion of an eventflag (cre_flg, acre_flg, del_flg) and reference of aneventflag state (ref_flg).
The Standard Profile does not require support for multiple tasks waiting for an eventflag, i.e. eventflags with the TA_WMUL attribute.
The Standard Profile requires support for an eventflag’s bit pattern of at least 16 bits.
Therefore, TBIT_FLGPTN must be defined to be at least 16. The minimum bit widthof the data type for eventflag functions is as follows:
FLGPTN

16 bits or more

[Supplemental Information]
There is no limitation to the number of bits supported by an eventflag except when
implementing the Standard Profile. Therefore it is possible to supply an eventflag that
supports only 1 bit. Because the C language does not support a data type with an arbitrary bit width, the number of bits in a variable of FLGPTN type may actually be morethan the number of bits defined in TBIT_FLGPTN (the number of bits in an
eventflag).
[Differences from the µITRON3.0 Specification]
The data type of the parameter holding an eventflag bit pattern has been changed fromUINT to the new data type FLGPTN.

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µITRON4.0 Specification

CRE_FLG
cre_flg
acre_flg

Ver. 4.00.00

Create Eventflag (Static API)[S]

Create Eventflag
Create Eventflag (ID Number Automatic Assignment)[Static API]
CRE_FLG ( ID flgid, { ATR flgatr, FLGPTN iflgptn } ) ;[C Language API]ER ercd = cre_flg ( ID flgid, T_CFLG *pk_cflg ) ;ER_ID flgid = acre_flg ( T_CFLG *pk_cflg ) ;[Parameter]ID
T_CFLG *flgid
pk_cflg

ID number of the eventflag to be created (except
acre_flg)
Pointer to the packet containing the eventflag creation information (in CRE_FLG, packet contents
must be directly specified.)

pk_cflg includes (T_CFLG type)
ATR
flgatrEventflag attribute
FLGPTN
iflgptn
Initial value of eventflag bit pattern(Other implementation specific information may be added.)[Return Parameter]
cre_flg:ER

ercd

E_OK for normal completion or error code

acre_flg:
ER_ID

flgid

ID number (positive value) of the created eventflag
or error code

[Error Code]
E_ID
E_NOID
E_RSATR
E_PAR
E_OBJ

Invalid ID number (flgid is invalid or unusable; only cre_flg)
No ID number available (there is no eventflag ID assignable;
only acre_flg)
Reserved attribute (flgatr is invalid or unusable)
Parameter error (pk_cflg or iflgptn is invalid)
Object state error (specified eventflag is already registered;
only cre_flg)[Functional Description]
These service calls create an eventflag with an ID number specified by flgid based on
the information contained in the packet pointed to by pk_cflg. flgatr is the attributeof the eventflag. iflgptn is the initial value of the bit pattern after creation of the event136

µITRON4.0 Specification

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flag.
In CRE_FLG, flgid is an integer parameter with automatic assignment. flgatr is a
preprocessor constant expression parameter.
acre_flg assigns an eventflag ID from the pool of unassigned eventflag IDs and returns
the assigned eventflag ID.
flgatr can be specified as ((TA_TFIFO || TA_TPRI) | (TA_WSGL || TA_WMUL) |[TA_CLR]). If TA_TFIFO (= 0x00) is specified, the eventflag’s wait queue will be in
FIFO order. If TA_TPRI (= 0x01) is specified, the eventflag’s wait queue will be intask priority order. If TA_WSGL (= 0x00) is specified, only a single task is allowed to
be in the waiting state for the eventflag. If TA_WMUL (= 0x02) is specified, multiple
tasks are allowed to be in the waiting state for the eventflag. If TA_CLR (= 0x04) is
specified, the eventflag’s entire bit pattern will be cleared when a task is released fromthe waiting state for the eventflag.
[Standard Profile]
The Standard Profile does not require support for when TA_WMUL is specified in
flgatr.
[Supplemental Information]
A task in the waiting state for an eventflag is not always released from waiting according to its order in the wait queue. This is because when the task satisfies the releasecondition, it is released from waiting even if it is not at the head of the wait queue. For
example, even if an eventflag’s attribute has TA_TFIFO set, tasks are not always
released from the wait queue in FIFO order.
If TA_WSGL is specified in flgatr, the eventflag with the TA_TFIFO attributebehaves the same as the eventflag with the TA_TPRI attribute.
Multiple tasks cannot be released from the waiting state for an eventflag with the
TA_CLR attribute. This is because when a task is released from waiting, all of the bitsin the eventflag is cleared.
[Differences from the µITRON3.0 Specification]
The specification of clearing an eventflag has been moved from the wait mode parameter in wai_flg to the eventflag attribute. This change has been made because there isalmost never a case where some waiting tasks will require the bit pattern to be cleared
and some tasks will require the bit pattern to remain intact.
The functionality allowing the eventflag’s wait queue to be ordered by task priority
with the TA_TPRI attribute has been added.
The extended information has been removed from the eventflag creation information.
The data type of iflgptn have been changed from the UINT to FLGPTN. The valueof TA_WMUL has been changed.
acre_flg has been newly added.

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del_flg

Ver. 4.00.00

Delete Eventflag[C Language API]ER ercd = del_flg ( ID flgid ) ;[Parameter]
ID

flgid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the eventflag to be deleted
E_OK for normal completion or error code

Invalid ID number (flgid is invalid or unusable)
Non-existent object (specified eventflag is not registered)[Functional Description]
This service call deletes the eventflag specified by flgid.
[Supplemental Information]See Section 3.8 for information regarding handling tasks that are waiting in an
eventflag’s wait queue when the eventflag is deleted.

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µITRON4.0 Specification

set_flg
iset_flg

Ver. 4.00.00[S]

Set Eventflag[S][C Language API]ER ercd = set_flg ( ID flgid, FLGPTN setptn ) ;ER ercd = iset_flg ( ID flgid, FLGPTN setptn ) ;[Parameter]ID
FLGPTN

flgid
setptn[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR

ID number of the eventflag to be set
Bit pattern to set
E_OK for normal completion or error code

Invalid ID number (flgid is invalid or unusable)
Non-existent object (specified eventflag is not registered)
Parameter error (setptn is invalid)[Functional Description]
These service calls set the bits specified by setptn in the eventflag specified by flgid.
Specifically, the bit pattern of the eventflag is updated to the bit-wise OR of its bit pattern before the invocation of the service call with the value specified in setptn.
After the eventflag’s bit pattern is updated, any tasks that satisfy their release conditions are released from waiting. Specifically, each task in the eventflag’s wait queue ischecked starting from the head and is released from waiting if its release condition issatisfied. Each of the released tasks receives E_OK from the service call that caused it
to wait in the eventflag’s wait queue. It also receives the bit pattern of the eventflag satisfying the task’s releasing condition. If the eventflag’s attribute has TA_CLR(= 0x04) set, the service calls complete after clearing the entire bit pattern of the eventflag. If TA_CLR is not specified, the remaining tasks in the wait queue are checked tosee if they satisfy their release conditions. The service calls terminate after all tasks
have been checked. See the functional description of wai_flg for information abouttasks’ release conditions.
Multiple tasks can be released by a single invocation of set_flg if the eventflag’s
attribute has the TA_WMUL (= 0x02) attribute but not the TA_CLR attribute set.
When multiple tasks are released, they are released in the same order as in the eventflag’s wait queue. Therefore, among the same priority tasks that are moved to the
READY state, a task closer to the head of the wait queue will have higher precedence.
[Supplemental Information]
No action is required when all of the bits of setptn are 0.

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µITRON4.0 Specification

Ver. 4.00.00[Differences from the µITRON3.0 Specification]
The data type of setptn has been changed from UINT to FLGPTN.

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µITRON4.0 Specification

clr_flg

Ver. 4.00.00[S]

Clear Eventflag[C Language API]ER ercd = clr_flg ( ID flgid, FLGPTN clrptn ) ;[Parameter]ID
FLGPTN

flgid
clrptn[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR

ID number of the eventflag to be cleared
Bit pattern to clear (bit-wise negated)
E_OK for normal completion or error code

Invalid ID number (flgid is invalid or unusable)
Non-existent object (specified eventflag is not registered)
Parameter error (clrptn is invalid)[Functional Description]
This service call clears the bits in the eventflag specified by flgid that correspond to 0
bit in clrptn. Specifically, the bit pattern of the eventflag is updated to the bit-wise
AND of its bit pattern before the invocation of the service call with the value specified
in clrptn.
[Supplemental Information]
No action is required when all of the bits of clrptn are 1.
[Differences from the µITRON3.0 Specification]
The data type of clrptn has been changed from UINT to FLGPTN.

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µITRON4.0 Specification

wai_flg
pol_flg
twai_flg

Ver. 4.00.00

Wait for Eventflag[S]

Wait for Eventflag (Polling)[S]

Wait for Eventflag (with Timeout)[S][C Language API]ER ercd = wai_flg ( ID flgid, FLGPTN waiptn, MODE wfmode,
FLGPTN *p_flgptn ) ;ER ercd = pol_flg ( ID flgid, FLGPTN waiptn, MODE wfmode,
FLGPTN *p_flgptn ) ;ER ercd = twai_flg ( ID flgid, FLGPTN waiptn, MODE wfmode,
FLGPTN *p_flgptn, TMO tmout ) ;[Parameter]ID
FLGPTN
MODE
TMO

flgid
waiptnwfmodetmout[Return Parameter]ER
ercd
FLGPTN
flgptn[Error Code]
E_ID
E_NOEXS
E_PAR
E_ILUSE
E_RLWAIE_TMOUT
E_DLT

ID number of the eventflag to wait for
Wait bit pattern
Wait mode
Specified timeout (only twai_flg)
E_OK for normal completion or error code
Bit pattern causing a task to be released from waiting

Invalid ID number (flgid is invalid or unusable)
Non-existent object (specified eventflag is not registered)
Parameter error (waiptn, wfmode, p_flgptn, or tmout isinvalid)
Illegal service call use (there is already a task waiting for an
eventflag with the TA_WSGL attribute)
Forced release from waiting (accept rel_wai while waiting;
except pol_flg)
Polling failure or timeout (except wai_flg)
Waiting object deleted (eventflag is deleted while waiting;
except pol_flg)[Functional Description]
These service calls cause invoking task to wait until the eventflag specified by flgid
satisfies the release condition. The release condition is determined by the bit patternspecified by waiptn and the wait mode specified by wfmode. Once the release condition is satisfied, the bit pattern causing the release is returned through flgptn. Specifically, the following actions are performed.
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If the release condition is already satisfied when the service calls are invoked, the service calls complete without causing the invoking task to wait. The eventflag bit patternis still returned to the invoking task through flgptn. In addition, when the eventflag’s
attribute has TA_CLR set, all the bits in the eventflag’s bit pattern are cleared.
If the release condition is not satisfied, the invoking task is placed in the eventflag’s
wait queue and is moved to the waiting state for the eventflag.
When the eventflag’s attribute has TA_WSGL (= 0x00) set and another task is alreadywaiting in the eventflag’s wait queue, an E_ILUSE error is returned. This applies even
if the release condition is already satisfied.
wfmode can be specified as (TWF_ANDW || TWF_ORW). When wfmode has
TWF_ANDW (= 0x00) set, the release condition requires all the bits in waiptn to be
set. Conversely, when wfmode has TWF_ORW (= 0x01) set, the release condition
only requires at least one bit in waiptn to be set.
If there are already tasks in the wait queue, the invoking task is placed in the wait queueas described below. When the eventflag’s attribute has TA_TFIFO (= 0x00) set, theinvoking task is placed in the tail of the wait queue. When the attribute has TA_TPRI(= 0x01) set, the invoking task is placed in the wait queue in the order of the task’s priority. If the wait queue contains tasks with the same priority as the invoking task, theinvoking task is placed after those tasks.
pol_flg is a polling service call with the same functionality as wai_flg. twai_flg has
the same functionality as wai_sem with an additional timeout feature. tmout can be
set to a positive number indicating a timeout duration or it can be set to TMO_POL(= 0) or TMO_FEVR (= –1).
If waitpn is 0, an E_PAR error is returned.
[Supplemental Information]
twai_flg acts the same as pol_flg if TMO_POL is specified in tmout as long as nocontext error occurs. Also, twai_flg acts the same as wai_flg if TMO_FEVR is specified in tmout.
[Differences from the µITRON3.0 Specification]
The order of parameters and the return parameter have been changed. The data type of
waiptn and flgptn has been changed from UINT to FLGPTN, and the data type of
wfmode has been changed from UINT to MODE.
The clear specification in the wait mode (TWF_CLR) has been removed. Instead, an
eventflag attribute TA_CLR has been added. The value of TWF_ORW has beenchanged.
[Rationale]
The reason that an E_PAR error is returned when waiptn is 0 is because the releasecondition will never be satisfied.

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µITRON4.0 Specification

ref_flg

Ver. 4.00.00

Reference Eventflag Status[C Language API]ER ercd = ref_flg ( ID flgid, T_RFLG *pk_rflg ) ;[Parameter]ID
T_RFLG *flgid
pk_rflg[Return Parameter]ER
ercd

ID number of the eventflag to be referenced
Pointer to the packet returning the eventflag state
E_OK for normal completion or error code

pk_rflg includes (T_RFLG type)ID
wtskidID number of the task at the head of the eventflag’s
wait queue
FLGPTN
flgptnEventflag’s current bit pattern(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (flgid is invalid or unusable)
Non-existent object (specified eventflag is not registered)
Parameter error (pk_rflg is invalid)[Functional Description]
This service call references the state of the eventflag specified by parameter flgid. The
state of the eventflag is returned through the packet pointed to by pk_rflg.
The ID number of the task at the head of the eventflag’s wait queue is returned throughwtskid. If no tasks are waiting for the eventflag, TSK_NONE (= 0) is returned
instead.
The eventflag’s current bit pattern is returned through flgptn.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The ID
number of the task at the head of the wait queue is now returned instead of a boolean
value indicating whether a task is waiting or not. Based on this replacement, the nameand data type of the return parameter has been changed.
The data type of flgptn has been changed from UINT to FLGPTN. The order ofparameters and of return parameters has been changed.

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4.4.3 Data Queues
A data queue is an object used for synchronization and communication by sending or
receiving a one word message, called a data element. Data queue functions include theability to create and delete a data queue, to send, force-send and receive a data element
to/from a data queue, and to reference the state of a data queue. A data queue is anobject identified by an ID number. The ID number of a data queue is called the data
queue ID.
A data queue has an associated wait queue for sending a data element (send-wait
queue) and an associated wait queue for receiving a data element (receive-wait queue).
Also, a data queue has an associated data queue area used to store sent data elements.
A task sending a data element (notifying the occurrence of an event) places the data
element in the data queue. If there is no room in the data queue area, the task will be in
the sending waiting state for a data queue until there is room for the data element in thedata queue area. The task waiting to send the data element is placed in the data queue’s
send-wait queue. A task receiving a data element (waiting for an occurrence of anevent) removes a data element from the data queue. If there is no data in the data
queue, the task will be in the receiving waiting state until a data element is sent to thedata queue. The task waiting to receive a data element from the data queue is placed in
the data queue’s receive-wait queue.
Synchronous message passing can be performed by setting the number of data elements that can be stored in the data queue area to 0. The sending task and the receiving
task wait until the other calls the complimentary service call, at which time the data
element is transferred.
The one word data element to be sent and received can be an integer or the address of amessage located in a memory area shared by the sender and the receiver. A data element that is sent and received is copied from the sender to the receiver.
The following kernel configuration macro is defined for use with the data queue functions:
SIZE dtqsz = TSZ_DTQ ( UINT dtqcnt )This macro returns the total required size of the data queue area in bytes necessary to store dtqcnt data elements.
The following date types packets are defined for creating and referencing data queues:
typedef struct t_cdtq {ATR
dtqatr ;UINT
dtqcnt ;/* Data queue attribute *//* Capacity of the data queue area (thenumber of data elements) */VP
dtq ;/* Start address of the data queue area *//* Other implementation specific fields may be added. */} T_CDTQ ;typedef struct t_rdtq {145

µITRON4.0 Specification
ID

Ver. 4.00.00
stskid ;/* ID number of the task at the head of thedata queue’s send-wait queue */IDrtskid ;/* ID number of the task at the head of thedata queue’s receive-wait queue */UINT
sdtqcnt ; /* The number of data elements in the data
queue *//* Other implementation specific fields may be added. */} T_RDTQ ;The following represents the function codes for the data queue service calls:
TFN_CRE_DTQ
TFN_ACRE_DTQ
TFN_DEL_DTQ
TFN_SND_DTQ
TFN_PSND_DTQ
TFN_IPSND_DTQ
TFN_TSND_DTQ
TFN_FSND_DTQ
TFN_IFSND_DTQ
TFN_RCV_DTQ
TFN_PRCV_DTQ
TFN_TRCV_DTQ
TFN_REF_DTQ

–0x31
–0xc4
–0x32
–0x35
–0x36
–0x77
–0x37
–0x38
–0x78
–0x39
–0x3a
–0x3b
–0x3c

Function code of cre_dtq
Function code of acre_dtq
Function code of del_dtq
Function code of snd_dtq
Function code of psnd_dtq
Function code of ipsnd_dtq
Function code of tsnd_dtq
Function code of fsnd_dtq
Function code of ifsnd_dtq
Function code of rcv_dtq
Function code of prcv_dtq
Function code of trcv_dtq
Function code of ref_dtq[Standard Profile]
The Standard Profile requires support for data queue functions except for dynamic creation and deletion of a data queue (cre_dtq, acre_dtq, del_dtq) and reference of adata queue state (ref_dtq).
The Standard Profile does not require TSZ_DTQ to be defined.
[Supplemental Information]
Figure 4-1 shows the behavior of a data queue when the number of data elements thatcan be stored in the data queue is set to 0. In this figure, task A and task B are assumed
to be running asynchronously.
• If task A invokes snd_dtq first, task A is moved to the WAITING state until task B
invokes rcv_dtq. During this time, task A is in the sending waiting state for a data
queue.
• If, on the other hand, task B invokes rcv_dtq first, task B is moved to the WAITING
state until task A invokes snd_dtq. During this time, task B is in the receiving
waiting state for a data queue.
• When task A invokes snd_dtq and task B invokes rcv_dtq, the data transfer fromtask A to task B takes place. After this, both tasks are moved to the runnable state.
A data queue is assumed to be implemented as a ring buffer.
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µITRON4.0 Specification

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Task A

Task B

rcv_dtq ( dtqid )snd_dtq ( dtqid )Figure 4-1. Synchronous Communication through a Data Queue[Differences from the µITRON3.0 Specification]
This functionality has been newly added and has the same functionality as the mailboxof the µITRON3.0 Specification implemented with a ring buffer.

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µITRON4.0 Specification

CRE_DTQ
cre_dtq
acre_dtq

Ver. 4.00.00

Create Data Queue (Static API)[S]

Create Data Queue
Create Data Queue (ID Number Automatic Assignment)[Static API]
CRE_DTQ ( ID dtqid, { ATR dtqatr, UINT dtqcnt, VP dtq } ) ;[C Language API]ER ercd = cre_dtq ( ID dtqid, T_CDTQ *pk_cdtq ) ;ER_ID dtqid = acre_dtq ( T_CDTQ *pk_cdtq ) ;[Parameter]ID
T_CDTQ *dtqid
pk_cdtq

ID number of the data queue to be created (except
acre_dtq)
Pointer to the packet containing the data queue creation information (in CRE_DTQ, packet contents
must be directly specified.)

pk_cdtq includes (T_CDTQ type)
ATR
dtqatrData queue attributeUINT
dtqcntCapacity of the data queue area (the number of data
elements)
VP
dtq
Start address of the data queue area
(Other implementation specific information may be added.)[Return Parameter]
cre_dtq:ER

ercd

E_OK for normal completion or error code

acre_dtq:
ER_ID

dtqid

ID number (positive value) of the created data
queue or error code

[Error Code]
E_ID
E_NOID
E_NOMEM
E_RSATR
E_PAR
E_OBJ

Invalid ID number (dtqid is invalid or unusable; only
cre_dtq)
No ID number available (there is no data queue ID assignable;
only acre_dtq)
Insufficient memory (data queue area cannot be allocated)
Reserved attribute (dtqatr is invalid or unusable)
Parameter error (pk_cdtq, dtqcnt, or dtq is invalid)
Object state error (specified data queue is already registered;
only cre_dtq)

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µITRON4.0 Specification

Ver. 4.00.00[Functional Description]
These service calls create a data queue with an ID number specified by dtqid based on
the information contained in the packet pointed to by pk_cdtq. dtqatr is the attributeof the data queue. dtqcnt is the capacity of the data queue area: the maximum numberof data elements that may be stored in the data queue area. dtq is the start address ofthe data queue area.
In CRE_DTQ, dtqid is an integer parameter with automatic assignment. dtqatr is a
preprocessor constant expression parameter.
acre_dtq assigns a data queue ID from the pool of unassigned data queue IDs andreturns the assigned data queue ID.
dtqatr can be specified as (TA_TFIFO || TA_TPRI). If TA_TFIFO (= 0x00) is specified, the data queue’s send-wait queue will be in FIFO order. If TA_TPRI (= 0x01) is
specified, the data queue’s send-wait queue will be in task priority order.
The necessary area to hold up to dtqcnt data elements starts from dtq and is used as
the data queue area. An application program can calculate the size of the data queue
area necessary to hold dtqcnt number of data elements by using the TSZ_DTQ
macro. If dtq is NULL (= 0), the kernel allocates the necessary memory area. dtqcnt
may be specified as 0.
[Standard Profile]
The Standard Profile does not require support for when other values than NULL are
specified in dtq.
[Supplemental Information]
The data queue’s receive-wait queue always utilizes FIFO ordering. Also, a data element sent to a data queue does not have a priority. The data elements in a data queue isalways in FIFO order. However, when snd_dtq and fsnd_dtq are used at the sametime, there are cases where the data element sent by fsnd_dtq would be ahead of thedata element earlier sent by snd_dtq.

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del_dtq

Ver. 4.00.00

Delete Data Queue[C Language API]ER ercd = del_dtq ( ID dtqid ) ;[Parameter]
ID

dtqid

ID number of the data queue to be deleted[Return Parameter]ER
ercd

E_OK for normal completion or error code

[Error Code]
E_ID
E_NOEXS

Invalid ID number (dtqid is invalid or unusable)
Non-existent object (specified data queue is not registered)[Functional Description]
This service call deletes the data queue specified by dtqid. If the data queue area wasallocated by the kernel, the area is released.
[Supplemental Information]
The data elements in the data queue will be discarded. See Section 3.8 for information
regarding handling tasks that are waiting in the data queue’s send-wait queue andreceive-wait queue when the data queue is deleted.

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µITRON4.0 Specification

snd_dtq
psnd_dtq
ipsnd_dtq
tsnd_dtq

Ver. 4.00.00

Send to Data Queue[S]

Send to Data Queue (Polling)

[S]
[S]

Send to Data Queue (with Timeout)[S][C Language API]ER ercd = snd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = psnd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = ipsnd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = tsnd_dtq ( ID dtqid, VP_INT data, TMO tmout ) ;[Parameter]ID
VP_INT
TMO

dtqid
data
tmout

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the data queue to which the data element is sent
Data element to be sent
Specified timeout (only tsnd_dtq)
E_OK for normal completion or error code

Invalid ID number (dtqid is invalid or unusable)
Non-existent object (specified data queue is not registered)
Parameter error (tmout is invalid; only tsnd_dtq)
Forced release from waiting (accept rel_wai while waiting;
only snd_dtq and tsnd_dtq)
Polling failure or timeout (except snd_dtq)
Waiting object deleted (data queue is deleted while waiting;
only snd_dtq and tsnd_dtq)[Functional Description]
These service calls send the data element specified by data to the data queue specified
by dtqid. Specifically, the following actions are performed.
If there are already tasks in the data queue’s receive-wait queue, these service calls
send the data element to the task at the head of the receive-wait queue and release thetask from waiting. The released task receives E_OK from the service call that caused
it to wait in the receive-wait queue. It also receives the data element from the data
queue through data.
If no tasks are waiting in the data queue’s receive-wait queue, these service calls place
the data element to be sent at the tail of the data queue. If there is no room in the data
queue area, the invoking task is placed in the send-wait queue and is moved to thesending waiting state for the data queue.
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If there are already tasks in the send-wait queue, the invoking task is placed in thesend-wait queue as described below. When the data queue’s attribute has TA_FIFO(= 0x00) set, the invoking task is placed at the tail of the send-wait queue. When thedata queue’s attribute has TA_TPRI (= 0x01) set, the invoking task is placed in thesend-wait queue in the order of the task’s priority. If the send-wait queue contains
tasks with the same priority as the invoking task, the invoking task is placed after thosetasks.
psnd_dtq and ipsnd_dtq are polling service calls with the same functionality as
snd_dtq. tsnd_dtq has the same functionality as snd_dtq with an additional timeout feature. tmout can be set to a positive number indicating a timeout duration or it
can be set to TMO_POL (= 0) or TMO_FEVR (= –1).
psnd_dtq and ipsnd_dtq return an E_TMOUT error if no tasks are waiting in thereceive-wait queue and if there is no room for the data element in the data queue area.
If the service call is invoked from non-task contexts and has its execution delayed, an
E_TMOUT error may not be returned.
[Supplemental Information]
tsnd_dtq acts the same as psnd_dtq if TMO_POL is specified in tmout as long as
no context error occurs. Also, tsnd_dtq acts the same as snd_dtq if TMO_FEVR is
specified in tmout.

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µITRON4.0 Specification

fsnd_dtq
ifsnd_dtq

Ver. 4.00.00

Forced Send to Data Queue

[S]
[S]

[C Language API]ER ercd = fsnd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = ifsnd_dtq ( ID dtqid, VP_INT data ) ;[Parameter]ID
VP_INT

dtqid
data[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_ILUSEID number of the data queue to which the data element is sent
Data element to be sent to the data queue
E_OK for normal completion or error code

Invalid ID number (dtqid is invalid or unusable)
Non-existent object (specified data queue is not registered)
Illegal service call use (the capacity of the data queue area is0)[Functional Description]
These service calls forcibly send the data element specified by data to the data queue
specified by dtqid. Specifically, the following actions are performed.
If there are already tasks in the data queue’s receive-wait queue, these service calls
send the data element to the task at the head of the receive-wait queue and release thetask from waiting. The released task receives E_OK from the service call that caused
it to wait in the receive-wait queue. It also receives the data element from the data
queue through data.
If no tasks are waiting in the data queue’s receive-wait queue, these service calls place
the data element to be sent at the tail of the data queue. If there is no room in the data
queue area, these service calls reserve a space for the new data element by deleting thefirst data element in the data queue. The new data element is still placed at the tail ofthe data queue.
These service calls cannot forcibly send a data element when the capacity of the data
queue area is 0. If the capacity of the data queue area is 0, an E_ILUSE error isreturned.
[Supplemental Information]
These service calls force the data to be sent even if there are already tasks waiting tosend data in the send-wait queue.
If the capacity of the data queue area is 0, an E_ILUSE error is returned even if there153

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is a task waiting in the receive-wait queue.

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µITRON4.0 Specification

rcv_dtq
prcv_dtq
trcv_dtq

Ver. 4.00.00

Receive from Data Queue[S]

Receive from Data Queue (Polling)[S]

Receive from Data Queue (with Timeout)[S][C Language API]ER ercd = rcv_dtq ( ID dtqid, VP_INT *p_data ) ;ER ercd = prcv_dtq ( ID dtqid, VP_INT *p_data ) ;ER ercd = trcv_dtq ( ID dtqid, VP_INT *p_data, TMO tmout ) ;[Parameter]
ID

dtqid

TMO

tmout

[Return Parameter]ER
ercd
VP_INT
data[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the data queue from which a data element is received
Specified timeout (only trcv_dtq)
E_OK for normal completion or error code
Data element received from the data queue

Invalid ID number (dtqid is invalid or unusable)
Non-existent object (specified data queue is not registered)
Parameter error (p_data or tmout is invalid)
Forced release from waiting (accept rel_wai while waiting;
except prcv_dtq)
Polling failure or timeout (except rcv_dtq)
Waiting object deleted (data queue is deleted while waiting;
except prcv_dtq)[Functional Description]
These service calls receive a data element from the data queue specified by dtqid andreturns the data element through data. Specifically, the following actions are performed.
If the data queue already has data elements, these service calls remove the first data element from the data queue and return it through data. If there is a task in the data
queue’s send-wait queue, these service calls place the data element from the first task inthe send-wait queue at the tail of the data queue and release the task from waiting. The
released task receives E_OK from the service call that caused it to wait in thesend-wait queue.
If there are no data elements in the data queue and if there are tasks in the data queue’s
send-wait queue (this occurs when the capacity of the data queue area is 0), the data
element from the task at the head of the send-wait queue is returned through data, andthe task is released from waiting. The released task receives E_OK from the service
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call that caused it to wait in the send-wait queue.
If there are no data elements in the data queue and if there are no tasks in the send-wait
queue, the invoking task is placed in the receive-wait queue and moved to the receiving
waiting state for the data queue. If there are already tasks in the receive-wait queue, theinvoking task is placed at the tail of the receive-wait queue.
prcv_dtq is a polling service call with the same functionality as rcv_dtq. trcv_dtq
has the same functionality as rcv_dtq with an additional timeout feature. tmout canbe set to a positive number indicating a timeout duration or it can be set to TMO_POL(= 0) or TMO_FEVR (= –1).
[Supplemental Information]
trcv_dtq acts the same as prcv_dtq if TMO_POL is specified in tmout as long as
no context error occurs. Also, trcv_dtq acts the same as rcv_dtq if TMO_FEVR is
specified in tmout.

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µITRON4.0 Specification

ref_dtq

Ver. 4.00.00

Reference Data Queue State[C Language API]ER ercd = ref_dtq ( ID dtqid, T_RDTQ *pk_rdtq ) ;[Parameter]ID
T_RDTQ *dtqid
pk_rdtq[Return Parameter]ER
ercd

ID number of the data queue to be referenced
Pointer to the packet returning the data queue state
E_OK for normal completion or error code

pk_rdtq includes (T_RDTQ type)ID
stskidID number of the task at the head of the send-waitqueueIDrtskidID number of the task at the head of thereceive-wait queueUINT
sdtqcnt
The number of data elements in the data queue(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (dtqid is invalid or unusable)
Non-existent object (specified data queue is not registered)
Parameter error (pk_rdtq is invalid)[Functional Description]
This service call references the state of the data queue specified by dtqid. The state ofthe data queue is returned through the packet pointed to by pk_rdtq.
The ID number of the task at the head of the data queue’s send-wait queue is returned
through stskid. If no tasks are waiting to send a data element, TSK_NONE (= 0) is
returned instead.
The ID number of the task at the head of the data queue’s receive-wait queue isreturned through rtskid . If no tasks are waiting to receive a data element,
TSK_NONE (= 0) is returned instead.
The number of data elements currently in the data queue is returned through sdtqcnt.
[Supplemental Information]
A data queue cannot have rtskid ≠ TSK_NONE and sdtqcnt ≠ 0 at the same time.
When stskid ≠ TSK_NONE, sdtqcnt is equal to the capacity of the data queue area.

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4.4.4 Mailboxes
A mailbox is an object used for synchronization and communication by sending or
receiving a message placed in a shared memory. Mailbox functions include the ability
to create and delete a mailbox, to send and receive a message to/from a mailbox, and toreference the state of a mailbox. A mailbox is an object identified by an ID number.
The ID number of a mailbox is called the mailbox ID.
A mailbox has an associated message queue used to store sent messages and an associated wait queue for receiving messages. A task sending a message (notifying theoccurrence of an event) places the message to be sent in the message queue. A task
receiving a message from the mailbox (waiting for an occurrence of an event) removes
the first message from the message queue. If there is no message in the message queue,
the task will be in the receiving waiting state until a message is sent to the mailbox.
The task waiting to receive a message from the mailbox is placed in the mailbox’s wait
queue.
With mailbox functions, only the start address of the message placed in a shared memory is actually passed between tasks. The message itself is not copied.
The kernel maintains the messages in the message queue using a linked list. The application program must reserve an area to be used by the kernel for the linked list at thehead of each sent message. This reserved area is called the message header. A message packet is the area consisting of a message header followed by an area that is usedby the application to store a message body. The start address of the message packet ispassed as a parameter to the service calls that send a message, and it is returned as areturn parameter from the service calls that receive a message. An area for the message
priority is included in the message header when the message queue is ordered by message priorities.
The kernel modifies the contents of a message header, except the area for the message
priority, while the message is in a message queue (and when the message is to beplaced in a message queue). On the other hand, the application program must not modify the contents of a message header, including the message priority, while the message
is in a message queue. If the application modifies the contents of a message header, theresulting behavior is undefined. In addition to the case where the application program
directly modifies the contents of a message header, this rule also applies to the casewhere the application program passes the address of the message header to the kerneland makes the kernel modify its contents. Therefore, the behavior when a message
already in a message queue is resent to a mailbox is undefined.
The following data types are used for message headers:
T_MSG
T_MSG_PRI

Message header for a mailbox
Message header with a message priority for a mailbox

The definition and size of the T_MSG type are implementation-defined. The

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T_MSG_PRI type is defined using T_MSG type as follows:
typedef struct t_msg_pri {T_MSG
msgque ;PRI
msgpri ;} T_MSG_PRI ;/* Message header *//* Message priority */The following kernel configuration macro is defined for use with mailbox functions:
SIZE mprihdsz = TSZ_MPRIHD ( PRI maxmpri )This macro returns the total required size in bytes of the area for message queueheaders for each message priority, when the maximum message priority is
maxmpri.
The following data types packets are defined for creating and referencing mailboxes:
typedef struct t_cmbx {ATR
mbxatr ;/* Mailbox attribute */PRI
maxmpri ; /* Maximum message priority */VPmprihd ; /* Start address of the area for message
queue headers for each message
priority *//* Other implementation specific fields may be added. */} T_CMBX ;typedef struct t_rmbx {ID
wtskid ;/* ID number of the task at the head of
mailbox’s wait queue */T_MSG * pk_msg ; /* Start address of the message packet atthe head of the message queue *//* Other implementation specific fields may be added. */} T_RMBX ;The following represents the function codes for the mailbox service calls:
TFN_CRE_MBX
TFN_ACRE_MBX
TFN_DEL_MBX
TFN_SND_MBX
TFN_RCV_MBX
TFN_PRCV_MBX
TFN_TRCV_MBX
TFN_REF_MBX

–0x3d
–0xc5
–0x3e
–0x3f
–0x41
–0x42
–0x43
–0x44

Function code of cre_mbx
Function code of acre_mbx
Function code of del_mbx
Function code of snd_mbx
Function code of rcv_mbx
Function code of prcv_mbx
Function code of trcv_mbx
Function code of ref_mbx[Standard Profile]
The Standard Profile requires support for mailbox functions except for dynamic creation and deletion of a mailbox (cre_mbx, acre_mbx, del_mbx) and reference of a
mailbox state (ref_mbx).
The Standard Profile does not require TSZ_MPRIHD to be defined.
[Supplemental Information]
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In the mailbox functions, the number of messages that can be stored in a message
queue has no upper limit because the application program has the responsibility toreserve the area for message headers. Service calls for sending a message will not
move the invoking task to the WAITING state.
To make an application program portable to different kernels with different definitions
and sizes for message headers, the message packet should be defined as a C language
structure, and a field of T_MSG type or T_MSG_PRI type should be allocated at the
top of the message packet. In addition the message priority should be assigned to themsgpri field in T_MSG_PRI type. sizeof ( T_MSG ) or sizeof ( T_MSG_PRI )can be used to determine the size of the message header.
The area for a message packet may be dynamically allocated from a fixed-sized or variable-sized memory pool. It is also possible to allocate the area statically. A common
practice is that the sending task allocates a memory block from a memory pool andsends the block as a message packet to a mailbox, while the receiving task releases thememory block which is received as a message packet from the mailbox to the memory
pool.
[Differences from the µITRON3.0 Specification]
Implementations of mailboxes are now limited to linked lists.

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µITRON4.0 Specification

CRE_MBX
cre_mbx
acre_mbx

Ver. 4.00.00

Create Mailbox (Static API)[S]

Create Mailbox
Create Mailbox (ID Number Automatic Assignment)[Static API]
CRE_MBX ( ID mbxid, { ATR mbxatr, PRI maxmpri,
VP mprihd } ) ;[C Language API]ER ercd = cre_mbx ( ID mbxid, T_CMBX *pk_cmbx ) ;ER_ID mbxid = acre_mbx ( T_CMBX *pk_cmbx ) ;[Parameter]
ID

mbxid

ID number of the mailbox to be created (except:
acre_mbx)
T_CMBX * pk_cmbx Pointer to the packet containing the mailbox creation information (in CRE_MBX, packet contents
must be directly specified.)pk_cmbx includes (T_CMBX type)
ATR
mbxatrMailbox attribute
PRI
maxmpri Maximum message priority
VP
mprihdStart address of the area for message queue headers
for each message priority(Other implementation specific information may be added.)[Return Parameter]
cre_mbx:
ER

ercd

E_OK for normal completion or error code

acre_mbx:
ER_ID

mbxid

ID number (positive value) of created mailbox or
error code

[Error Code]
E_ID
E_NOID
E_NOMEM
E_RSATR
E_PAR

Invalid ID number (mbxid is invalid or unusable; only
cre_mbx)
No ID number available (there is no mailbox ID assignable;
only acre_mbx)
Insufficient memory (message queue header area cannot beallocated)
Reserved attribute (mbxatr is invalid or unusable)
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µITRON4.0 Specification
E_OBJ

Ver. 4.00.00

Object state error (specified mailbox is already registered;
only cre_mbx)[Functional Description]
These service calls create a mailbox with ID number specified by mbxid based on theinformation contained in the packet pointed to by pk_cmbx. mbxatr is the attributeof the mailbox. maxmpri is the maximum message priority of messages sent to themailbox. mprihd is the start address of the area for message queue headers for eachmessage priority. maxmpri and mprihd are valid only when TA_MPRI (= 0x02) is
specified in mbxatr.
In CRE_MBX, mbxid is an integer parameter with automatic assignment. mbxatr
and maxmpri are preprocessor constant expression parameters.
acre_mbx assigns a mailbox ID from the pool of unassigned mailbox IDs and andreturns the asigned mailbox ID.
mbxatr can be specified as ((TA_TFIFO || TA_TPRI) | (TA_MFIFO || TA_MPRI)).
If TA_TFIFO (= 0x00) is specified, the mailbox’s wait queue will be in FIFO order. If
TA_TPRI (= 0x01) is specified, the mailbox’s wait queue will be in task priority order.
Similarly, if TA_MFIFO (= 0x00) is specified, the mailbox’s message queue will be in
FIFO order, and if TA_MPRI (= 0x02) is specified, the message queue will be in message priority order.
If TA_MPRI is specified in mbxatr, the necessary area to hold the message queueheaders for each of the message priorities up to maxmpri starts from mprihd. An
application program can calculate the size of the necessary message queue header area
when the maximum message priority is maxmpri by using TSZ_MPRIHD macro.
If mprihd is NULL (= 0), the kernel allocates the necessary memory area.
maxmpri cannot be specified as 0. If specified, an E_PAR error is returned.
[Standard Profile]
The Standard Profile does not require support for when other values than NULL is
specified in mprihd.
[Supplemental Information]
The following must be considered when a message queue is prepared for each message
priority level using the message queue header area.
Preparing a message queue for each message priority level is effective when the number of the message priority levels is small. When the number of allowed message priority levels is large, this method requires a large memory area and thus is not practical.
Therefore, in order to handle the case where the message priority levels is large, thestructure of the message queue should be varied depending on the number of message
priority levels. For example, when the maximum priority level is below a certain
threshold value, a message queue is prepared for each message priority level. Whenthe maximum priority level falls above this threshold, all messages are managed in a
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single queue. In this case, TSZ_MPRIHD will return the same value for all values ofmaxmpri that are above the threshold value. maxmpri parameter to CRE_MBX isdefined to be a preprocessor constant expression parameter in order for the kernel configurator to create conditional directives involving maxmpri in the C language sourcecode and to modify the data structure in the kernel when maxmpri is above thethreshold value.
It is also possible to manage all messages in a single queue without using separate message queues for each message priority. In this kind of implementations,
TSZ_MPRIHD should be defined so that it returns a constant value, regardless of
maxmpri.
[Differences from the µITRON3.0 Specification]
The maximum message priority (maxmpri) and the start address of the area for message queue headers for each message priority (mprihd) have been added to the mailbox creation information. The extended information and the ring buffer size (animplementation-dependent information) have been removed.
acre_mbx has been newly aded.

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µITRON4.0 Specification

del_mbx

Ver. 4.00.00

Delete Mailbox[C Language API]ER ercd = del_mbx ( ID mbxid ) ;[Parameter]
ID

mbxid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the mailbox to be deleted
E_OK for normal completion or error code

Invalid ID number (mbxid is invalid or unusable)
Non-existent object (specified mailbox is not registered)[Functional Description]
This service call deletes the mailbox specified by mbxid. If the area for message
queue headers for each message priority was allocated by the kernel, it is released.
[Supplemental Information]
The messages in the message queue will be discarded. See Section 3.8 for information
regarding handling tasks that are waiting to receive a message in a mailbox’s wait
queue when the mailbox is deleted.

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snd_mbx

Ver. 4.00.00[S]

Send to Mailbox[C Language API]ER ercd = snd_mbx ( ID mbxid, T_MSG *pk_msg ) ;[Parameter]ID
T_MSG *

mbxid
pk_msg[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR

ID number of the mailbox to which the message issent
Start address of the message packet to be sent to themailbox
E_OK for normal completion or error code

Invalid ID number (mbxid is invalid or unusable)
Non-existent object (specified mailbox is not registered)
Parameter error (pk_msg is invalid, the message priority inthe message packet (msgpri) is invalid)[Functional Description]
This service call sends the message whose start address is specified by pk_msg to themailbox specified by mbxid. Specifically, the following actions are performed.
If there are already tasks in the mailbox’s wait queue, this service call sends the start
address of the message packet to the task at the head of the wait queue and releases thetask from waiting. The released task receives E_OK from the service call that caused
it to wait in the wait queue. It also receives the start address of the message packet
from the mailbox through pk_msg.
If no tasks are waiting in the mailbox’s wait queue, this service call places the message
packet to the message queue. When the mailbox’s attribute has TA_MFIFIO (= 0x00)
set, the message packet is placed at the tail of the message queue. When the mailbox’s
attribute has TA_MPRI (= 0x02) set, the message packet is placed in the message
queue in the order of its message priority. If the message queue contains messages
with the same priority as the newly sent message, the message is placed after thosemessages.
When the mailbox’s attribute has TA_MPRI (= 0x02) set, the message header of
T_MSG_PRI type is assumed to be at the head of the message packet pointed to by
pk_msg. The message’s priority is obtained from the msgpri field in the message
header.
[Differences from the µITRON3.0 Specification]
The name of the service call has been changed from snd_msg into snd_mbx.
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rcv_mbx
prcv_mbx
trcv_mbx

Ver. 4.00.00

Receive from Mailbox[S]

Receive from Mailbox (Polling)[S]

Receive from Mailbox (with Timeout)[S][C Language API]ER ercd = rcv_mbx ( ID mbxid, T_MSG **ppk_msg ) ;ER ercd = prcv_mbx ( ID mbxid, T_MSG **ppk_msg ) ;ER ercd = trcv_mbx ( ID mbxid, T_MSG **ppk_msg,
TMO tmout ) ;[Parameter]
ID

mbxid

TMO

tmout

[Return Parameter]ER
ercd
T_MSG *
pk_msg[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the mailbox from which a message is
received
Specified timeout (only trcv_mbx)
E_OK for normal completion or error code
Start address of the message packet received fromthe mailbox

Invalid ID number (mbxid is invalid or unusable)
Non-existent object (specified mailbox is not registered)
Parameter error (ppk_msg or tmout is invalid)
Forced release from waiting (accept rel_wai while waiting;
except prcv_mbx)
Polling failure or timeout (except rcv_mbx)
Waiting object deleted (mailbox is deleted while waiting;
except prcv_mbx)[Functional Description]
These service calls receive a message from the mailbox specified by mbxid and return
its start address through pk_msg. Specifically, the following actions are performed.
If the mailbox’s message queue already has messages, these service calls remove thefirst message packet from the message queue and return its start address throughpk_msg.
If there are no messages in the message queue, the invoking task is placed in the wait
queue and moved to the receiving waiting state for the mailbox.
If there are already tasks in the wait queue, the invoking task is placed in the wait queueas described below. When the mailbox’s attribute has TA_TFIFO (= 0x00) set, theinvoking task is placed at the tail of the wait queue. When the mailbox’s attribute has
TA_TPRI (= 0x01) set, the invoking task is placed in the wait queue in the order of the166µITRON4.0 Specification

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task’s priority. If the wait queue contains tasks with the same priority as the invoking
task, the invoking task is placed after those tasks.
prcv_mbx is a polling service call with the same functionality as rcv_mbx .
trcv_mbx has the same functionality as rcv_mbx with an additional timeout feature.
tmout can be set to a positive number indicating a timeout duration or it can be set to
TMO_POL (= 0) or TMO_FEVR (= –1).
[Supplemental Information]
trcv_mbx acts the same as prcv_mbx if TMO_POL is specified in tmout as longas no context error occurs. Also, trcv_mbx acts the same as rcv_mbx if
TMO_FEVR is specified in tmout.
[Differences from the µITRON3.0 Specification]
The names of the service calls have been changed from rcv_msg , prcv_msg ,trcv_msg to rcv_mbx, prcv_mbx, trcv_mbx, respectively. The order of parameters and of return parameters has been changed.

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µITRON4.0 Specification

ref_mbx

Ver. 4.00.00

Reference Mailbox State[C Language API]ER ercd = ref_mbx ( ID mbxid, T_RMBX *pk_rmbx ) ;[Parameter]ID
mbxid
ID number of the mailbox to be referenced
T_RMBX * pk_rmbx Pointer to the packet returning the mailbox state[Return Parameter]ER
ercd

E_OK for normal completion or error code

pk_rmbx includes (T_RMBX type)ID
wtskidID number of the task at the head of the mailbox’s
wait queue
T_MSG *
pk_msg Start address of the message packet at the head of
message queue(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (mbxid is invalid or unusable)
Non-existent object (specified mailbox is not registered)
Parameter error (pk_rmbx is invalid)[Functional Description]
This service call references the state of the mailbox specified by mbxid. The state of
the mailbox is returned through the packet pointed to by pk_rmbx.
The ID number of the task at the head of the mailbox’s wait queue is returned throughwtskid. If no tasks are waiting to receive a message, TSK_NONE (= 0) is returned
instead.
The start address of the message packet at the head of the mailbox’s message queue isreturned through pk_msg. If there is no message in the message queue, NULL (= 0)is returned instead.
[Supplemental Information]
A mailbox cannot have wtskid ≠ TSK_NONE and pk_msg ≠ NULL at the same
time.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The ID
number of the task at the head of the wait queue is now returned instead of a boolean
value indicating whether a task is waiting or not. Based on this replacement, the nameand data type of the return parameter has been changed.

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The order of parameters and of return parameters has been changed.

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4.5 Extended Synchronization and Communication
Functions
Extend synchronization and communication functions provide advanced synchronization and communication between tasks through objects that are independent of thetasks. The objects are mutexes, message buffers, and rendezvous ports.
[Standard Profile]
The Standard Profile does not require support for extended synchronization and communication functions.
[Differences from the µITRON3.0 Specification]
Mutex is a newly added feature.

4.5.1 Mutexes
A mutex is an object used for mutual exclusion of a shared resource among tasks.
Mutex supports the priority inheritance protocol and the priority ceiling protocol toavoid unbounded priority inversions among tasks competing for a shared resource.
Mutex functions includes the ability to create and delete a mutex, to lock and unlock a
mutex, and to reference the state of a mutex. A mutex is an object identified by an ID
number. The ID number of a mutex is called the mutex ID.
A mutex has a locked and unlocked state. It also has a wait queue for tasks waiting tolock the mutex. The kernel manages the task that locks each mutex and also the set ofmutexes a task locks. A task will try to lock a mutex before using a shared resource. Incase a mutex is already locked by another task, the task will be placed in the WAITING
state until the mutex is released. A task unlocks the mutex after using the sharedresource.
A mutex uses the priority inheritance protocol when its attribute has TA_INHERIT(= 0x02) set, and it uses the priority ceiling protocol when its attribute has
TA_CEILING (= 0x03) set. During mutex creation, if the TA_CEILING attribute is
specified, the ceiling priority parameter should be set to the maximum priority of thetasks that may lock the mutex. When a task tries to lock a mutex with the
TA_CEILING attribute and it has a higher base priority than the ceiling priority of the
mutex, an E_ILUSE error is returned. If chg_pri is invoked to set the base priority ofa task that has locked a mutex with the TA_CEILING attribute to a higher value thanthe mutex’s ceiling priority, chg_pri will return an E_ILUSE error.
When using these protocols, mutex operations change the current priority of tasks inorder to prevent unbounded priority inversion. The priority inheritance protocol andthe priority ceiling protocol require that the current priority of a task should always beequal to the highest of the three priorities below:

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µITRON4.0 Specification

Ver. 4.00.00• The base priority of the task
• The highest current priority among tasks waiting to lock one of the mutexes
with the TA_INHERIT attribute that are locked by the task
• The highest ceiling priority among mutexes with the TA_CEILING attributethat are locked by the task
This rule is called the strict priority control rule.
If the current priority of a task waiting for a mutex with the TA_INHERIT attribute ischanged by mutex operations or is changed by having its base priority changed by
chg_pri, the task that has the mutex locked may have to have its current prioritychanged. Such a change of priority is called transitive priority inheritance. Moreover,
if the latter task is waiting for a second mutex with the TA_INHERIT attribute, transitive priority inheritance needs to be applied to the task that has the second mutex
locked.
In addition to the strict priority control rule, the µITRON4.0 Specification defines
another priority control rule, called the simplified priority control rule, which limits theconditions under which the current priority is changed. The priority control rule used
is implementation-defined. Under the simplified priority control rule, when the current
priority of a task should be raised, it must be raised. However, when the current priority of a task should be lowered, it must be lowered only when the task no longer locks
any mutexes. In the case where the current priority of the task is lowered, it is changed
back to its base priority. More specifically, the current priority of a task is changed
under the following conditions:• When a higher-priority task begins to wait for a mutex with the
TA_INHERIT attribute that is locked by the task.
• When the current priority of a task waiting for a mutex with the
TA_INHERIT attribute that is locked by the task is changed to a higher priority than the task.
• When the task locks a mutex with the TA_CEILING attribute and with ahigher ceiling priority than the task’s current priority.
• When the task releases the last mutex that it locked.
The following actions are taken when the current priority of a task has been changed bymutex operations. When a task whose priority has been changed is in the runnable
state, the precedence of the task is changed according to its new priority. The resulting
precedence of the task among the tasks with the same priority is implementation-dependent. When a task whose priority has been changed is in a priority-orderedwait queue, the task’s position in the wait queue is changed according to the new priority. The resulting position of the task among the tasks of the same priority is implementation-dependent.
If a task terminates while it still has mutexes locked, the kernel unlocks all the mutexes
that it locked. The order of unlocking the mutexes is implementation-dependent. For

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more details about unlocking a mutex, see the functional description of unl_mtx.
The following data type packets are defined for creating and referencing mutexes:
typedef struct t_cmtx {ATR
mtxatr ;/* Mutex attribute */PRI
ceilpri ;/* Mutex ceiling priority *//* Other implementation specific fields may be added. */} T_CMTX ;typedef struct t_rmtx {IDhtskid ;/* ID number of the task that locks the
mutex */
ID
wtskid ;/* ID number of the task at the head of the
mutex’s wait queue *//* Other implementation specific fields may be added. */} T_RMTX ;The following represents the function codes for the mutex service calls:
TFN_CRE_MTX
TFN_ACRE_MTX
TFN_DEL_MTX
TFN_LOC_MTX
TFN_PLOC_MTX
TFN_TLOC_MTX
TFN_UNL_MTX
TFN_REF_MTX

–0x81
–0xc6
–0x82
–0x85
–0x86
–0x87
–0x83
–0x88

Function code of cre_mtx
Function code of acre_mtx
Function code of del_mtx
Function code of loc_mtx
Function code of ploc_mtx
Function code of tloc_mtx
Function code of unl_mtx
Function code of ref_mtx[Supplemental Information]
A mutex with the attribute TA_TFIFO or TA_TPRI has a similar functionality as asemaphore whose maximum count is 1: a binary semaphore. The differences are that amutex can only be unlocked by the task that locked it and that a mutex is unlocked by
the kernel when the locking task terminates.
The definition of the priority ceiling protocol described here is different from the priority ceiling protocol proposed in literature. More strictly, this protocol is sometimes
referred to as the highest locker protocol.
When mutex operations change the current priority of a task, and when the order of thetask within a wait queue is changed, the kernel may need to release the task or othertasks in the wait queue from waiting. See the functional descriptions of snd_mbf andget_mpl for details.
[Differences from the µITRON3.0 Specification]
The mutex is newly added feature. Mutexes are introduced as objects independent
from semaphores because supporting priority inheritance protocol for counting semaphores is difficult.

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Ver. 4.00.00[Rationale]
When mutex operations change the current priority of a task, the precedence among thetasks with the same priority are made implementation-dependent for the following reasons. Some applications might require frequent changes of the current priority throughthe use of mutexes, resulting in frequent task switches, which in turn is not desirable.
If precedence of the task among tasks of the same priority is determined to the lowest,
unnecessary task switches may occur. Ideally, precedence (and not priority) should be
inherited. However, such a specification would require a large overhead. For this reason, the precedence among tasks is left up to the implementation.

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µITRON4.0 Specification

CRE_MTX
cre_mtxacre_mtx

Ver. 4.00.00

Create Mutex (Static API)
Create Mutex
Create Mutex (ID Number Automatic Assignment)[Static API]
CRE_MTX ( ID mtxid, { ATR mtxatr, PRI ceilpri } ) ;[C Language API]ER ercd = cre_mtx ( ID mtxid, T_CMTX *pk_cmtx ) ;ER_ID mtxid = acre_mtx ( T_CMTX *pk_cmtx ) ;[Parameter]ID
T_CMTX *mtxid
pk_cmtx

ID number of the mutex to be created (except
acre_mtx)
Pointer to the packet containing the mutex creation
information (in CRE_MTX, the packet contents
must be directly specified.)pk_cmtx includes (T_CMTX type)
ATR
mtxatrMutex attribute
PRI
ceilpriMutex ceiling priority(Other implementation specific information may be added.)[Return Parameter]
cre_mtx:ER

ercd

E_OK for normal completion or error code

acre_mtx:
ER_ID

mtxid

ID number (positive value) of the created mutex or
error code

[Error Code]
E_ID
E_NOID
E_RSATR
E_PAR
E_OBJ

Invalid ID number (mtxid is invalid or unusable; only
cre_mtx)
No ID number available (there is no mutex ID assignable;
only acre_mtx)
Reserved attribute (mtxatr is invalid or unusable)
Parameter error (pk_cmtx or ceilpri is invalid)
Object state error (mutex is already registered; only
cre_mtx)[Functional Description]
These service calls create a mutex with an ID number specified by mtxid based on theinformation contained in the packet pointed to by pk_cmtx. mtxatr is the attribute174

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of the mutex. ceilpri is the mutex ceiling priority. ceilpri is only valid when mtxatr
has TA_CEILING (= 0x03) set.
In CRE_MTX, mtxid is an integer parameter with automatic assignment. mtxatr isa preprocessor constant expression parameter.
acre_mtx assigns a mutex ID from the pool of unassigned mutex IDs and returns theassigned mutex ID.
mtxatr can be specified as ( TA_TFIFO || TA_TPRI || TA_INHERIT ||TA_CEILING). If TA_FIFO (= 0x00) is specified, the mutex’s wait queue will be in
FIFO order. Otherwise, the mutex’s wait queue will be in task priority order. If
TA_INHERIT (= 0x02) is set, the current priority of a task is changed according to thepriority inheritance protocol. If TA_CEILING (= 0x03) is set, the current priority of atask is changed according to the priority ceiling protocol.

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µITRON4.0 Specification

del_mtx

Ver. 4.00.00

Delete Mutex[C Language API]ER ercd = del_mtx ( ID mtxid ) ;[Parameter]
ID

mtxid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the mutex to be deleted
E_OK for normal completion or error code

Invalid ID number (mtxid is invalid or unusable)
Non-existent object (specified mutex is not registered)[Functional Description]
This service call deletes the mutex specified by mtxid.
[Supplemental Information]
If the specified mutex has been locked by a task, del_mtx forces the task to unlock the
mutex it has locked. Therefore, if the mutex has either the TA_INHERIT or
TA_CEILING attribute, the current priority of the task that has locked the mutex mayneed to be changed. When the simplified priority control rule is applied, the current
priority of the locking task is changed only if after the deletion, no mutex remains
locked by the task.
The task that locked the mutex is not notified about the deletion of the mutex. Rather,
it will receive an error when it tries to unlock the mutex. If deleting a mutex will cause
an undesirable result for the task that is locking the mutex, a task that tries to delete themutex should first lock the mutex itself and then delete it.
See Section 3.8 for information regarding handling tasks that are waiting to lock a
mutex when the mutex is deleted.

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µITRON4.0 Specification

loc_mtx
ploc_mtx
tloc_mtx

Ver. 4.00.00

Lock Mutex
Lock Mutex (Polling)
Lock Mutex (with Timeout)[C Language API]ER ercd = loc_mtx ( ID mtxid ) ;ER ercd = ploc_mtx ( ID mtxid ) ;ER ercd = tloc_mtx ( ID mtxid, TMO tmout ) ;[Parameter]
ID
TMO

mtxid
tmout

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_ILUSE
E_RLWAIE_TMOUT
E_DLT

ID number of the mutex to be lockedSpecified timeout (only tloc_mtx)
E_OK for normal completion or error code

Invalid ID number (mtxid is invalid or unusable)
Non-existent object (specified mutex is not registered)
Parameter error (tmout is invalid; only tloc_mtx)
Illegal service call use (multiple locking of a mutex, ceiling
priority violation)
Forced release from waiting (accept rel_wai while waiting;
except ploc_mtx)
Polling failure or timeout (except loc_mtx)
Waiting object deleted (mutex is deleted while waiting; except
ploc_mtx)[Functional Description]
These service calls lock the mutex specified by mtxid. Specifically, if the mutex is notlocked, the service calls let the invoking task lock the mutex and return without moving
the invoking task to the WAITING state. If the mutex is locked, the invoking task isplaced in the mutex’s wait queue and is moved to the waiting state for the mutex.
If there are already tasks in the wait queue, the invoking task is placed in the wait queueas described below. When the mutex’s attribute has TA_TFIFO (= 0x00) set, theinvoking task is placed at the tail of the wait queue. Otherwise, the invoking task isplaced in the wait queue in the order of the task’s priority. If the wait queue contains
tasks with the same priority as the invoking task, the invoking task is placed after thosetasks.
If the invoking task has already locked the mutex, these service calls return an
E_ILUSE error. An E_ILUSE error will also be returned if the mutex has
TA_CEILING attribute set and if the invoking task has a base priority higher than the177µITRON4.0 Specification

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ceiling priority of the mutex.
ploc_mtx is a polling service call with the same functionality as loc_mtx. tloc_mtx
has the same functionality as loc_mtx with an additional timeout feature. tmout canbe set to a positive number indicating a timeout duration or it can be set to TMO_POL(= 0) or TMO_FEVR (= –1).
[Supplemental Information]
When a task invokes these service calls on the mutex with TA_INHERIT attribute thatis locked and is moved to the WAITING state, the current priority of the task that locks
a mutex is changed to the current priority of the invoking task if the latter’s current priority is lower than the current priority of the invoking task.
The current priority of a task that locks a mutex with TA_INHERIT attribute mayneed to be changed when a task that is waiting for the mutex is released from waiting
due to a timeout or with rel_wai. The simplified priority control rule does not perform
such a change.
When a task invokes these service calls on the mutex with TA_CEILING attribute andlocks it successfully, the current priority of the task is changed to the ceiling priority ofthe mutex if the ceiling priority is higher than the task’s current priority.
tloc_mtx acts the same as ploc_mtx if TMO_POL is specified in tmout as long as
no context error occurs. Also, tloc_mtx acts the same as loc_mtx if TMO_FEVR is
specified in tmout.

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µITRON4.0 Specification

unl_mtx

Ver. 4.00.00

Unlock Mutex[C Language API]ER ercd = unl_mtx ( ID mtxid ) ;[Parameter]
ID

mtxid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_ILUSEID number of the mutex to be unlocked
E_OK for normal completion or error code

Invalid ID number (mtxid is invalid or unusable)
Non-existent object (specified mutex is not registered)
Illegal service call use (the invoking task does not have thespecified mutex locked)[Functional Description]
This service call unlocks the mutex specified by mtxid. Specifically, if there are tasks
waiting to lock the mutex, the service call release the task at the head of the mutex’s
wait queue from waiting and let the released task lock the mutex. The task receives
E_OK from the service call that caused it to wait in the mutex’s wait queue. If no task
is waiting to lock the mutex, the service call moves the mutex to the unlocked state.
When the invoking task does not have the mutex locked, this service call returns an
E_ILUSE error.
[Supplemental Information]
The current priority of the task invoking this service call may need to be changed when
the specified mutex has the TA_INHERIT or TA_CEILING attribute set. If the simplified priority control rule is applied, the service call changes the current priority of
the invoking task only when no mutex remains locked by the task.

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ref_mtx

Ver. 4.00.00

Reference Mutex State[C Language API]ER ercd = ref_mtx ( ID mtxid, T_RMTX *pk_rmtx ) ;[Parameter]ID
T_RMTX *mtxid
pk_rmtx[Return Parameter]ER
ercd

ID number of the mutex to be referenced
Pointer to the packet returning the mutex state
E_OK for normal completion or error code

pk_rmtx includes (T_RMTX type)ID
htskidID number of the task locking the mutex
IDwtskidID number of the task at the head of the mutex’s
wait queue(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (mtxid is invalid or unusable)
Non-existent object (specified mutex is not registered)
Parameter error (pk_rmtx is invalid)[Functional Description]
This service call references the state of the mutex specified by mtxid. The state of the
mutex is returned through the packet pointed to by pk_rmtx.
The ID number of the task that has the mutex locked is returned through htskid. If notask has the mutex locked, TSK_NONE (= 0) is returned instead.
The ID number of the task at the head of the mutex’s wait queue is returned throughwtskid. If no tasks are waiting to lock the mutex TSK_NONE (= 0) is returned
instead.
[Supplemental Information]
A mutex cannot have htskid = TSK_NONE and wtskid ≠ TSK_NONE at the same
time.

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4.5.2 Message Buffers
A message buffer is an object used for synchronization and communication by sending
and receiving a variable-sized message. Message buffer functions include the ability tocreate and delete a message buffer, to send and receive a message to/from a message
buffer, and to reference the state of a message buffer. A message buffer is an object
identified by an ID number. The ID number of a message buffer is called the message
buffer ID.
A message buffer has an associated wait queue for sending a message (send-wait
queue) and an associated wait queue for receiving a message (receive-wait queue).
Also, a message buffer has an associated message buffer area to store the sent messages. A task sending a message (notifying the occurrence of an event) copies the message into the message buffer. If there is no room in the message buffer area, the task
will be in the sending waiting state for a message buffer until there is room for the message in the message buffer area. The task waiting to send the message is placed in themessage buffer’s send-wait queue. A task receiving a message (waiting for an occurrence of an event) removes a message from the message buffer. If there is no message
in the message buffer, the task will be in the receiving waiting state until a message issent to the message buffer. The task waiting to receive a message from the message
buffer is placed in the message buffer’s receive-wait queue.
Synchronous message passing can be performed by setting the size of the message
buffer area to 0. The sending task and the receiving task wait until the other calls thecomplimentary service call, at which time the message is transferred.
The following kernel configuration macro is defined for use with message buffer functions:
SIZE mbfsz = TSZ_MBF ( UINT msgcnt, UINT msgsz )This macro returns the approximate required size of the message buffer area inbytes necessary to store msgcnt messages each consisting of msgsz bytes.
This macro is only an estimation for determining the size of a message buffer area. It
cannot be used to determine the total required size of a message buffer area to store
messages with different sizes.
The following data type packets are defined for creating and referencing message buffers:
typedef struct t_cmbf {ATR
mbfatr ;/* Message buffer attribute */UINTmaxmsz ; /* Maximum message size (in bytes) */SIZE
mbfsz ;/* Size of message buffer area (in bytes) */VP
mbf ;/* Start sddress of message buffer area *//* Other implementation specific fields may be added. */} T_CMBF ;typedef struct t_rmbf {181

µITRON4.0 Specification
ID

Ver. 4.00.00
stskid ;/* ID number of the task at the head of themessage buffer’s send-wait queue */IDrtskid ;/* ID number of the task at the head of themessage buffer’s receive-wait queue */UINTsmsgcnt ; /* The number of messages in the message
buffer */SIZE
fmbfsz ;/* Size of free message buffer area in bytes,
without the minimum control areas *//* Other implementation specific fields may be added. */} T_RMBF ;The following represents the function codes for the message buffer service calls:
TFN_CRE_MBF
TFN_ACRE_MBF
TFN_DEL_MBF
TFN_SND_MBF
TFN_PSND_MBF
TFN_TSND_MBF
TFN_RCV_MBF
TFN_PRCV_MBF
TFN_TRCV_MBF
TFN_REF_MBF

–0x89
–0xc7
–0x8a
–0x8d
–0x8e
–0x8f
–0x91
–0x92
–0x93
–0x94

Function code of cre_mbf
Function code of acre_mbf
Function code of del_mbf
Function code of snd_mbf
Function code of psnd_mbf
Function code of tsnd_mbf
Function code of rcv_mbf
Function code of prcv_mbf
Function code of trcv_mbf
Function code of ref_mbf[Supplemental Information]
Figure 4-2 shows the behavior of a message buffer when the size of the message buffer
area is 0. In this figure, task A and task B are assumed to be running asynchronously.

Task A

Task B

rcv_mbf ( mbfid )snd_mbf ( mbfid )Figure 4-2. Synchronous Communication through a Message Buffer• If task A invokes snd_mbf first, task A is moved to the WAITING state until task B
invokes rcv_mbf. During this time, task A is in the sending waiting state for a message buffer.
• If, on the other hand, task B invokes rcv_mbf first, task B is moved to the WAITING state until task A invokes snd_mbf. During this time, task B is in the receiv182

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ing waiting state for a message buffer.
• When task A invokes snd_mbf and task B invokes rcv_mbf, the message transferfrom task A and task B takes place. After this, both tasks are moved to the runnable
state.
Tasks that are waiting to send a message to a message buffer will send their messages
in the order that the tasks are placed in the wait queue. An example is when task A tries
to send a 40 byte message to a message buffer, and task B tries to send a 10 byte message to the same message buffer. Assume that these tasks are placed in the wait queue
so that task A is ahead of task B. A third task then receives a message 20 byte long,resulting in 20 bytes of available area in the message buffer. Even though task B only
needs 10 bytes to send its message, it cannot do so until task A has sent its message.
However, an implementation-specific extension can add an attribute to the message
buffer that will allow task B to send its message before task A in this example.
A message buffer transfers a variable-sized message through copying. It is different
from a data queue in that it transfers variable-sized messages. It is different from a
mailbox in that it copies the messages.
A message buffer is assumed to be implemented as a ring buffer.
If a message buffer is used for the kernel’s error log (for recording errors that cannot bereported to the processing unit that invoked a service call), a message buffer with an ID
number of (–4) can be used. Furthermore, message buffers with ID numbers (–3) and(–2) can be used when message buffers are used inside the kernel to communicate withdebug support functions. Limiting the access to these message buffers from application programs is also allowed.
[Differences from the µITRON3.0 Specification]
Whether tasks should send messages according to their order in the wait queue or
according to which task can send a message first was implementation-dependent in theµITRON3.0 Specification. The µITRON4.0 Specifications has determined the former
order to be standard.

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CRE_MBF
cre_mbf
acre_mbf

Ver. 4.00.00

Create Message Buffer (Static API)
Create Message Buffer
Create Message Buffer (ID Number Automatic Assignment)[Static API]
CRE_MBF ( ID mbfid, { ATR mbfatr, UINT maxmsz, SIZE mbfsz,
VP mbf } ) ;[C Language API]ER ercd = cre_mbf ( ID mbfid, T_CMBF *pk_cmbf ) ;ER_ID mbfid = acre_mbf ( T_CMBF *pk_cmbf ) ;[Parameter]
ID

mbfid

T_CMBF * pk_cmbf

ID number of the message buffer to be created(except acre_mbf)
Pointer to the packet containing the message buffer
creation information (in CRE_MBF, packet contents must be directly specified.)pk_cmbf includes (T_CMBF type)
ATR
mbfatrMessage buffer attributeUINT
maxmsz Maximum message size (in bytes)
SIZE
mbfsz
Size of message buffer area (in bytes)
VP
mbf
Start address of message buffer area
(Other implementation specific information may be added.)[Return Parameter]
cre_mbf:ER

ercd

E_OK for normal completion or error code

acre_mbf:
ER_ID

mbfid

ID number (positive value) of the created message
buffer or error code

[Error Code]
E_ID
E_NOID
E_NOMEM
E_RSATR
E_PAR
E_OBJ

Invalid ID number (mbfid is invalid or unusable; only
cre_mbf)
No ID number available (there is no message buffer ID
assignable; only acre_mbf)
Insufficient memory (message buffer area cannot be allocated)
Reserved attribute (mbfatr is invalid or unusable)
Parameter error (pk_cmbf, maxmsz, mbfsz, or mbf isinvalid)Object state error (message buffer is already registered; only184

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cre_mbf)[Functional Description]
These service calls create a message buffer with an ID number specified by mbfid
based on the information contained in the packet pointed to by pk_cmbf. mbfatr is
the attribute of the message buffer. maxmsz is the maximum size in bytes of the message that can be sent to the message buffer. mbfsz is the size of the message buffer
area in bytes. mbf is the start address of the message buffer area.
In CRE_MBF, mbfid is an integer parameter with automatic assignment. mbfatr isa preprocessor constant expression parameter.
acre_mbf assigns a message buffer ID from the pool of unassigned message buffer
IDs and returns the assigned message buffer ID.
mbfatr can be specified as (TA_TFIFO || TA_TPRI). If TA_TFIFO (= 0x00) is
specified, the message buffer’s send-wait queue will be in FIFO order. If TA_TPRI(= 0x01) is specified, the message buffer’s send-wait queue will be in task priority
order.
The memory area starting from mbf and whose size is mbfsz is used as the message
buffer area. Because the information for message management is also placed in themessage buffer area, the whole message buffer area cannot be used to store messages.
An application program can estimate the size to be specified in mbfsz by using the
TSZ_MBF macro. If mbf is NULL (= 0), the kernel allocates the necessary memoryarea in bytes specified by mbfsz. mbfsz may be specified as 0.
When maxmsz is specified as 0, an E_PAR error is returned.
[Supplemental Information]
The message buffer’s receive-wait queue always utilizes the FIFO ordering. Also, themessages in a message buffer is always in FIFO order.
[Differences from the µITRON3.0 Specification]
In µITRON3.0, the TA_TPRI attribute of a message buffer indicated that thereceive-wait queue is priority-ordered. In µITRON4.0, it has changed to indicate thatthe send-wait queue is priority-ordered. This is because the priority-ordered send-wait
queue is more effective than priority-ordered receive-wait queue.
The start address of the message buffer area (mbf) has been added to the message
buffer creation information. The extended information has been removed. The parameter name has been changed from bufsz to mbfsz and the order of maxmsz andmbfsz in the creation information packet has been exchanged. The data type ofmaxmsz has been changed from INT to UINT and that of mbfsz has been changed
from INT to SIZE.
acre_mbf has been newly added.

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del_mbf

Ver. 4.00.00

Delete Message Buffer[C Language API]ER ercd = del_mbf ( ID mbfid ) ;[Parameter]
ID

mbfid

[Return Parameter]ER
ercd

ID number of the message buffer to be deleted
E_OK for normal completion or error code

[Error Code]
E_ID
E_NOEXS

Invalid ID number (mbfid is invalid or unusable)
Non-existent object (specified message buffer is not registered)[Functional Description]
This service call deletes the message buffer specified by mbfid. If the message buffer
area was allocated by the kernel, the area is released.
[Supplemental Information]
The messages in the message buffer will be discarded. See Section 3.8 for information
regarding handling tasks that are waiting in the message buffer’s send-wait queue andreceive-wait queue when the message buffer is deleted.

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snd_mbf
psnd_mbf
tsnd_mbf

Ver. 4.00.00

Send to Message buffer
Send to Message buffer (Polling)
Send to Message buffer (with Timeout)[C Language API]ER ercd = snd_mbf ( ID mbfid, VP msg, UINT msgsz ) ;ER ercd = psnd_mbf ( ID mbfid, VP msg, UINT msgsz ) ;ER ercd = tsnd_mbf ( ID mbfid, VP msg, UINT msgsz,
TMO tmout ) ;[Parameter]
ID

mbfid

VP
UINT
TMO

msg
msgsz
tmout

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the message buffer to which the message is sent
Start address of the message to be sent
Size of the message to be sent (in bytes)
Specified timeout (only tsnd_mbf)
E_OK for normal completion or error code

Invalid ID number (mbfid is invalid or unusable)
Non-existent object (specified message buffer is not registered)
Parameter error (msg, msgsz, tmout is invalid)
Forced release from waiting (accept rel_wai while waiting;
except psnd_mbf)
Polling failure or timeout (except snd_mbf)
Waiting object deleted (message buffer is deleted while waiting; except psnd_mbf)[Functional Description]
These service calls send a message to the message buffer specified by mbfid. The
message to be sent is placed in the memory area starting from the address specified by
msg and its size in bytes is specified by msgsz. Specifically, the following actions are
performed.
If there are already tasks in the message buffer’s receive-wait queue, the task at thehead of the receive-wait queue is selected to receive the message. These service calls
copy the sent message to the memory area specified by the task for receiving a message
and release the task from waiting. The released task receives the size of the sent message ( msgsz ) as the return value of the service call that caused it to wait in thereceive-wait queue.
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If no tasks are waiting in the message buffer’s receive-wait queue, the behavior of these
service calls depends on whether there is a task already waiting to send its message
before the invoking task. These service calls will copy the sent message to the tail ofthe message buffer if either: 1) no task is waiting to send a message to the specified
message buffer, or 2) the message buffer has the TA_TPRI (= 0x01) attribute set andthe priorities of the other tasks that are waiting to send messages are lower than the
invoking task. If neither of these conditions is satisfied, or if there is no room in themessage buffer area to store the sent message, the invoking task is placed in thesend-wait queue and is moved to the sending waiting state for the message buffer.
If there are already tasks in the message buffer’s send-wait queue, the invoking task isplaced in the send-wait queue as described below. When the message buffer’s attribute
has TA_TFIFO (= 0x00) set, the invoking task is placed at the tail of the send-wait
queue. When the message buffer’s attribute has TA_TPRI (= 0x01) set, the invoking
task is placed in the send-wait queue in the order of the task’s priority. If the send-wait
queue contains tasks with the same priority as the invoking task, the invoking task isplaced after those tasks.
When the first task in the send-wait queue has changed as the result of releasing a task
in the wait queue from waiting with rel_wai, ter_tsk, or a timeout, the actions, whenpossible, to make the tasks send messages starting from the new first task in the wait
queue are necessary. Since the specific actions are similar to the actions to be taken
after rcv_mbf has removed a message from the message buffer, see the functionaldescription of rcv_mbf for more details. The same actions are also necessary when
the first task in the send-wait queue has changed as the result of changing the priorityof a task in the wait queue by chg_pri or mutex operations.
psnd_mbf is a polling service call with the same functionality as snd_mbf .
tsnd_mbf has the same functionality as snd_mbf with an additional timeout feature.
tmout can be set to a positive number indicating a timeout duration or it can be set to
TMO_POL (= 0) or TMO_FEVR (= –1).
When msgsz is larger than the maximum message size of the message buffer, an
E_PAR error is returned. An E_PAR error is also returned when msgsz is 0.
[Supplemental Information]
tsnd_mbf acts the same as psnd_mbf if TMO_POL is specified in tmout as longas no context error occurs. Also, tsnd_mbf acts the same as snd_mbf if
TMO_FEVR is specified in tmout.
[Differences from the µITRON3.0 Specification]
The order of the parameters has been changed. The data type of msgsz has beenchanged from INT to UINT.

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µITRON4.0 Specification

rcv_mbf
prcv_mbf
trcv_mbf

Ver. 4.00.00

Receive from Message Buffer
Receive from Message Buffer (Polling)
Receive from Message Buffer (with Timeout)[C Language API]ER_UINT msgsz = rcv_mbf ( ID mbfid, VP msg ) ;ER_UINT msgsz = prcv_mbf ( ID mbfid, VP msg ) ;ER_UINT msgsz = trcv_mbf ( ID mbfid, VP msg, TMO tmout ) ;[Parameter]
ID

mbfid

VP

msg

TMO

tmout

[Return Parameter]
ER_UINT msgsz[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the message buffer from which a message is received
Start address of the memory area to store thereceived message
Specified timeout (only trcv_mbf)
Size of the received message (in byte, positive
value) or error code

Invalid ID number (mbfid is invalid or unusable)
Non-existent object (specified message buffer is not registered)
Parameter error (msg or tmout is invalid)
Forced release from waiting (accept rel_wai while waiting;
except prcv_mbf)
Polling failure or timeout (except rcv_mbf)
Waiting object deleted (message buffer is deleted while waiting; except prcv_mbf)[Functional Description]
These service calls receive a message from the message buffer specified by mbfid andstores it in the memory area starting from the address specified by msg. The size ofthe received message in bytes is returned through msgsz. Specifically, the following
actions are performed.
If the message buffer already has messages, these service calls copy the first message tothe memory area starting from the address specified by msg and return the message
size through msgsz. The copied message is deleted from the message buffer area. If
there are tasks in the message buffer’s send-wait queue, the service calls check if there
is enough room for the message of the task at the head of the wait queue after deleting
the received message. If there is enough room, the message of the task at the head of
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the wait queue is copied to the tail of the message buffer and the task is released fromwaiting. The released task receives E_OK from the service call that caused it to wait in
the wait queue. When some tasks still remain in the send-wait queue after the releaseof the task, the same actions must be repeated on the new head task in the wait queue.
If there are no messages in the message buffer and if there are tasks in the message
buffer’s send-wait queue (this occurs when the size of the message buffer area is too
small for the message of the task at the head of the wait queue), the message from thetask at the head of the send-wait queue is copied to the memory area starting from theaddress specified by msg. The size of the copied message is returned through msgsz.
The task is released from waiting and receives E_OK from the service call that caused
it to wait in the send-wait queue.
If there are no messages in the message buffer and if there are no tasks in the send-wait
queue, the invoking task is placed in the receive-wait queue and moved to the receiving
waiting state for the message buffer. If there are already tasks in the receive-wait
queue, the invoking task is placed at the tail of the receive-wait queue.
prcv_mbf is a polling service call with the same functionality as rcv_mbf.
trcv_mbf has the same functionality as rcv_mbf with an additional timeout feature.
tmout can be set to a positive number indicating a timeout duration or it can be set to
TMO_POL (0) or TMO_FEVR (–1).
[Supplemental Information]
If these service calls release more than one task from waiting, the order of release corresponds with the order in which the tasks are placed in the wait queue. Therefore,among the same priority tasks moved to the runnable state, the task closer to the headof the wait queue has higher precedence.
trcv_mbf acts the same as prcv_mbf if TMO_POL is specified in tmout as long as
no context error occurs. Also, trcv_mbf acts the same as rcv_mbf if TMO_FEVR is
specified in tmout.
[Differences from the µITRON3.0 Specification]
The size of the received message (msgsz) is now returned as the return value of theservice calls. The order of parameters has been changed. The data type of msgsz has
been changed from INT to UINT (the actual type though is ER_UINT).

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µITRON4.0 Specification

ref_mbf

Ver. 4.00.00

Reference Message Buffer State[C Language API]ER ercd = ref_mbf ( ID mbfid, T_RMBF *pk_rmbf ) ;[Parameter]ID
T_RMBF *mbfid
pk_rmbf[Return Parameter]ER
ercd

ID number of the message buffer to be referenced
Pointer to the packet returning the message buffer
state
E_OK for normal completion or error code

pk_rmbf includes (T_RMBF type)ID
stskidID number of the task at the head of the send-waitqueueIDrtskidID number of the task at the head of thereceive-wait queueUINT
smsgcnt The number of messages in the message buffer
SIZE
fmbfszSize of free message buffer area in bytes, without
the minimum control areas(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (mbfid is invalid or unusable)
Non-existent object (specified message buffer is not registered)
Parameter error (pk_rmbf is invalid)[Functional Description]
This service call references the state of the message buffer specified by mbfid. The
state of the message buffer is returned through the packet pointed to by pk_rmbf.
The ID number of the task at the head of the message buffer’s send-wait queue isreturned through stskid. If no tasks are waiting to send a message, TSK_NONE(= 0) is returned instead.
The ID number of the task at the head of the message buffer’s receive-wait queue isreturned through rtskid. If no tasks are waiting to receive a message, TSK_NONE(= 0) is returned instead.
The number of messages currently in the message buffer is returned throughsmsgcnt.
The size of the minimum control area subtracted from the size of the free message
buffer area in bytes is returned through fmbfsz. Specifically, fmbfsz is the maximum

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message size that can be stored in the free message buffer area when there is notenough room for a message with the maximum message size. If the message buffer hasenough room to store a message with the maximum message size, fmbfsz is theapproximate total size of messages that can be stored in the free message buffer area.
[Supplemental Information]
A message with smaller size than fmbfsz may not always be sent at once without
entering the WAITING state. This happens if there are tasks already waiting to send amessage to the message buffer (when stskid ≠ TSK_NONE).
A message buffer cannot have tskid ≠ TSK_NONE and smsgcnt ≠ 0 at the sametime. When stskid ≠ TSK_NONE, fmbfsz is smaller than the maximum message
size.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The ID
number of the task at the head of each wait queue is now returned instead of a boolean
value indicating whether a task is waiting or not. The number of messages in the message buffer is now returned instead of the size of the message to be received next.
Based on these replacements, the names and data types of the return parameters havebeen changed. The size of the minimum control area is excluded from the size returned
through fmbfsz in order to make the returned value strictly standardized to the message size when the free message buffer area is small.
The name of the return parameter frbufsz has been changed to fmbfsz and its data
type has been changed from INT to SIZE. The order of parameters and of returnparameters has been changed.

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4.5.3 Rendezvous
The rendezvous feature is used for synchronization and communication between tasks.
It supports a procedure to handle a processing request from one task to another task andthe return of the result to the requesting task. The object used to coordinate this task
interaction is called a rendezvous port. The rendezvous feature is typically used torealize a client/server model communication, but it also provides a more flexible synchronous communication model.
Rendezvous functions include the ability to create and delete a rendezvous port, torequest a processing at a rendezvous port (calling rendezvous), to accept a processing
request at a rendezvous port (accepting rendezvous), to return a processed result (terminating rendezvous), to forward a processing request to another rendezvous port (forwarding rendezvous), and to reference the state of a rendezvous port and of arendezvous. A rendezvous port is an object identified with an ID number. The ID
number of a rendezvous port is called the rendezvous port ID.
A task which requests a processing at a rendezvous port (the client task) calls for a rendezvous by specifying a rendezvous port, a rendezvous condition, and a message that
contains information about the requested processing. The message is referred to as thecalling message. A task that receives a processing request (the server task) accepts therendezvous by specifying the rendezvous port and the rendezvous condition.
A rendezvous condition is specified by a bit pattern. A rendezvous is only establishedwhen the bit patterns of the rendezvous conditions of both the calling task and theaccepting task match. The match is performed by taking the logical AND of the corresponding bits. If the result is not 0, the rendezvous is established. The calling task will
be in the calling waiting state for the rendezvous until the rendezvous is established.
On the other hand, the accepting task will be in the accepting waiting state for the rendezvous until the rendezvous is established.
When a rendezvous is established, the calling message is transferred from the callingtask to the accepting task. The calling task is moved to the termination waiting state
for the rendezvous and waits for the processing to be completed. The accepting task isreleased from the accepting waiting state for the rendezvous and executes the requested
processing. Once the accepting task completes its processing, it returns the result tothe calling task as a return message, and the rendezvous is terminated. At this time, thecalling task is released from the termination waiting state for the rendezvous.
A rendezvous port has an associated call-wait queue to hold the tasks in the calling
waiting state for a rendezvous and an accept-wait queue to hold the tasks in the accepting waiting state for a rendezvous. Once a rendezvous is established, the two tasks aredetached from the rendezvous port. A rendezvous port does not have a wait queue tohold the tasks that are in the termination waiting state for a rendezvous. Also, it does
not have information about the two tasks involved with the requested processing.

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The kernel assigns an object number to a rendezvous in order to distinguish multiple
rendezvous. The object number of a rendezvous is called the rendezvous number. The
process for assigning rendezvous numbers is implementation-dependent. However, therendezvous number should at least include information regarding the task that called
the rendezvous. Each rendezvous should have a unique rendezvous number if possible.
For example, if the same task calls a rendezvous port twice, the first and second rendezvous should have different rendezvous numbers.
The following data types are used for rendezvous functions:
RDVPTNRDVNO

Bit pattern of the rendezvous condition (unsigned integer)
Rendezvous number

The following kernel configuration constant is defined for use with rendezvous functions:
TBIT_RDVPTN

The number of bits in a rendezvous condition (thenumber of bits of RDVPTN type)The following data type packets are defined for creating and referencing rendezvous
ports and rendezvous:
typedef struct t_cpor {ATR
poratr ;/* Rendezvous port attribute */UINTmaxcmsz ; /* Maximum calling message size (inbytes) */UINT
maxrmsz ; /* Maximum return message size (inbytes) *//* Other implementation specific fields may be added. */} T_CPOR ;typedef struct t_rpor {IDctskid ;/* ID number of the task at the head of therendezvous port’s call-wait queue */IDatskid ;/* ID number of the task at the head of therendezvous port’s accept-wait queue *//* Other implementation specific fields may be added. */} T_RPOR ;typedef struct t_rrdv {ID
wtskid ;/* ID number of the task in the termination
waiting state for the rendezvous *//* Other implementation specific fields may be added. */} T_RRDV ;The following represents the function codes for rendezvous service calls:
TFN_CRE_POR
TFN_ACRE_POR
TFN_DEL_POR
TFN_CAL_POR
TFN_TCAL_POR

–0x95
–0xc8
–0x96
–0x97
–0x98

Function code of cre_por
Function code of acre_por
Function code of del_por
Function code of cal_por
Function code of tcal_por

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TFN_ACP_POR
TFN_PACP_POR
TFN_TACP_POR
TFN_FWD_RDV
TFN_RPL_RDV
TFN_REF_POR
TFN_REF_RDV

–0x99
–0x9a
–0x9b
–0x9c
–0x9d
–0x9e
–0x9f

Function code of acp_por
Function code of pacp_por
Function code of tacp_por
Function code of fwd_rdv
Function code of rpl_rdv
Function code of ref_por
Function code of ref_rdv[Supplemental Information]
A rendezvous is a synchronization and communication function which was introducedby the ADA language specification and is based on CSP (Communicating Sequential
Processes). However, the ADA rendezvous is a part of the language specification andits premise is different from the µITRON4.0 Specification rendezvous. In particular,
the rendezvous offered by a real-time kernel is intended to be a primitive for realizing
the language rendezvous. There are several differences between the ADA rendezvous
and the µITRON4.0 Specification rendezvous. Because of this, the rendezvous port ofthe µITRON4.0 Specification cannot always be used in realizing the ADA rendezvous.
Figure 4-3 shows the behavior of a rendezvous. In this figure, task A and task B are
assumed to be running asynchronously.

Task A

Task B

acp_por ( porid )cal_por ( porid )rpl_rdv ( rdvno )Figure 4-3. Rendezvous Operation• If task A invokes cal_por first, task A is moved to the WAITING state until task B
invokes acp_por. During this time, task A is in the calling waiting state for the rendezvous.
• If, on the other hands, task B invokes acp_por first, task B is moved to the WAITING state until task A invokes cal_por. During this time, task B is in the accepting
waiting state for the rendezvous.
• When task A invokes cal_por and task B invokes acp_por, the rendezvous isestablished. When this happens, task B is released from waiting while task A
remains in the WAITING state. Task A, at this time, is in the termination waiting
state for the rendezvous.
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µITRON4.0 Specification

Ver. 4.00.00• Once task B invokes rpl_rdv, task A is released from waiting. Both tasks are
moved to the runnable state.
One example of assigning a rendezvous number is to use the ID number of the task thatcalled the rendezvous as the lower bits, and then assign a serial number to the remaining upper bits. So if the task ID is a 16-bit value, the rendezvous number should bemade 32 bits by adding a 16-bit serial value.
[Differences from the µITRON3.0 Specification]
The term rendezvous port is now used instead of port.
The data type of the parameter that contains the rendezvous condition bit pattern has
been changed from UINT to the new data type RDVPTN. The data type for a rendezvous number has been changed from RNO to RDVNO.
[Rationale]
Although a rendezvous feature can be realized by combining other synchronization andcommunication features, writing application programs involving return messages withrendezvous functions is much easier and more efficient. For example, a rendezvous
does not need an area to store messages because the two tasks wait until the message
transfer is completed.
When a task calls a rendezvous port multiple times, each rendezvous number must be
unique if possible for the following reason. Assume that a task is in the termination
waiting state for a rendezvous and that the task is released from waiting due to timeout
or forced release. After being released, if it calls a rendezvous port again that is successfully established, the rendezvous numbers of the previous and the current rendezvous would be the same. When another task tries to terminate the previous rendezvous,
the current one would be terminated by mistake if they have the same number. By
assigning two different numbers to two different rendezvous and by recording the rendezvous number with the waiting task, an error can be detected when the first rendezvous is terminated.

196

µITRON4.0 Specification

CRE_POR
cre_poracre_porVer. 4.00.00

Create Rendezvous Port (Static API)
Create Rendezvous Port
Create Rendezvous Port (ID Number Automatic Assignment)[Static API]
CRE_POR ( ID porid, { ATR poratr, UINT maxcmsz,
UINT maxrmsz } ) ;[C Language API]ER ercd = cre_por ( ID porid, T_CPOR *pk_cpor ) ;ER_ID porid = acre_por ( T_CPOR *pk_cpor ) ;[Parameter]ID
T_CPOR *porid
pk_cporID number of the rendezvous port to be created(except acre_por)
Pointer to the packet containing the rendezvous port
creation information (in CRE_POR, packet contents must be directly specified.)

pk_cpor includes (T_CPOR type)
ATR
poratrRendezvous port attributeUINT
maxcmsz Maximum calling message size (in bytes)
UINT
maxrmsz Maximum return message size (in bytes)(Other implementation specific information may be added.)[Return Parameter]
cre_por:ER

ercd

E_OK for normal completion or error code

acre_por:
ER_ID

porid

ID number (positive value) of the created rendezvous port or error code

[Error Code]
E_ID
E_NOID
E_RSATR
E_PAR
E_OBJ

Invalid ID number (porid is invalid or unusable; only
cre_por)No ID number available (there is no rendezvous port ID
assignable; only acre_por)
Reserved attribute (poratr is invalid or unusable)
Parameter error (pk_cpor, maxcmsz, or maxrmsz isinvalid)Object state error (specified rendezvous port is already registered; only cre_por)

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µITRON4.0 Specification

Ver. 4.00.00[Functional Description]
These service calls create a rendezvous port with an ID number specified by porid
based on the information contained in the packet pointed to by pk_cpor. poratr is
the rendezvous port attribute. maxcmsz is the maximum size in bytes of a calling
message. maxrmsz is the maximum size in bytes of a returned message.
In CRE_POR, porid is an integer parameter with automatic assignment. poratr is a
preprocessor constant expression parameter.
acre_por assigns a rendezvous port ID from the pool of unassigned rendezvous port
IDs and returns the assigned rendezvous port ID.
poratr can be specified as (TA_TFIFO || TA_TPRI). If TA_TFIFO (= 0x00) is speci fi e d , t h e r e n d e z vo u s p o r t ’s c a l l - wa i t q u e u e w i l l b e i n F I F O o r d e r. I f
TA_TPRI(= 0x01) is specified, the rendezvous port’s call-wait queue will be in taskpriority order.
maxcmsz and maxrmsz may be specified as 0.
[Supplemental Information]
The rendezvous port’s accept-wait queue always utilizes FIFO ordering.
[Differences from the µITRON3.0 Specification]
By specifying the TA_TRPI attribute, a rendezvous port’s call-wait queue will now be
in task priority order.
The extended information has been removed from the rendezvous port creation information. The data types of maxcmsz and maxrmsz have been changed from INT to
UINT.
acre_por has been newly added.

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µITRON4.0 Specification

del_porVer. 4.00.00

Delete Rendezvous Port[C Language API]ER ercd = del_por ( ID porid ) ;[Parameter]
ID

porid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the rendezvous port to be deleted
E_OK for normal completion or error code

Invalid ID number (porid is invalid or unusable)
Non-existent object (specified rendezvous port is not registered)[Functional Description]
This service call deletes the rendezvous port specified by porid.
[Supplemental Information]
Deleting a rendezvous port does not affect an already established rendezvous. The
deletion is not reported to a task that has accepted a rendezvous and is already executing the requested processing. The task that called the rendezvous and is in the termination waiting state for the rendezvous will still continue waiting. Moreover, atermination of the rendezvous is executed normally even if the rendezvous port isalready deleted.
See Section 3.8 for information regarding handling tasks that are waiting to call or
accept a rendezvous at the rendezvous port when the rendezvous port is deleted.

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µITRON4.0 Specification

cal_por
tcal_porVer. 4.00.00

Call Rendezvous
Call Rendezvous (with Timeout)[C Language API]ER_UINT rmsgsz = cal_por ( ID porid, RDVPTN calptn, VP msg,
UINT cmsgsz ) ;ER_UINT rmsgsz = tcal_por ( ID porid, RDVPTN calptn, VP msg,
UINT cmsgsz, TMO tmout ) ;[Parameter]ID
RDVPTN

porid
calptn

VP

msg

UINT
TMO

cmsgsztmout[Return Parameter]
ER_UINT rmsgsz[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the rendezvous port to be called
Bit pattern of the rendezvous condition at the calling side
Start address of the calling message and of thememory area to store the return message
Calling message size (in bytes)
Specified timeout (only tcal_por)
Return message size (in bytes, positive value or 0)
or error code

Invalid ID number (porid is invalid or unusable)
Non-existent object (specified rendezvous port is not registered)
Parameter error (calptn, msg, cmsgsz, or tmout isinvalid)
Forced release from waiting (accept rel_wai while waiting)
Polling failure or timeout (only tcal_por)
Waiting object deleted (rendezvous port is deleted while waiting)[Functional Description]
These service calls call for a rendezvous at the port specified by porid with the rendezvous condition specified by calptn. The start address of the calling message is specified by msg and its size in bytes is specified by cmsgsz. The service calls store thereturn message in the memory area starting from msg and return its size in bytes
through rmsgsz. Specifically, the following actions are performed.
If there is a task in the accepting waiting state for the rendezvous at the rendezvous
port, these service calls establish a rendezvous if the rendezvous conditions of the
invoking task and the waiting task match. If there are more than one task in the accept200

µITRON4.0 Specification

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ing waiting state for the rendezvous, these service calls check their rendezvous conditions one by one starting from the task at the head of the accept-wait queue. The
service calls establish a rendezvous with the first task that matches the rendezvous condition.
When a rendezvous is established, these service calls assign a rendezvous number tothe established rendezvous and move the invoking task to the termination waiting state
for the rendezvous. The service calls also copy the calling message into the memoryarea specified by the accepting task, which was in the accepting waiting state for therendezvous. The service calls then release the task from waiting. The released task
receives the calling message size (cmsgsz) as the return value of the service call thatcaused it to wait in the accept-wait queue and the assigned rendezvous number throughrdvno.
If no tasks are waiting to accept a rendezvous at the specified rendezvous port, or if
none of the waiting tasks has a matching rendezvous condition, the invoking task isplaced in the call-wait queue and is moved to the calling waiting state for the rendezvous.
If there are already tasks in the rendezvous port’s call-wait queue, the invoking task isplaced in the call-wait queue as described below. When the rendezvous port’s attribute
has TA_TFIFO (= 0x00) set, the invoking task is placed at the tail of the call-wait
queue. When rendezvous port’s attribute has TA_TPRI (= 0x01) set, the invoking task
is placed in the call-wait queue in the order of the task’s priority. If the call-wait queue
contains tasks with the same priority as the invoking task, the invoking tasks is placed
after those tasks.
tcal_por has same functionality as cal_por with an additional timeout feature. If therendezvous does not terminate after a period specified by tmout starting from whentcal_por is called, tcal_por returns an E_TMOUT error. tmout can be set to
TMO_FEVR (= –1) in addition to a positive number indicating a timeout duration.
When TMO_POL (= 0) is specified, an E_PAR error is returned.
If tcal_por is invoked and results in a timeout after it establishes a rendezvous, the status of the rendezvous cannot be recovered to its former state before it was established.
This is an exception to the rule stating that “side effects due to a service call that returns
an error code do not arise.” In this case, an error is reported to the accepting task when
the task tries to terminate the rendezvous. This also applies to the case where a task is
forcibly released from the termination waiting state for the rendezvous with rel_wai.
In this case, the service call returns an E_RLWAI error. On the contrary, since deletinga rendezvous port does not affect an already established rendezvous, the service callnever returns an E_DLT error once the rendezvous is established.
An E_PAR error is returned when calptn is 0 or when cmsgsz exceeds the maximum calling message size. cmsgsz may be specified as 0.

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µITRON4.0 Specification

Ver. 4.00.00[Supplemental Information]
When there is a possibility that a rendezvous might be forwarded, the application
should allocate enough memory area, starting from the address specified by msg, tostore a return message with the maximum size regardless of the expected return message size. The application should also assume that the contents of the allocated memory area will be destroyed. This is because when the rendezvous is forwarded, thecalling message may be copied to the memory area starting from the address specified
by msg.
tcal_por acts the same as cal_por if TMO_FEVR is specified in tmout.
[Differences from the µITRON3.0 Specification]
The interpretation of timeout in tcal_por has been changed. As a result, pcal_por
became unnecessary and is removed from the µITRON4.0 Specification. tcal_por
returns an E_PAR error if TMO_POL is specified in tmout.
A calling message with a size of 0 is now allowed.
The return message size (rmsgsz) is now returned as the return value of the service
calls. The data type of calptn has been changed from UINT to RDVPTN. The datatypes of cmsgsz and rmsgsz have been changed from INT to UINT (the actual typethough is ER_UINT for rmsgsz). The order of parameters and of return parameters
has been changed.
[Rationale]
The reason an E_PAR error is returned when 0 is specified for calptn is that a rendezvous is never established in this case, which in turn would never release the invoking
task from calling waiting state for the rendezvous.

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µITRON4.0 Specification

acp_por
pacp_portacp_porVer. 4.00.00

Accept Rendezvous
Accept Rendezvous (Polling)
Accept Rendezvous (with Timeout)[C Language API]ER_UINT cmsgsz = acp_por ( ID porid, RDVPTN acpptn,
RDVNO *p_rdvno, VP msg ) ;ER_UINT cmsgsz = pacp_por ( ID porid, RDVPTN acpptn,
RDVNO *p_rdvno, VP msg ) ;ER_UINT cmsgsz = tacp_por ( ID porid, RDVPTN acpptn,
RDVNO *p_rdvno, VP msg, TMO tmout ) ;[Parameter]
ID

porid

RDVPTN

acpptn

VP

msg

TMO

tmout

[Return Parameter]
ER_UINT cmsgsz
RDVNO[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

rdvno

ID number of the rendezvous port where a rendezvous is acceptedBit pattern of the rendezvous condition at theaccepting side
Start address of the memory area to store the calling
messageSpecified timeout (only tacp_por)
Calling message size (in bytes, positive value or 0)
or error code
Rendezvous number of the established rendezvous

Invalid ID number (porid is invalid or unusable)
Non-existent object (specified rendezvous port is not registered)
Parameter error (acpptn, msg, or tmout is invalid)
Forced release from waiting (accept rel_wai while waiting;
except pacp_por)
Polling failure or timeout (except acp_por)
Waiting object deleted (rendezvous port is deleted while waiting; except pacp_por)[Functional Description]
These service calls accept a rendezvous at the rendezvous port specified by porid withthe rendezvous condition specified by acpptn. The calling message is stored in thememory area starting from the address specified by msg and its size in bytes isreturned through cmsgsz. The rendezvous number of the established rendezvous is203

µITRON4.0 Specification

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returned through rdvno. Specifically, the following actions are performed.
If there is a task in the calling waiting state for the rendezvous at the rendezvous port,these service calls establish a rendezvous if the rendezvous conditions of the invoking
task and the waiting task match. If there are more than one task in the calling waiting
state for the rendezvous, these service calls check their rendezvous conditions one by
one starting from the task at the head of the call-wait queue. The service calls establish
a rendezvous with the first task that matches the rendezvous condition.
When a rendezvous is established, these service calls assign a rendezvous number tothe established rendezvous and return the rendezvous number through rdvno. The
service calls also copy the calling message of the calling task, which was in the calling
waiting state for the rendezvous, to the memory area starting from the address specified
by msg and return the calling message size through cmsgsz. The task is thenremoved from the rendezvous port’s call-wait queue and is moved to the termination
waiting state for the rendezvous.
If no tasks are waiting to call a rendezvous at the specified rendezvous port, or if noneof the waiting tasks has a matching rendezvous condition, the invoking task is placed in
the accept-wait queue and is moved to the accepting waiting state for the rendezvous.
If there are already tasks in the accept-wait queue, the invoking task is placed at the tailof the accept-wait queue.
pacp_por is a polling service call with the same functionality as acp_por.
tacp_por has the same functionality as acp_por with an additional timeout feature.
tmout can be set to a positive number indicating a timeout duration or it can be set to
TMO_POL (= 0) or TMO_FEVR (= –1).
An E_PAR error is returned when acpptn is 0.
[Supplemental Information]
A task that has established a rendezvous with another task with acp_por may accept arendezvous again with acp_por before the previous rendezvous has been terminated.
The new rendezvous can be accepted at either the same rendezvous port as the previously established one or at another rendezvous port. If the same rendezvous port isused, the task can have multiple established rendezvous at the same rendezvous port.
Furthermore, the calling task of the previously established rendezvous can be released
from waiting either by timeout or forced release. When the task calls the rendezvous
again, the task can have multiple rendezvous with the other task at the same rendezvous
port.
tacp_por acts the same as pacp_por if TMO_POL is specified in tmout as long as
no context error occurs. Also, tacp_por acts the same as acp_por if TMO_FEVR is
specified in tmout.
[Differences from the µITRON3.0 Specification]
The calling message size (cmsgsz) is now returned as the return value of the service
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calls. The data type of acpptn has been changed from UINT to RDVPTN. The data
type of rdvno has been changed from RNO to RDVNO. The data type of cmsgsz
has been changed from INT to UINT (the actual type though is ER_UINT). The orderof parameters and of return parameters has been changed.
[Rationale]
The reason an E_PAR error is returned when 0 is specified for acpptn is that a rendezvous is never established in this case, which in turn would never release the invoking task from accepting waiting state for the rendezvous.

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µITRON4.0 Specification

fwd_porVer. 4.00.00

Forward Rendezvous[C Language API]ER ercd = fwd_por ( ID porid, RDVPTN calptn, RDVNO rdvno,
VP msg, UINT cmsgsz ) ;[Parameter]
ID

porid

RDVPTN

calptn

RDVNO
VP
UINT

rdvno
msg
cmsgsz[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_ILUSE

E_OBJ

ID number of the rendezvous port to which the rendezvous is forwarded
Bit pattern of the rendezvous condition at the calling side
Rendezvous number to be forwarded
Start address of the calling message
Calling message size (in bytes)
E_OK for normal completion or error code

Invalid ID number (porid is invalid or unusable)
Non-existent object (specified rendezvous port is not registered)
Parameter error (calptn, msg, or cmsgsz is invalid)
Illegal service call use (maximum return message size of therendezvous port to which the rendezvous is forwarded is toolarge)
Object state error (rdvno is invalid)[Functional Description]
This service call forwards the rendezvous specified by rdvno with the rendezvous condition specified by calptn to the rendezvous port specified by porid . The start
address of the calling message after forwarding is specified by msg and its size inbytes is specified by cmsgsz.
When fwd_por is invoked, the result is the same as if the task that called the rendezvous specified by rdvno (called task A below) has called the rendezvous port specified
by portid with the rendezvous condition calptn and the calling message msg.
The operations of fwd_por is described in detail as follows.
If a task is waiting to accept a rendezvous at the rendezvous port to which the rendezvous is forwarded, and if the rendezvous condition of the waiting task and that specified by calptn match, this service call establishes a rendezvous between the task andtask A. If there are more than one task waiting to accept a rendezvous, this service callcheck their rendezvous conditions one by one starting from the task at the head of the206

µITRON4.0 Specification

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accept-wait queue. The service call establishes a rendezvous with the first task thatmatches the rendezvous condition.
When a rendezvous is established, this service call assigns a rendezvous number to theestablished rendezvous and moves task A to the termination waiting state for the rendezvous. The service call also copies the calling message specified by msg andcmsgsz into the memory area specified by the accepting task, which was in theaccepting waiting state for the rendezvous. The service call then releases the task fromwaiting. The released task receives the calling message size (cmsgsz) as the return
value of the service call that caused it to wait in the accept-wait queue and the assigned
rendezvous number through rdvno.
If no tasks are waiting to accept a rendezvous at the rendezvous port to which the rendezvous is forwarded, or if none of the waiting tasks has a matching rendezvous condition, task A is placed in the call-wait queue of the rendezvous port to which therendezvous is forwarded, and is moved to the calling waiting state for the rendezvous.
The calling message specified by msg and cmsgsz is copied to the memory area
specified by task A to store the return message.
If there are already tasks in the rendezvous port’s call-wait queue, task A is placed in
the call-wait queue as described below. If the rendezvous port’s attribute has
TA_TFIFO (= 0x00) set, task A is placed at the tail of the call-wait queue. If the rendezvous port’s attribute has TA_TPRI (= 0x01) set, task A is placed in the call-wait
queue in the order of the task’s priority. If the call-wait queue contains tasks with thesame priority as task A, task A is placed after those tasks.
The maximum return message size of the rendezvous port to which the rendezvous isforwarded must be smaller than or equal to that of the rendezvous port at which the rendezvous was established. Otherwise an E_ILUSE error is returned.
When cmsgsz is larger than the maximum calling message size of the rendezvous port
to which the rendezvous is forwarded, or when cmsgsz is larger than the return message size of the rendezvous port at which the rendezvous was established, an E_PAR
error is returned. cmsgsz may be specified as 0.
A rendezvous number accepted by another task may also be specified in rdvno. In
other words, the task that invokes fwd_por and forwards the rendezvous does not necessarily correspond to the task that has accepted the rendezvous.
If the task that has called the rendezvous specified by rdvno is not in the termination
waiting state for the same rendezvous, an E_OBJ error is returned. An E_OBJ error
is also returned when the value specified by rdvno cannot be interpreted as a rendezvous number.
An E_PAR error is returned when calptn is 0.
[Supplemental Information]
Since the result of invoking fwd_por is the same as if task A has called the rendezvous

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port, the record of forwarding a rendezvous is not necessary. For this reason, a forwarded rendezvous can be forwarded again.
Since the execution of fwd_por ends immediately, the task that invokes fwd_por
never enters the WAITING state. The application can reuse the area in which the calling message was stored for other purposes after fwd_por returns because the calling
message specified by msg and cmsgsz is copied to another area during the executionof fwd_por. After fwd_por returns, the task that invoked fwd_por is detached fromthe following: the rendezvous port at which the rendezvous was established, the rendezvous port to which the rendezvous is forwarded, the forwarded rendezvous, and the
newly established rendezvous if any.
A timeout specified for tcal_por applies to the interval from the invocation of
tcal_por to the termination of the rendezvous. Therefore, if task A called a rendezvous by tcal_por, the specified timeout continues to be valid after the rendezvous isforwarded.
The rendezvous port to which the rendezvous is forwarded may be the same rendezvous port at which the rendezvous was originally established. In this case, the accepted
rendezvous is returned to the original state before it was established. However, the rendezvous pattern and the calling message are changed to those specified for fwd_por.
Even if the task that has called the rendezvous is released from the termination waiting
state for the rendezvous due to a timeout or a forced release after the rendezvous isestablished, its release would not be notified to the task that has accepted the rendezvous. In this case, an E_OBJ error is returned if the task that accepted the rendezvous
invokes fwd_por and tries to forward the rendezvous. The task can determine whether
the calling task for the rendezvous is still in the termination waiting state by invoking
ref_rdv.
Figure 4-4 illustrates a server distribution task using fwd_por.
[Differences from the µITRON3.0 Specification]
When task A is moved to the calling waiting state for a rendezvous, the calling message
specified by msg and cmsgsz is now defined to be stored in the area in which task A
stores the return message.
The handling of timeout in fwd_por has been changed according to the changed interpretation of timeout for tcal_por.
The fact that a task other than the task that has accepted the rendezvous can forward therendezvous is now clarified.
The calling message size can now be specified as 0.
The data types of calptn, rdvno, and cmsgsz have been changed from UINT to
RDVPTN, from RNO to RDVNO, and from INT to UINT, respectively.
[Rationale]
In order to reduce the number of states the system should handle, the specification does
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Client task

Server distribution task
cal_por

acp_porport

fwd_por

fwd_por
port

port

acp_por

port

acp_porServertask for
Service A

Servertask for
Service B

rpl_rdv

rpl_rdv

fwd_por

acp_porServertask for
Service C

rpl_rdv

Figure 4-4. Server Distribution Task using fwd_por
not require the record of forwarding a rendezvous. In cases where the record is necessary, the rendezvous may be called, instead of forwarded by fwd_por, using nested
cal_por.
The following states the reason why an error is returned when the maximum return
message size of the rendezvous port to which the rendezvous is forwarded is larger
than that of the rendezvous port at which the rendezvous was established. Task A must
allocate a memory area that can hold a return message of the maximum allowed size
from the rendezvous port that task A first called. If the maximum return message sizeof the rendezvous port to which the rendezvous is forwarded is larger, the return message may not fit in the allocated area.
An error is returned if cmsgsz is larger than the maximum return message size of therendezvous port at which the rendezvous was established. This is because when task A
is moved to the calling waiting state for a rendezvous, task A copies the calling message specified by msg and cmsgsz to the area it allocated for storing the return message.

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µITRON4.0 Specification

rpl_rdv

Ver. 4.00.00

Terminate Rendezvous[C Language API]ER ercd = rpl_rdv ( RDVNO rdvno, VP msg, UINT rmsgsz ) ;[Parameter]
RDVNO
VP
UINT

rdvno
msg
rmsgsz[Return Parameter]ER
ercd[Error Code]
E_PAR
E_OBJ

Rendezvous number to be terminatedStart address of the return message
Return message size (in bytes)
E_OK for normal completion or error code

Parameter error (msg or rmsgsz is invalid)
Object state error (rdvno is invalid)[Functional Description]
This service call terminates the rendezvous specified by rdvno. The start address of
the return message is specified by msg and its size in bytes is specified by rmsgsz.
Specifically, if the task which has called the rendezvous specified by rdvno is in thetermination waiting state for the rendezvous, this service call copies the return message
specified by msg and rmsgsz to the area allocated by the calling task to store thereturn message. The service call then releases the task from waiting. The released task
receives the return message size (rmsgsz) as the return value of the service call thatcaused it to wait.
If the task that has called the rendezvous specified by rdvno is not in the termination
waiting state for the same rendezvous, an E_OBJ error is returned. An E_OBJ error
is also returned when the value specified by rdvno cannot be interpreted as a rendezvous number.
A rendezvous number accepted by another task may also be specified in rdvno. In
other words, the task that invokes rpl_rdv and terminates the rendezvous does not necessarily correspond to the task that has accepted the rendezvous.
When rmsgsz is larger than the maximum return message size of the rendezvous port
to which the rendezvous was established, an E_PAR error is returned. rmsgsz may
be specified as 0.
[Supplemental Information]
Even if the task that has called the rendezvous is released from the termination waiting
state for the rendezvous due to a timeout or a forced release after the rendezvous isestablished, its release would not be notified to the task that has accepted the rendezvous. In this case, an E_OBJ error is returned if the task that accepted the rendezvous
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invokes rpl_rdv and tries to terminate the rendezvous. The task can determine
whether the calling task for the rendezvous is still in the termination waiting state by
invoking ref_rdv.
After the rendezvous is established, both the calling and accepting tasks are detachedfrom the rendezvous port. However, the maximum return message size for the rendezvous port is necessary for checking if the return message size (rmsgsz) is smaller thanor equal to the maximum size. For this reason, the maximum return message size mustbe saved in conjunction with the rendezvous. The maximum size, for example, can be
stored in the TCB of the task in the calling waiting state or in an area (such as the stackarea) that can be referenced from the TCB.
[Differences from the µITRON3.0 Specification]
The fact that a task other than the task that has accepted the rendezvous can terminate
the rendezvous is now clarified.
The return message size can now be specified as 0.
The data types of rdvno and rmsgsz have been changed from RNO to RDVNO andfrom INT to UINT, respectively.
[Rationale]
A rendezvous port ID is not passed as a parameter to rpl_rdv because the task that has
called the rendezvous is detached from the rendezvous port once the rendezvous isestablished.
When rdvno is invalid, an E_OBJ error is returned instead of an E_PAR error. Thisis because an invalid value of rdvno cannot be detected statically.

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µITRON4.0 Specification

ref_porVer. 4.00.00

Reference Rendezvous Port State[C Language API]ER ercd = ref_por ( ID porid, T_RPOR *pk_rpor ) ;[Parameter]ID
T_RPOR *porid
pk_rpor[Return Parameter]ER
ercd

ID number of the rendezvous port to be referenced
Pointer to the packet returning the rendezvous port
state
E_OK for normal completion or error code

pk_rpor includes (T_RPOR type)ID
ctskidID number of the task at the head of the call-waitqueueID
atskidID number of the task at the head of the accept-wait
queue(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (porid is invalid or unusable)
Non-existent object (specified rendezvous port is not registered)
Parameter error (pk_rpor is invalid)[Functional Description]
This service call references the state of the rendezvous port specified by porid. The
state of the rendezvous port is returned through the packet pointed to by pk_rpor.
The ID number of the task at the head of the rendezvous port’s call-wait queue isreturned through ctskid. If no tasks are waiting to call a rendezvous at the rendezvous
port, TSK_NONE (= 0) is returned instead.
The ID number of the task at the head of the rendezvous port’s accept-wait queue isreturned through atskid. If no tasks are waiting to accept a rendezvous at the rendezvous port, TSK_NONE (= 0) is returned instead.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The ID
number of the task at the head of each wait queue is now returned instead of a boolean
value indicating whether a task is waiting or not. Based on this replacement, the names
and data types of the return parameters have been changed. The order of parameters
and of return parameters has been changed.

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µITRON4.0 Specification

ref_rdv

Ver. 4.00.00

Reference Rendezvous State[C Language API]ER ercd = ref_rdv ( RDVNO rdvno, T_RRDV *pk_rrdv ) ;[Parameter]
RDVNO
T_RRDV *rdvno
pk_rrdv[Return Parameter]ER
ercd

Rendezvous number of the rendezvous to be referenced
Pointer to the packet returning the rendezvous state
E_OK for normal completion or error code

pk_rrdv includes (T_RRDV type)ID
wtskidID number of the task in the termination waiting
state for the rendezvous(Other implementation specific information may be added.)[Error Code]
E_PAR

Parameter error (pk_rrdv is invalid)[Functional Description]
This service call references the state of the rendezvous to which the rendezvous number specified by rdvno is assigned. The state of the rendezvous is returned through thepacket pointed to by pk_rrdv.
When the task that has called the rendezvous specified by rdvno is in the termination
waiting state for the same rendezvous, the ID number of the task is returned throughwtskid. If the task is not in the termination waiting state for the same rendezvous, orif the rdvno cannot be interpreted as a rendezvous number, TSK_NONE (= 0) is
returned instead.
[Supplemental Information]
When this service call invoked with a rendezvous number returns a task ID throughwtskid , rpl_rdv or fwd_por invoked with the same rendezvous number neverreturns an E_OBJ error.
[Differences from the µITRON3.0 Specification]
ref_rdv has been newly added. The ITRON2 Specification had a corresponding service call, rdv_sts.

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4.6 Memory Pool Management Functions
Memory pool management functions provide dynamic memory management by software. Memory pool management functions include fixed-sized memory pool and variable-sized memory pool.
[Supplemental Information]
The µITRON4.0 Specification does not specify functions for multiple logical memory
spaces or hardware memory management unit (MMU).

4.6.1 Fixed-Sized Memory Pools
A fixed-sized memory pool is an object for dynamically managing fixed-sized memory
blocks. The fixed-sized memory pool functions include the ability to create and delete
a fixed-sized memory pool, to acquire and release a memory block to/from afixed-sized memory pool, and to reference the state of a fixed-sized memory pool. A
fixed-sized memory pool is an object identified by an ID number. The ID number of a
fixed-sized memory pool is called the fixed-sized memory pool ID.
A fixed-sized memory pool has an associated memory area where fixed-sized memory
blocks are allocated (this is called fixed-sized memory pool area or simply memory
pool area) and an associated wait queue for acquiring a memory block. If there are no
memory blocks available, a task trying to acquire a memory block from the fixed-sized
memory pool will be in the waiting state for a fixed-sized memory block until a memory block is released. The task waiting to acquire a fixed-sized memory block is placedin the fixed-sized memory pool’s wait queue.
The following kernel configuration macro is defined for use with the fixed-sized memory pool functions:
SIZE mpfsz = TSZ_MPF ( UINT blkcnt, UINT blksz )This macro returns the total required size of the fixed-size memory pool area inbytes necessary to allocate blkcnt memory blocks each of size blksz bytes.
The following data type packets are defined for creating and referencing fixed-sized
memory pools:
typedef struct t_cmpf {ATR
mpfatr ;UINT
blkcnt ;UINT
blksz ;VP
mpf ;/* Fixed-sized memory pool attribute *//* Total number of memory blocks *//* Memory block size (in bytes) *//* Start address of the fixed-sized memory
pool area *//* Other implementation specific fields may be added. */} T_CMPF ;typedef struct t_rmpf {214

µITRON4.0 Specification
ID

Ver. 4.00.00
wtskid ;/* ID number of the task at the head of the
fixed-sized memory pool’s wait
queue */
UINT
fblkcnt ;/* Number of free memory blocks in the
fixed-sized memory pool *//* Other implementation specific fields may be added. */} T_RMPF ;The following represents the functions codes for the fixed-sized memory pool service
calls:
TFN_CRE_MPF
TFN_ACRE_MPF
TFN_DEL_MPF
TFN_GET_MPF
TFN_PGET_MPF
TFN_TGET_MPF
TFN_REL_MPF
TFN_REF_MPF

–0x45
–0xc9
–0x46
–0x49
–0x4a
–0x4b
–0x47
–0x4c

Function code of cre_mpf
Function code of acre_mpf
Function code of del_mpf
Function code of get_mpf
Function code of pget_mpf
Function code of tget_mpf
Function code of rel_mpf
Function code of ref_mpf[Standard Profile]
The Standard Profile requires support for fixed-sized memory pool functions except for
dynamic creation and deletion of a fixed-sized memory pool (cre_mpf, acre_mpf,
del_mpf) and reference of a fixed-sized memory pool state (ref_mpf).
The Standard Profile does not require TSZ_MPF to be defined.
[Supplemental Information]
When using fixed-sized memory pool functions for memory blocks of different sizes, afixed-sized memory pool should be created for each size.

215

µITRON4.0 Specification

CRE_MPF
cre_mpf
acre_mpf

Ver. 4.00.00

Create Fixed-Sized Memory Pool (Static API)[S]

Create Fixed-Sized Memory Pool
Create Fixed-Sized Memory Pool (ID Number Automatic Assignment)[Static API]
CRE_MPF ( ID mpfid, { ATR mpfatr, UINT blkcnt, UINT blksz,
VP mpf } ) ;[C Language API]ER ercd = cre_mpf ( ID mpfid, T_CMPF *pk_cmpf ) ;ER_ID mpfid = acre_mpf ( T_CMPF *pk_cmpf ) ;[Parameter]ID
T_CMPF *mpfid
pk_cmpf

ID number of the fixed-sized memory pool to becreated (except acre_mpf)
Pointer to the packet containing the fixed-sized
memory pool creation information (in CRE_MPF,
packet contents must be directly specified.)pk_cmpf includes (T_CMPF type)
ATR
mpfatrFixed-sized memory pool attributeUINT
blkcntTotal number of memory blocks
UINT
blksz
Memory block size (in bytes)
VP
mpf
Start address of the fixed-sized memory pool area
(Other implementation specific information may be added.)[Return Parameter]
cre_mpf:
ER

ercd

E_OK for normal completion or error code

acre_mpf:
ER_ID

mpfid

ID number (positive value) of the created
fixed-sized memory pool or error code

[Error Code]
E_ID
E_NOID
E_NOMEM
E_RSATR
E_PAR
E_OBJ

Invalid ID number (mpfid is invalid or unusable; only
cre_mpf)
No ID number available (there is no fixed-sized memory pool
ID assignable; only acre_mpf)
Insufficient memory (memory pool area cannot be allocated)
Reserved attribute (mpfatr is invalid or unusable)
Parameter error (pk_cmpf, blkcnt, blksz, or mpf isinvalid)Object state error (specified fixed-sized memory pool is216

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already registered; only cre_mpf)[Functional Description]
These service calls create a fixed-sized memory pool with an ID number specified by
mpfid based on the information contained in the packet pointed to by pk_cmpf.
mpfatr is the attribute of the fixed-sized memory pool. blkcnt is the total number ofmemory blocks. blksz is size of each memory block. mpf is the start address of the
fixed-sized memory pool area.
In CRE_MPF, mpfid is an integer parameter with automatic assignment. mpfatr isa preprocessor constant expression parameter.
acre_mpf assigns a fixed-sized memory pool ID from the pool of unassigned
fixed-sized memory pool IDs and returns the assigned fixed-sized memory pool ID.
mpfatr can be specified as (TA_TFIFO || TA_TPRI). If TA_TFIFO (= 0x00) is
specified, the fixed-sized memory pool’s wait queue will be in FIFO order. If
TA_TPRI (= 0x00) is specified, the fixed-sized memory pool’s wait queue will be intask priority order.
The necessary area to hold up to blkcnt memory blocks, each of size blksz bytes,
starts from mpf and is used as the fixed-size memory pool area. An application program can calculate the size of the memory pool area necessary to hold blkcnt numberof memory blocks, each of size blksz bytes, by using the TSZ_MPF macro. If mpf is
NULL (= 0), the kernel allocates the necessary memory area. When blkcnt or blksz
is specified as 0, an E_PAR error is returned.
[Standard Profile]
The Standard Profile does not require support for when other values than NULL is
specified in mpf.
[Differences from the µITRON3.0 Specification]
The start address of the memory pool area (mpf) has been added to the fixed-sized
memory pool creation information. The extended information has been removed. The
names of the parameters have been changed from mpfcnt to blkcnt and from blfsz
to blksz, respectively. In addition, their data types have been changed from INT to
UINT.
acre_mpf has been newly added.

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µITRON4.0 Specification

del_mpf

Ver. 4.00.00

Delete Fixed-Sized Memory Pool[C Language API]ER ercd = del_mpf ( ID mpfid ) ;[Parameter]
ID

mpfid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the fixed-sized memory pool to bedeleted
E_OK for normal completion or error code

Invalid ID number (mpfid is invalid or unusable)
Non-existent object (specified fixed-sized memory pool is notregistered)[Functional Description]
This service call deletes the fixed-sized memory pool specified by mpfid. If the memory pool area was allocated by the kernel, the area is released.
[Supplemental Information]See Section 3.8 for information regarding handling tasks that are waiting for a memory
block from the fixed-sized memory pool when the fixed-sized memory pool is deleted.

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µITRON4.0 Specification

get_mpf
pget_mpf
tget_mpf

Ver. 4.00.00

Acquire Fixed-Sized Memory Block[S]

Acquire Fixed-Sized Memory Block (Polling)[S]

Acquire Fixed-Sized Memory Block (with Timeout)[S][C Language API]ER ercd = get_mpf ( ID mpfid, VP *p_blk ) ;ER ercd = pget_mpf ( ID mpfid, VP *p_blk ) ;ER ercd = tget_mpf ( ID mpfid, VP *p_blk, TMO tmout ) ;[Parameter]
ID

mpfid

TMO

tmout

[Return Parameter]
ER
ercd
VP
blk
[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number or the fixed-sized memory pool fromwhich a memory block is acquired
Specified timeout (only tget_mpf)
E_OK for normal completion or error code
Start address of the acquired memory block

Invalid ID number (mpfid is invalid or unusable)
Non-existent object (specified fixed-sized memory pool is notregistered)
Parameter error (p_blk or tmout is invalid)
Forced release from waiting (accept rel_wai while waiting;
except pget_mpf)
Polling failure or timeout (except get_mpf)
Waiting object deleted (fixed-sized memory pool is deleted
while waiting; except pget_mpf)[Functional Description]
These service calls acquire a memory block from the fixed-sized memory pool specified by mpfid. The size of the memory block is specified during the creation of the
fixed-sized memory pool. The start address of the memory block is returned throughblk. Specifically, when free memory blocks are available in the memory pool area,
one of the memory blocks is selected and takes on an acquired status. If there are no
memory blocks available, the invoking task is placed in the fixed-sized memory pool’s
wait queue and is moved to the waiting state for a fixed-sized memory block.
If there are already tasks in the fixed-sized memory pool’s wait queue, the invoking
task is placed in the wait queue as described below. When the fixed-sized memory
pool’s attribute has TA_TFIFO (= 0x00) set, the invoking task is placed at the tail of
the wait queue. When the fixed-sized memory pool’s attribute has TA_TPRI (= 0x01)
set, the invoking task is placed in the wait queue in the order of the task’s priority. If
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the wait queue contains tasks with the same priority as the invoking tasks, the invoking
task is placed after those tasks.
pget_mpf is a polling service call with the same funcionality as get_mpf. tget_mpf
has the same functionality as get_mpf with an additional timeout feature. tmout canbe set to a positive number indicating a timeout duration or it can be set to TMO_POL(= 0) or TMO_FEVR (= –1).
[Supplemental Information]
The size of the acquired memory block may be larger than the memory block size thatwas specified during the creation of the fixed-sized memory pool. Since these service
calls do not clear the memory block, its contents are undefined.
tget_mpf acts the same as pget_mpf if TMO_POL is specified in tmout as long as
no context error occurs. Also, tget_mpf acts the same as get_mpf if TMO_FEVR is
specified in tmout.
[Differences from the µITRON3.0 Specification]
The names of the service calls have been changed from get_blf , pget_blf , andtget_blf to get_mpf, pget_mpf, and tget_mpf, respectively. The order of parameters and of return parameters has been changed.

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µITRON4.0 Specification

rel_mpf

Ver. 4.00.00

Release Fixed-Sized Memory Block[S][C Language API]ER ercd = rel_mpf ( ID mpfid, VP blk ) ;[Parameter]
ID
VP

mpfid
blk

ID number of the fixed-sized memory pool to which
the memory block is released
Start address of the memory block to be released

ercd

E_OK for normal completion or error code

[Return Parameter]
ER[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (mpfid is invalid or unusable)
Non-existent object (specified fixed-sized memory pool is notregistered)
Parameter error (blk is invalid, release to a different memory
pool, specified address is not the start address of a memory
block)[Functional Description]
This service call releases the memory block starting from the address specified by blk
to the fixed-sized memory pool specified by mpfid.
If there are already tasks in the fixed-sized memory pool’s wait queue, this service calllets the task at the head of the wait queue acquire the released memory block andreleases the task from waiting. The released task receives E_OK from the service callthat caused it to wait in the fixed-sized memory pool’s wait queue. It also receives thevalue specified by blk as the start address of the acquired memory block.
The fixed-sized memory pool to which the memory block is released must be the same
fixed-sized memory pool from which the memory block was acquired. Otherwise, an
E_PAR error is returned.
The start address of the memory block to be released must be the start address of an
acquired memory block returned by get_mpf, pget_mpf, or tget_mpf. In addition,
the memory block must not be a released memory block. The behavior is undefinedwhen other addresses are specified in blk. When an error should be reported, an
E_PAR error is returned.
[Differences from the µITRON3.0 Specification]
The name of the service call has been changed from rel_blf to rel_mpf. The name ofthe parameter has been changed from blf to blk.

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µITRON4.0 Specification

ref_mpf

Ver. 4.00.00

Reference Fixed-Sized Memory Pool State[C Language API]ER ercd = ref_mpf ( ID mpfid, T_RMPF *pk_rmpf ) ;[Parameter]
ID
T_RMPF *mpfid
pk_rmpf[Return Parameter]ER
ercd

ID number of the fixed-sized memory pool to bereferenced
Pointer to the packet returning the fixed-sized memory pool state
E_OK for normal completion or error code

pk_rmpf includes (T_RMPF type)ID
wtskidID number of the task at the head of the wait queue
UINT
fblkcnt
Number of free memory blocks(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (mpfid is invalid or unusable)
Non-existent object (specified fixed-sized memory pool is notregistered)
Parameter error (pk_rmpf is invalid)[Functional Description]
This service call references the state of the fixed-sized memory pool specified by
mpfid. The state of the fixed-sized memory pool is returned through the packet
pointed to by pk_rmpf.
The ID number of the task at the head of the fixed-sized memory pool’s wait queue isreturned through wtskid. If no tasks are waiting to acquire a memory block,
TSK_NONE (= 0) is returned instead.
The number of free memory blocks in the fixed-sized memory pool area is returned
through fblkcnt.
[Supplemental Information]
A fixed-sized memory pool cannot have wtskid ≠ TSK_NONE and fblkcnt ≠ 0 at
the same time.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The ID
number of the task at the head of the wait queue is now returned instead of a boolean
value indicating whether a task is waiting or not. Based on this replacement, the nameand data type of the return parameter has been changed.
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The name of the return parameter has been changed from frbcnt to fblkcnt, and its
data type has been changed from INT to UNIT. The order of parameters and of returnparameters has been changed.

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4.6.2 Variable-Sized Memory Pools
A variable-sized memory pool is an object for dynamically managing variable-sized
memory blocks. The variable-sized memory pool functions include the ability to create and delete a variable-sized memory pool, to acquire and release a memory block to/from a variable-sized memory pool, and to reference the state of a variable-sized memory pool. A variable-sized memory pool is an object identified by an ID number. The
ID number of a variable-sized memory pool is called the variable-sized memory ID.
A variable-sized memory pool has an associated memory area where variable-sized
memory blocks are allocated (this is called variable-sized memory pool area or simply
memory pool area) and an associated wait queue for acquiring a memory block. If
there are no memory blocks available, a task trying to acquire a memory block from thevariable-sized memory pool will be in the waiting state for a variable-sized memory
block until enough memory blocks are released. The task waiting to acquire a variable-sized memory block is placed in the variable-sized memory pool’s wait queue.
The following kernel configuration macro is defined for use with variable-sized memory pool functions:
SIZE mplsz = TSZ_MPL ( UINT blkcnt, UINT blksz )This macro returns an approximate size in bytes necessary to allocate blkcnt
memory blocks each of size blksz bytes.
This macro is only an estimation for determining the size of the memory pool area. It
cannot be used to determine the total required size of a memory pool area to allocate
memory blocks with different sizes. In addition, when the memory pool area becomesfragmented, the specified number of memory blocks cannot be allocated.
The following data type packets are defined for creating and referencing variable-sized
memory pools:
typedef struct t_cmpl {ATR
mplatr ;SIZE
mplsz ;/* Variable-sized memory pool attribute *//* Size of the variable-sized memory poolarea (in bytes) */VP
mpl ;/* Start address of the variable-sized
memory pool area *//* Other implementation specific fields may be added. */} T_CMPL ;typedef struct t_rmpl {IDwtskid ;SIZE

fmplsz ;/* ID number of the task at the head of thevariable-sized memory pool’s wait
queue *//* Total size of free memory blocks in thevariable-sized memory pool (inbytes) */224

µITRON4.0 Specification
UINT

Ver. 4.00.00
fblksz ;/* Maximum memory block size available(in bytes) *//* Other implementation specific fields may be added. */} T_RMPL ;The following represents the functions codes for the variable-sized memory pool service calls:
TFN_CRE_MPL
TFN_ACRE_MPL
TFN_DEL_MPL
TFN_GET_MPL
TFN_PGET_MPL
TFN_TGET_MPL
TFN_REL_MPL
TFN_REF_MPL

–0xa1
–0xca
–0xa2
–0xa5
–0xa6
–0xa7
–0xa3
–0xa8

Function code of cre_mpl
Function code of acre_mpl
Function code of del_mpl
Function code of get_mpl
Function code of pget_mpl
Function code of tget_mpl
Function code of rel_mpl
Function code of ref_mpl[Standard Profile]
The Standard Profile does not require support for variable-sized memory pool functions.
[Supplemental Information]
Tasks that are waiting for a memory block from a variable-sized memory pool will
acquire a memory block in the order that the tasks are placed in the wait queue. An
example is when task A tries to acquire 400 byte memory block from a variable-sized
memory pool and task B tries to acquire 100 byte memory block from the same variable-sized memory pool. Assume that these tasks are placed in the wait queue so thattask A is ahead of task B. A third task then releases 200 byte memory block to the variable-sized memory pool, resulting in 200 bytes of available area in the variable-sized
memory pool. Even though task B only needs 100 bytes to acquire a memory block, itcannot do so until task A has acquired a memory block. However, an implementation-specific extension can add an attribute to the variable-sized memory pool that willallow task B to acquire a memory block before task A in this example.
[Differences from the µITRON3.0 Specification]
Whether tasks should acquire memory blocks according to their order in the wait queueor according to which task can acquire a memory block first was implementation-dependent in the µITRON3.0 Specification. The µITRON4.0 Specifications has
determined the former order to be standard.

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µITRON4.0 Specification

CRE_MPL
cre_mplacre_mpl

Ver. 4.00.00

Create Variable-Sized Memory Pool (Static API)
Create Variable-Sized Memory Pool

Create Variable-Sized Memory Pool (ID Number Automatic Assignment)[Static API]
CRE_MPL ( ID mplid, { ATR mplatr, SIZE mplsz, VP mpl } ) ;[C Language API]ER ercd = cre_mpl ( ID mplid, T_CMPL *pk_cmpl ) ;ER_ID mplid = acre_mpl ( T_CMPL *pk_cmpl ) ;[Parameter]ID
T_CMPL *mplid
pk_cmplID number of the variable-sized memory pool to becreated (except acre_mpl)
Pointer to the packet containing the variable-sized
memory pool creation information (in CRE_MPL,
packet contents must be directly specified.)pk_cmpl includes (T_CMPL type)
ATR
mplatrVariable-sized memory pool attribute
SIZE
mplsz
Size of the variable-sized memory pool area (inbytes)
VP
mpl
Start address of the variable-sized memory poolarea
(Other implementation specific information may be added.)[Return Parameter]
cre_mpl:ER

ercd

E_OK for normal completion or error code

acre_mpl:
ER_ID

mplid

ID number (positive value) of the created variable-sized memory pool or error code

[Error Code]
E_ID
E_NOID
E_NOMEM
E_RSATR
E_PAR
E_OBJ

Invalid ID number (mplid is invalid or unusable; only
cre_mpl)No ID number available (there is no variable-sized memory
pool ID assignable; only acre_mpl)
Insufficient memory (memory pool area cannot be allocated)
Reserved attribute (mplatr is invalid or unusable)
Parameter error (pk_cmpl, mplsz, or mpl is invalid)
Object state error (specified variable-sized memory pool isalready registered; only cre_mpl)
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µITRON4.0 Specification

Ver. 4.00.00[Functional Description]
These service calls create a variable-sized memory pool with an ID number specified
by mplid based on the information contained in the packet pointed to by pk_cmpl.
mplatr is the attribute of the variable-sized memory pool. mplsz is the size of thevariable-sized memory pool area in bytes. mpl is the start address of the variable-sized memory pool area.
In CRE_MPL, mplid is an integer parameter with automatic assignment. mplatr isa preprocessor constant expression parameter.
acre_mpl assigns a variable-sized memory pool ID from the pool of unassigned variable-sized memory pool IDs and returns the assigned variable-sized memory pool ID.
mplatr can be specified as (TA_TFIFO || TA_TPRI). If TA_TFIFO (= 0x00) is
specified, the variable-sized memory pool’s wait queue will be in FIFO order. If
TA_TPRI (= 0x00) is specified, the variable-sized memory pool’s wait queue will be intask priority order.
The memory area starting from mpl and whose size is mplsz is used as the memory
pool area. Because the information for memory block management is also placed in
the memory pool area, the whole memory pool area cannot be used to allocate memory
blocks. An application program can estimate the size to be specified in mplsz by using
the TSZ_MPL macro. If mpl is NULL (= 0), the kernel allocates the necessary memory area in bytes specified by mplsz. When mplsz is specified as 0, an E_PAR error
is returned.
[Differences from the µITRON3.0 Specification]
The start address of the memory pool area (mpl) has been added to the variable-sized
memory pool creation information. The extended information has been removed. The
data type of mplsz has been changed from INT to SIZE.
acre_mpl has been newly added.

227

µITRON4.0 Specification

del_mplVer. 4.00.00

Delete Variable-Sized Memory Pool[C Language API]ER ercd = del_mpl ( ID mplid ) ;[Parameter]
ID

mplid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the variable-sized memory pool to bedeleted
E_OK for normal completion or error code

Invalid ID number (mplid is invalid or unusable)
Non-existent object (specified variable-sized memory pool is
not registered)[Functional Description]
This service call deletes the variable-sized memory pool specified by mplid. If thememory pool area was allocated by the kernel, the area is released.
[Supplemental Information]See Section 3.8 for information regarding handling tasks that are waiting for a memory
block from the variable-sized memory pool when the variable-sized memory pool isdeleted.

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µITRON4.0 Specification

get_mplpget_mpl
tget_mpl

Ver. 4.00.00

Acquire Variable-Sized Memory Block
Acquire Variable-Sized Memory Block (Polling)
Acquire Variable-Sized Memory Block (with Timeout)[C Language API]ER ercd = get_mpl ( ID mplid, UINT blksz, VP *p_blk ) ;ER ercd = pget_mpl ( ID mplid, UINT blksz, VP *p_blk ) ;ER ercd = tget_mpl ( ID mplid, UINT blksz, VP *p_blk,
TMO tmout ) ;[Parameter]
ID

mplid

UINT
TMO

blksz
tmout

[Return Parameter]
ER
ercd
VP
blk
[Error Code]
E_ID
E_NOEXS
E_PAR
E_RLWAIE_TMOUT
E_DLT

ID number of the variable-sized memory pool fromwhich a memory block is acquired
Memory block size to be acquired (in bytes)
Specified timeout (only tget_mpl)
E_OK for normal completion or error code
Start address of the acquired memory block

Invalid ID number (mplid is invalid or unusable)
Non-existent object (specified variable-sized memory pool is
not registered)
Parameter error (p_blk, tmout is invalid)
Forced release from waiting (accept rel_wai while waiting;
except pget_mpl)
Polling failure or timeout (except get_mpl)
Waiting object deleted (variable-sized memory pool is deleted
while waiting; except pget_mpl)[Functional Description]
These service calls acquire a memory block whose size is specified by blksz from thevariable-sized memory pool specified by mplid. The start address of the memory
block is returned through blk.
Specific actions to be performed depend on whether there is a task waiting to acquire amemory block with precedence over the invoking task. If no tasks are waiting toacquire a memory block from the variable-sized memory block, or if the variable-sized
memory pool’s attribute has TA_TPRI (= 0x01) set and the invoking task has higher
priority than all of the waiting tasks, a memory block of size blksz bytes is acquired
from the memory pool area. If the conditions are not satisfied or if the free memoryarea is insufficient for acquiring a memory block, the invoking task is placed in the229

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variable-sized memory pool’s wait queue and is moved to the waiting state for a variable-sized memory block.
If there are already tasks in the variable-sized memory pool’s wait queue, the invoking
task is placed in the wait queue as described below. When the variable-sized memory
pool’s attribute has TA_TFIFO (= 0x00) set, the invoking task is placed at the tail of
the wait queue. When the variable-sized memory pool’s attribute has TA_TPRI(= 0x01) set, the invoking task is placed in the wait queue in the order of the task’s priority. If the wait queue contains tasks with the same priority as the invoking tasks, theinvoking task is placed after those tasks.
When the first task in the wait queue has changed as the result of releasing a task in thewait queue from waiting with rel_wai, ter_tsk, or a timeout, the actions, when possible, to make the tasks acquire memory blocks starting from the new first task in thewait queue are necessary. Since the specific actions are similar to the actions to betaken after rel_mpl has released a memory block to the variable-sized memory pool,see the functional description of rel_mpl for more details. The same actions are also
necessary when the first task in the wait queue has changed as the result of changing
the priority of a task in the wait queue by chg_pri or mutex operations.
pget_mpl is a polling service call with the same funcionality as get_mpl. tget_mpl
has the same functionality as get_mpl with an additional timeout feature. tmout canbe set to a positive number indicating a timeout duration or it can be set to TMO_POL(= 0) or TMO_FEVR (= –1).
[Supplemental Information]
The size of the acquired memory block may be larger than the size specified by blksz.
Since these service calls do not clear the memory block, its contents are undefined.
tget_mpl acts the same as pget_mpl if TMO_POL is specified in tmout as long as
no context error occurs. Also, tget_mpl acts the same as get_mpl if TMO_FEVR is
specified in tmout.
[Differences from the µITRON3.0 Specification]
The names of the service calls have been changed from get_blk, pget_blk, andtget_blk to get_mpl, pget_mpl, and tget_mpl, respectively. The data type ofblksz has been changed from INT to UINT. The order of parameters and of returnparameters has been changed.

230

µITRON4.0 Specification

rel_mplVer. 4.00.00

Release Variable-Sized Memory Block[C Language API]ER ercd = rel_mpl ( ID mplid, VP blk ) ;[Parameter]
ID
VP

mplid
blk

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR

ID number of the variable-sized memory pool towhich the memory block is released
Start address of memory block to be released
E_OK for normal completion or error code

Invalid ID number (mplid is invalid or unusable)
Non-existent object (specified variable-sized memory pool is
not registered)
Parameter error (blk is invalid, release to a different memory
pool, specified address is not the start address of a memory
block)[Functional Description]
This service call release the memory block starting from the address specified by blk
to the variable-sized memory pool specified by mplid.
If there are already tasks in the variable-sized memory pool’s wait queue, this service
call checks if, as a result of releasing the memory block, the first task in the wait queue
can acquire a memory block of the requested size. If the requested size is met, the service call lets the task acquire the memory block and releases the task from waiting.
The released task receives E_OK from the service call that caused it to wait in the variable-sized memory pool’s wait queue. It also receives the start address of the acquired
memory block. When some tasks still remain in the wait queue after the release of thetask, the same actions must be repeated on the new head task in the wait queue.
The variable-sized memory pool to which the memory block is released must be thesame variable-sized memory pool from which the memory block was acquired. Otherwise, an E_PAR error is returned.
The start address of the memory block to be released must be the start address of an
acquired memory block returned by get_mpl, pget_mpl, or tget_mpl. In addition,
the memory block must not be a released memory block. The behavior is undefinedwhen other addresses are specified in blk. When an error should be reported, an
E_PAR error is returned.

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µITRON4.0 Specification

Ver. 4.00.00[Supplemental Information]
If this service call releases more than one task from waiting, the order of release corresponds with the order in which the tasks are placed in the wait queue. Therefore,among the same priority tasks moved to the runnable state, the task closer to the headof the wait queue has higher precedence.
[Differences from the µITRON3.0 Specification]
The name of the service call has been changed from rel_blk to rel_mpl.

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ref_mplVer. 4.00.00

Reference Variable-Sized Memory Pool State[C Language API]ER ercd = ref_mpl ( ID mplid, T_RMPL *pk_rmpl ) ;[Parameter]
ID
T_RMPL *mplid
pk_rmpl[Return Parameter]ER
ercd

ID number of the variable-sized memory pool to bereferenced
Pointer to the packet returning the variable-sized
memory pool state
E_OK for normal completion or error code

pk_rmpl includes (T_RMPL type)ID
wtskidID number of the task at the head of the wait queue
SIZE
fmplszTotal size of free memory blocks (in bytes)
UINT
fblkszMaximum memory block size available (in bytes)(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (mplid is invalid or unusable)
Non-existent object (specified variable-sized memory pool is
not registered)
Parameter error (pk_rmpl is invalid)[Functional Description]
This service call references the state of the variable-sized memory pool specified by
mplid. The state of the memory pool is returned through the packet pointed to by
pk_rmpl.
The ID number of the task at the head of the variable-sized memory pool’s wait queueis returned through wtskid . If no tasks are waiting to acquire a memory block,
TSK_NONE (= 0) is returned instead.
The current total size of free memory blocks in the variable-sized memory pool in
bytes is returned through fmplsz.
The size of the largest free memory block in bytes that can be acquired immediatelyfrom the variable-sized memory pool is returned through fblksz. When the size of thememory block is too large to represent with UINT type, the maximum value that can fit
in UINT type is returned through fblksz.
[Supplemental Information]
If the kernel uses dynamic memory management internally, this service call can beused as an API to reference the kernel’s dynamic memory area. Specifically, this ser233

µITRON4.0 Specification

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vice call returns the information on the kernel’s dynamic memory area when invokedwith an ID number of (–4). However, wtskid does not have a meaning in this case. In
addition, if the kernel manages more than one dynamic memory area, these can be referenced through ID numbers (–3) and (–2).
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The ID
number of the task at the head of the wait queue is now returned instead of a boolean
value indicating whether a task is waiting or not. Based on this replacement, the names
and data types of the return parameters have been changed.
The names of the return parameters have been changed from frsz to fmplsz and frommaxsz to fblksz. The data types of fmplsz and fblksz have been changed from INT
to SIZE and from INT to UINT, respectively. The order of parameters and of returnparameters has been changed.

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4.7 Time Management Functions
Time management functions provide time-dependent processing. The time management functions include system time management, cyclic handlers, alarm handlers, andoverrun handlers. Cyclic handlers, alarm handlers, and overrun handlers are generically called time event handlers.
[Supplemental Information]
The contexts and states under which time event handlers execute are summarized asfollows:• Time event handlers execute in their own independent contexts (see Section 3.5.1).
The contexts in which time event handlers execute are classified as non-task contexts(see Section 3.5.2).
• Time event handlers execute at lower precedence than the interrupt handler thatcalled isig_tim, but at higher precedence than the dispatcher (see Section 3.5.3).
• After time event handlers start, the system is in the CPU unlocked state. When
returning from time event handlers, the system must be in the CPU unlocked state(see Section 3.5.4).
• The start of and the return from time handlers do not change the dispatching state.
When the dispatching state is changed within time event handlers, the original statemust be restored before returning (see Section 3.5.5).
[Differences from the µITRON3.0 Specification]
The name cyclic handler has been changed from cyclic activation handler. Overrun
handler is a newly added feature. The delay task function (del_tsk) has been moved
from time management functions to task dependent synchronization functions.
ret_tmr has been removed (see Section 3.9).

4.7.1 System Time Management
System time management functions provide control over system time. System time
management functions include the ability to set and get the system time and to supply atime tick for updating the system time.
System time initializes to 0 when the system is started (see Section 3.7) and will be
updated every time isig_tim is invoked by the application. The amount of time added
to the system time when isig_tim is invoked is implementation-defined. The frequency of calling isig_tim from the application must be correlated with the amount oftime added to the system time. If the kernel has a mechanism of updating the systemtime, isig_tim need not be supported.
The following features depend on the system time: processing of timeouts, releasingtasks from waiting after a call to dly_tsk, and activation of cyclic handlers and alarm
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handlers. The execution order of multiple processes that start at the same system timetick is implementation-dependent.
The following kernel configuration constants are defined for use with system time management functions:
TIC_NUME
TIC_DENO

Time tick period numerator
Time tick period denominator

These constants allow the application to reference the approximate time precision of
the system time. TIC_NUME/TIC_DENO is the time tick period measured in thesame units as the system time. If the system time is not updated periodically, the constants should still be defined so that they reflect the characteristic of the system time
precision.
The following represents the function codes for the system time management service
calls:
TFN_SET_TIM
TFN_GET_TIM
TFN_ISIG_TIM

–0x4d
–0x4e
–0x7d

Function code of set_tim
Function code of get_tim
Function code of isig_tim[Standard Profile]
The Standard Profile requires support for the system time management functions.
However, if the kernel has a mechanism of updating the system time, isig_tim neednot be supported.
[Supplemental Information]
Another method to define TIC_NUME and TIC_DENO is to allow the application todefine them in the system configuration file or in header files prepared by the application. The kernel determines the period that isig_tim is invoked by the applicationfrom these constants.
[Differences from the µITRON3.0 Specification]
The name system time has been changed from system clock. The service call to supply
a time tick (isig_tim) has been newly added. This allows the kernel to be independentof timer hardware.
The recommended number of bits used to represent the value of the system time is not
specified. In the µITRON3.0 Specification it was 48 bits. Now the system is set to 0
upon initialization. In the µITRON3.0 Specification, the recommended start date forabsolute time was January 1st, 1985, 0:00 am GMT.

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µITRON4.0 Specification

set_timVer. 4.00.00[S]

Set System Time[C Language API]ER ercd = set_tim ( SYSTIM *p_systim ) ;[Parameter]
SYSTIMsystim[Return Parameter]ER
ercd[Error Code]
E_PAR

Time to set as system time
E_OK for normal completion or error code

Parameter error (p_systim or systim is invalid)[Functional Description]
This service call sets the system time to the value specified by systim.
[Supplemental Information]
Changing the system time using this service call will not change the time in the realworld when an event specified using relative time is to occur. However, the systemtime when that event occurs will change (see Section 2.1.9).
[Differences from the µITRON3.0 Specification]
The data type of the system time has been changed from SYSTIME to SYSTIM. The
parameter name in the C language API has changed from pk_tim to p_systim.
[Rationale]systim is passed through a pointer because passing the parameter value may reduce
system efficiency when SYSTIM is defined as a data structure.

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µITRON4.0 Specification

get_timVer. 4.00.00[S]

Reference System Time[C Language API]ER ercd = get_tim ( SYSTIM *p_systim ) ;[Parameter]
None[Return Parameter]
ER
ercd
SYSTIMsystim[Error Code]
E_PAR

E_OK for normal completion or error code
Current system time

Parameter error (p_systim is invalid)[Functional Description]
This service call returns the current system time through systim.
[Differences from the µITRON3.0 Specification]
The data type of the system time has been changed from SYSTIME to SYSTIM. The
parameter name in the C language API has changed from pk_tim to p_systim.

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µITRON4.0 Specification

isig_tim

Ver. 4.00.00[S]

Supply Time Tick

[C Language API]ER ercd = isig_tim ( ) ;[Parameter]
None[Return Parameter]ER
ercd

E_OK for normal completion or error code

[Error Code]No errors specific to this service call
[Functional Description]
This service call updates the system time.
[Standard Profile]
The Standard Profile does not require support for this service call if the kernel has amechanism of updating the system time.
[Supplemental Information]
This service call may start processes that depend on the system time. This does notmean that these processes must be executed within this service call. This implies thatthese processes do not necessarily complete before the service call returns.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

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4.7.2 Cyclic Handlers
A cyclic handler is a time event handler activated periodically. Cyclic handler functions include the ability to create and delete a cyclic handler, to start and stop a cyclic
handler’s operation, and to reference the state of a cyclic handler. A cyclic handler isan object identified by an ID number. The ID number of a cyclic handler is called thecyclic handler ID.
The activation cycle and activation phase are set at the creation of the cyclic handler.
The kernel determines the next time the handler will be activated based on the activation cycle and the activation phase. When the cyclic handler is created, the first activation time is calculated by adding the activation phase to the time at which the cyclic
handler was created. At the cyclic handler’s activation time, the cyclic handler is calledwith its extended information (exinf) passed as a parameter. At this time the next activation time is calculated by adding the activation cycle to the current activation time.
In addition, the next activation time may be recalculated when the cyclic handler’s
operation is started.
Generally, a cyclic handler’s activation phase is less than its activation cycle. The
behavior is implementation-dependent when the activation phase is longer than theactivation cycle.
A cyclic handler is either in an operational state or a non-operational state. When acyclic handler is in a non-operational state, the cyclic handler is not activated at its activation time. Instead, its next activation time is determined. When the service call thatstarts the operation of a cyclic handler (sta_cyc) is invoked, the cyclic handler is
moved to an operational state and its next activation time is recalculated if necessary.
When the service call that stops the operation of a cyclic handler (stp_cyc) is invoked,
the cyclic handler is moved to a non-operational state. After the creation of a cyclic
handler, the cyclic handler’s attribute determines the operational state of the cyclic handler.
The activation phase is the relative time from the time when the cyclic handler was created to the first activation time. If the cyclic handler is created through a static API, thecreation time is considered to be the system initialization time. The activation cycle is
the relative time from the last activation time to the next activation time. The last activation time may not have been the actual time of activation, but rather the last expected
activation time. An actual interval between actual activations can possibly be shorter
than the activation cycle. However, in the long term, the average actual activationinterval will correspond with the activation cycle.
The format to write a cyclic handler in the C language is shown below:
void cychdr ( VP_INT exinf ){/* Body of the cyclic handler */}240

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The following data type packets are defined for creating and referencing cyclic handlers:
typedef struct t_ccyc {ATR
cycatr ;/* Cyclic handler attribute */VP_INT
exinf ;/* Cyclic handler extended information */FP
cychdr ;/* Cyclic handler start address */RELTIM
cyctim ;/* Cyclic handler activation cycle */RELTIM
cycphs ;/* Cyclic handler activation phase *//* Other implementation specific fields may be added. */} T_CCYC ;typedef struct t_rcyc {STAT
cycstat ;/* Cyclic handler operational state */RELTIM
lefttim ;/* Time left before the next activation *//* Other implementation specific fields may be added. */} T_RCYC ;The following represents the function codes for the cyclic handler service calls:
TFN_CRE_CYC
TFN_ACRE_CYC
TFN_DEL_CYC
TFN_STA_CYC
TFN_STP_CYC
TFN_REF_CYC

–0x4f
–0xcb
–0x50
–0x51
–0x52
–0x53

Function code of cre_cyc
Function code of acre_cyc
Function code of del_cyc
Function code of sta_cyc
Function code of stp_cyc
Function code of ref_cyc[Standard Profile]
The Standard Profile requires support for cyclic handler functions except for dynamically creation and deletion of a cyclic handler (cre_cyc, acre_cyc, del_cyc) and reference of a cyclic handler state (ref_cyc).
The Standard Profile does not require support for preserving the activation phase,
which is specified by TA_PHS in the cyclic handler’s attribute.
[Supplemental Information]
When the activation phase is preserved, the activation time is determined so that thequantity (((activation time) – (creation time)) % (activation cycle)) is constant. Figure
4-5 show how the cyclic handler is activated after it is created with TA_STP specified
in its attribute and then it is moved to an operational state with sta_cyc. When theactivation phase is preserved, the activation time is always determined base on the creation time (Figure 4-5 (a)). When the activation phase is not preserved the activation
time is determined base on the time when sta_cyc is invoked (Figure 4-5 (b)).
The activation of cyclic handlers depends on the system time. Therefore, these handlers are activated at the first time tick after the activation time has passed. The activation phase is the relative time from when the cyclic handler was created. This meansthat the first activation of the cyclic handler occurs after an elapsed time equal to or
greater than the activation phase (as long as the cyclic handler is in an operational
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µITRON4.0 Specification

cre_cyc (TA_STA not specified)

activcation phase

activation cycle

Ver. 4.00.00

sta_cyc

Cyclic handler is called.

activation cycle(a) when the activation phase is preserved (TA_PHS specified)
cre_cyc (TA_STA not specified)

activcation phasesta_cyc

activation cycle

Cyclic handler is called.

activation cycle(b) when the activation phase is not preserved (TA_PHS not specified)Figure 4-5. Preserving Activation Phasestate). The activation cycle is the relative time from the last activation time. Thismeans that the n-th activation of the cyclic handler must occur after an elapsed timeequal to or greater than ((activation phase) + (activation cycle) * (n–1)) from the creation time. For example, for a system with a 10 millisecond time tick where a cyclic
handler is created through the static API with the activation phase set to 15 milliseconds and the activation cycle set to 25 milliseconds, then the activation times will be at
20, 40, 70, 90, and 120 milliseconds and so on. See Section 2.1.9 for how to handle
events specified with relative times.
This specification describes the calculation of the next activation time even when acyclic handler is in a non-operational state. This calculation can be omitted in an
implementation as long as the behavior of cyclic handlers do not change.
[Differences from the µITRON3.0 Specification]
The name cyclic handler has been changed from cyclic activation handler. Cyclic handlers are now identified by ID numbers. Cyclic handlers are now objects created by
cre_cyc rather than defined by def_cyc. The service call to delete a cyclic handler(del_cyc) has been newly added.
The service call to control the operational state of a cyclic handler (act_cyc) has been
divided into a service call that starts the operation of a handler (sta_cyc) and one thatstops the operation of a handler (stp_cyc).

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µITRON4.0 Specification

CRE_CYC
cre_cycacre_cycVer. 4.00.00

Create Cyclic Handler (Static API)[S]

Create Cyclic Handler
Create Cyclic Handler (ID Number Automatic Assignment)[Static API]
CRE_CYC ( ID cycid, { ATR cycatr, VP_INT exinf, FP cychdr,
RELTIM cyctim, RELTIM cycphs } ) ;[C Language API]ER ercd = cre_cyc ( ID cycid, T_CCYC *pk_ccyc ) ;ER_ID cycid = acre_cyc ( T_CCYC *pk_ccyc ) ;[Parameter]ID
T_CCYC *cycid
pk_ccyc

ID number of the cyclic handler to be created(except acre_cyc)
Pointer to the packet containing the cyclic handler
creation information (In CRE_CYC, the contents
must be directly specified.)pk_ccyc includes (T_CCYC type)
ATR
cycatrCyclic handler attribute
VP_INT
exinf
Cyclic handler extended information
FP
cychdrCyclic handler start address
RELTIM
cyctimCyclic handler activation cycle
RELTIM
cycphsCyclic handler activation phase(Other implementation specific information may be added.)[Return Parameter]
cre_cyc:ER

ercd

E_OK for normal completion or error code

acre_cyc:
ER_ID

cycid

ID number (positive value) of the created cyclic
handler or error code

[Error Code]
E_ID
E_NOID
E_RSATR
E_PAR
E_OBJ

Invalid ID number (cycid is invalid or unusable; only
cre_cyc)
No ID number available (there is no cyclic handler ID assignable; only acre_cyc)
Reserved attribute (cycatr is invalid or unusable)
Parameter error (pk_ccyc, cychdr, cyctim, or cycphs isinvalid)Object state error (cyclic handler is already registered; only243

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cre_cyc)[Functional Description]
These service calls create a cyclic handler with an ID number specified by cycid basedon the information contained in the packet pointed to by pk_ccyc. cycatr is theattribute of the cyclic handler. exinf is the extended information passed as a parameterto the cyclic handler when it is called. cychdr is the start address of the cyclic handler. cyctim is the activation cycle time. cycphs is the activation phase.
In CRE_CYC, cycid is an integer parameter with automatic assignment. cycatr is a
preprocessor constant expression parameter.
acre_cyc assigns a cyclic handler ID from the pool of unassigned cyclic handler IDs
and returns the assigned cyclic handler ID.
cycatr can be specified as ((TA_HLNG || TA_ASM) | [TA_STA] | [TA_PHS]). If
TA_HLNG (= 0x00) is specified, the cyclic handler is called through the C language
interface. If TA_ASM (= 0x01) is specified, the cyclic handler is called through anassembly language interface. If TA_STA (= 0x02) is specified, the handler is in an
operational state when it is created, otherwise it is in a non-operational state. If
TA_PHS (= 0x04) is specified, the next activation time is determined preserving theactivation phase when the cyclic handler is moved to an operational state. See thefunctional description of sta_cyc for the actions to be taken when a cyclic handler is
moved to an operational state.
The first activation time of the cyclic handler is the time when the service call is
invoked plus the activation phase. For the static API, the system initialization time isused as the invoking time.
When cyctim is 0, an E_PAR error is returned. The behavior of the system when thevalue of cycphs is greater than cyctim is implementation-dependent. When an error
should be reported, an E_PAR error is returned.
[Standard Profile]
The Standard Profile does not require support for when T_PHS or TA_ASM is specified in cycatr.
[Supplemental Information]
The cyclic handler activation phase (cycphs) does not have any meaning when neither
TA_STA nor TA_PHS are specified in cycatr.
[Differences from the µITRON3.0 Specification]
Cyclic handlers are now objects created by cre_cyc rather than defined by def_cyc.
The functionality for specifying the activation phase has been newly added. The activation phase (cycphs) has been added to the cyclic handler creation information. The
method for specifying the cyclic handler’s operational state after creation has beenchanged.

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The order of cycatr and exinf in the creation information packet has been exchanged.
The data type of exinf has been changed from VP to VP_INT and the data type of
cyctim has been changed from CYCTIME to RELTIM.
acre_cyc has been newly added.

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del_cycVer. 4.00.00

Delete Cyclic Handler[C Language API]ER ercd = del_cyc ( ID cycid ) ;[Parameter]
ID

cycid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the cyclic handler to be deleted
E_OK for normal completion or error code

Invalid ID number (cycid is invalid or unusable)
Non-existent object (specified cyclic handler is not registered)[Functional Description]
This service call deletes the cyclic handler specified by cycid.
[Differences from the µITRON3.0 Specification]
This service call has been newly added. In the µITRON3.0 Specification, the def_cyc
service call can be used for releasing a handler as well as defining a handler.

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µITRON4.0 Specification

sta_cycVer. 4.00.00

Start Cyclic Handler Operation[S][C Language API]ER ercd = sta_cyc ( ID cycid ) ;[Parameter]
ID

cycid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the cyclic handler operation to be
started
E_OK for normal completion or error code

Invalid ID number (cycid is invalid or unusable)
Non-existent object (specified cyclic handler is not registered)[Functional Description]
This service call moves the cyclic handler specified by cycid to an operational state.
If the handler’s attribute does not have TA_PHS (= 0x04) specified, the next activation
time is the time when sta_cyc is invoked plus the activation cycle.
If the cyclic handler is already in an operational state and TA_PHS is not specified in
the attribute, the activation time is recalculated. If the cyclic handler is already in an
operational state and TA_PHS is specified in the attribute, no action is required.
[Differences from the µITRON3.0 Specification]
The service call to control the operational state of a cyclic handler (act_cyc) has been
divided into a service call that starts the operation of a handler (sta_cyc) and one thatstops the operation of a handler (stp_cyc). In the µITRON3.0 Specification, when the
act_cyc service call is invoked with TCY_INI specified, the activation time is recalculated. A similar functionality is achieved through the use of TA_PHS.

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stp_cycVer. 4.00.00

Stop Cyclic Handler Operation[S][C Language API]ER ercd = stp_cyc ( ID cycid ) ;[Parameter]
ID

cycid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the cyclic handler operation to be
stopped
E_OK for normal completion or error code

Invalid ID number (cycid is invalid or unusable)
Non-existent object (specified cyclic handler is not registered)[Functional Description]
This service call moves the cyclic handler specified by cycid to a non-operational
state. No action is required when the specified cyclic handler is already in a non-operational state.
[Differences from the µITRON3.0 Specification]
The service call to control the operational state of a cyclic handler (act_cyc) has been
divided into a service call that starts the operation of a handler (sta_cyc) and one thatstops the operation of a handler (stp_cyc).

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ref_cycVer. 4.00.00

Reference Cyclic Handler State[C Language API]ER ercd = ref_cyc ( ID cycid, T_RCYC *pk_rcyc ) ;[Parameter]ID
T_RCYC *cycid
pk_rcyc[Return Parameter]ER
ercd

ID number of the cyclic handler to be referenced
Pointer to the packet returning the cyclic handler
state
E_OK for normal completion or error code

pk_rcyc includes (T_RCYC type)
STAT
cycstatCyclic handler operational state
RELTIM
lefttimTime left before the next activation(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (cycid is invalid or unusable)
Non-existent object (specified cyclic handler is not registered)
Parameter error (pk_rcyc is invalid)[Functional Description]
This service call references the state of the cyclic handler specified by cycid. The stateof the cyclic handler is returned through the packet pointed to by pk_rcyc.
One of the following values is returned through cycstat depending on the operational
state of the cyclic handler:
TCYC_STP
TCYC_STA

0x00
0x01

Cyclic handler is in a non-operational state
Cyclic handler is in an operational state

The amount of time remaining before the cyclic handler’s next activation time isreturned through lefttim if the cyclic handler is in an operational state. This means thetime returned is the next activation time minus the current time. The value returned
will be less than the time it will take to activate the cyclic handler. Therefore, if 0 is
returned, the cyclic handler will be activated on the next time tick. The value returned
through lefttim when the cyclic handler is a non-operational state is implementation-dependent.
[Differences from the µITRON3.0 Specification]
The extended information has been removed from the reference information. The
method to reference the operational state has been changed. The data type of lefttim
has been changed from CYCTIME to RELTIM. The order of parameters and of
return parameters has been changed.
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4.7.3 Alarm Handlers
An alarm handler is a time event handler activated at a specified time. Alarm handler
functions include the ability to create and delete an alarm handler, to start and stop an
alarm handler’s operation, and to reference the state of an alarm handler. An alarm
handler is an object identified by an ID number. The ID number of an alarm handler iscalled the alarm handler ID.
The time at which the alarm handler is activated, called the activation time of the alarm
handler, can be set for each handler. At the alarm handler’s activation time, the alarm
handler is called with its extended information (exinf) passed as a parameter.
The activation time of the alarm handler is not set when the handler is created. Therefore, the operation of the alarm handler is stopped. The service call that starts the operation of an alarm handler (sta_alm) sets the activation time relative to the time when
the service call is invoked. In addition, the alarm handler is moved to an operational
state. When the service call that stops the operation of an alarm handler (stp_alm) is
invoked, the activation time is released and the alarm handler is moved to a non-operational state. When an alarm handler is called, the activation time is released and thealarm handler is moved to a non-operational state.
The format to write an alarm handler in the C language is shown below:
void almhdr ( VP_INT exinf ){/* Body of the alarm handler */}The following data type packets are defined for creating and referencing alarm handlers:
typedef struct t_calm {ATR
almatr ;/* Alarm handler attribute */VP_INT
exinf ;/* Alarm handler extended information */FP
almhdr ; /* Alarm handler start address *//* Other implementation specific fields may be added. */} T_CALM ;typedef struct t_ralm {STAT
almstat ; /* Alarm handler operational state */RELTIM
lefttim ;/* Time left before the activation *//* Other implementation specific fields may be added. */} T_RALM ;The following represents the function codes for the alarm handler service calls:
TFN_CRE_ALM
TFN_ACRE_ALM
TFN_DEL_ALM
TFN_STA_ALM
TFN_STP_ALM

–0xa9
–0xcc
–0xaa
–0xab
–0xac

Function code of cre_alm
Function code of acre_alm
Function code of del_alm
Function code of sta_alm
Function code of stp_alm
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µITRON4.0 Specification
TFN_REF_ALM

Ver. 4.00.00–0xad

Function code of ref_alm[Standard Profile]
The Standard Profile does not require support for alarm handlers.
[Supplemental Information]
The activation of alarm handlers depends on the system time. Therefore, these handlers are activated at the first time tick after the activation time has passed. The system
must guarantee that the activation of the alarm handler occurs after an elapsed timeequal to or greater than the specified time (see Section 2.1.9).
The activation time is released when the alarm handler is called but before the alarm
handler is executed. If an implementation allows non-task contexts to invoke the service call to start the alarm handler operation, the alarm handler can reset the activation
time and move itself to an operational state.
[Differences from the µITRON3.0 Specification]
Alarm handlers are now identified by ID numbers. Alarm handlers are now objects created by cre_alm rather than defined by def_alm. The service call to delete an alarm
handler (del_alm) has been newly added.
For the case when an alarm handler is created statically, the activation time of the alarm
handler is now specified with the newly added service call (sta_alm) instead of thecreate alarm handler service call or the static API. The service call to stop the operation of a alarm handler (stp_alm) has been newly added.
The ability to set an alarm handler activation time to an absolute time has been
removed.

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CRE_ALM
cre_alm
acre_alm

Ver. 4.00.00

Create Alarm Handler (Static API)
Create Alarm Handler
Create Alarm Handler (ID Number Automatic Assignment)[Static API]
CRE_ALM ( ID almid, { ATR almatr, VP_INT exinf, FP almhdr } ) ;[C Language API]ER ercd = cre_alm ( ID almid, T_CALM *pk_calm ) ;ER_ID almid = acre_alm ( T_CALM *pk_calm ) ;[Parameter]ID
T_CALM *almid
pk_calm

ID number of the alarm handler to be created(except acre_alm)
Pointer to the packet containing the alarm handler
creation information (In CRE_ALM, the contents
must be directly specified.)

pk_calm includes (T_CALM type)
ATR
almatrAlarm handler attribute
VP_INT
exinf
Alarm handler extended information
FP
almhdrAlarm handler start address(Other implementation specific information may be added.)[Return Parameter]
cre_alm:ER

ercd

E_OK for normal completion or error code

acre_alm:
ER_ID

almid

ID number (positive value) of the created alarm
handler or error code

[Error Code]
E_ID
E_NOID
E_RSATR
E_PAR
E_OBJ

Invalid ID number (almid is invalid or unusable; only
cre_alm)
No ID number available (there is no alarm handler ID assignable; only acre_alm)
Reserved attribute (almatr is invalid or unusable)
Parameter error (pk_calm or almhdr is invalid)
Object state error (alarm handler is already registered; only
cre_alm)[Functional Description]
These service calls create an alarm handler with an ID number specified by almid
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based on the information contained in the packet pointed to by pk_calm. almatr is
the attribute of the alarm handler. exinf is the extended information passed as aparameter to the alarm handler when it is called. almhdr is the start address of thealarm handler.
In CRE_ALM, almid is an integer parameter with automatic assignment. almatr isa preprocessor constant expression parameter.
acre_alm assigns an alarm handler ID from the pool of unassigned alarm handler IDs
and returns the assigned alarm handler ID.
After the alarm handler is created, the activation time is not set and the alarm handler isin a non-operational state.
almatr can be specified as (TA_HLNG || TA_ASM). If TA_HLNG (= 0x00) is specified, the alarm handler is called through the C language interface. If TA_ASM(= 0x01) is specified, the alarm handler is called through an assembly language interface.
[Differences from the µITRON3.0 Specification]
Alarm handlers are now objects created by cre_alm rather than defined by def_alm.
For the case when an alarm handler is created statically, the activation time of the alarm
handler is not specified by the create alarm handler service call or the static API.
The order of almatr and exinf in the creation information packet has been exchanged.
The data type of exinf has been changed from VP to VP_INT.
acre_alm has been newly added.

253

µITRON4.0 Specification

del_alm

Ver. 4.00.00

Delete Alarm Handler[C Language API]ER ercd = del_alm ( ID almid ) ;[Parameter]
ID

almid

ID number of the alarm handler to be deleted[Return Parameter]ER
ercd

E_OK for normal completion or error code

[Error Code]
E_ID
E_NOEXS

Invalid ID number (almid is invalid or unusable)
Non-existent object (specified alarm handler is not registered)[Functional Description]
This service call deletes the alarm handler specified by almid.
[Supplemental Information]
If the alarm handler is in an operational state, the activation time is released and thealarm handler is moved to a non-operational state.
[Differences from the µITRON3.0 Specification]
This service call has been newly added. In the µITRON3.0 Specification, the def_alm
service call can be used for releasing a handler as well as defining a handler.

254

µITRON4.0 Specification

sta_alm

Ver. 4.00.00

Start Alarm Handler Operation[C Language API]ER ercd = sta_alm ( ID almid, RELTIM almtim ) ;[Parameter]ID
RELTIMalmid
almtim[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR

ID number of the alarm handler operation to be
startedActivation time of the alarm handler (relative time)
E_OK for normal completion or error code

Invalid ID number (almid is invalid or unusable)
Non-existent object (specified alarm handler is not registered)
Parameter error (almtim is invalid)[Functional Description]
This service call sets the activation time of the alarm handler specified by almid. The
activation time is set to the time when the service call is invoked plus the relative time
specified by almtim. The alarm handler is also moved to an operational state.
If the alarm handler is already in an operational state, the previous activation time isreleased and a new activation time is set.
almtim is the relative time from when this service call is invoked to the activation
time of the alarm handler.
[Differences from the µITRON3.0 Specification]
This service call has been newly added. The µITRON3.0 Specification allowed
def_alm to set the activation time of an alarm handler.

255

µITRON4.0 Specification

stp_alm

Ver. 4.00.00

Stop Alarm Handler Operation[C Language API]ER ercd = stp_alm ( ID almid ) ;[Parameter]
ID

almid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the alarm handler operation to be
stopped
E_OK for normal completion or error code

Invalid ID number (almid is invalid or unusable)
Non-existent object (specified alarm handler is not registered)[Functional Description]
This service call releases the activation time of the alarm handler specified by almid
and moves the alarm handler to a non-operational state. If the alarm handler is alreadyin a non-operational state, no action is required.
[Differences from the µITRON3.0 Specification]
This service call has been newly added. The µITRON3.0 specification did not allow an
alarm handler to be stopped by any other means than releasing the registration of thealarm handler.

256

µITRON4.0 Specification

ref_alm

Ver. 4.00.00

Reference Alarm Handler State[C Language API]ER ercd = ref_alm ( ID almid, T_RALM *pk_ralm ) ;[Parameter]ID
T_RALM *almid
pk_ralm[Return Parameter]ER
ercd

ID number of the alarm handler to be referenced
Pointer to the packet returning the alarm handler
state
E_OK for normal completion or error code

pk_ralm includes (T_RALM type)
STAT
almstatAlarm handler operational state
RELTIM
lefttimTime left before the activation(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (almid is invalid or unusable)
Non-existent object (specified alarm handler is not registered)
Parameter error (pk_ralm is invalid)[Functional Description]
This service call references the state of the alarm handler specified by almid. The
state of the alarm handler is returned through the packet pointed to by pk_ralm.
One of the following values will be returned through almstat depending on the operational state of the alarm handler:
TALM_STPTALM_STA

0x00
0x01

Alarm handler is in a non-operational state
Alarm handler is in an operational state

The amount of time remaining before the alarm handler’s activation time is returned
through lefttim if the alarm handler is in an operational state. This means the time
returned is the activation time minus the current time. The value returned will be lessthan the time it will take to activate the alarm handler. Therefore, if 0 is returned, thealarm handler will be activated on the next time tick. The value returned throughlefttim when the alarm handler is a non-operational state is implementation-dependent.
[Differences from the µITRON3.0 Specification]
The alarm handler operational state (almstat) has been added to the reference information. The extended information has been removed from the reference information.
The data type of lefttim has been changed from ALMTIME to RELTIM. The orderof the parameters and of the return parameters has been changed.
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Ver. 4.00.00

4.7.4 Overrun Handler
The overrun handler is a time event handler activated when a task has been executed by
the processor longer than a specified amount of time. Overrun handler functions
include the ability to define the overrun handler, to start and stop the overrun handler’s
operation, and to reference the state of the overrun handler.
The amount of time used to determine the activation condition, called the processor
time limit, can be specified for each task. Once a task has a processor time limit set,
the kernel keeps track of the accumulated processor time consumed by the task, called
the processor time used, until the consumed time exceeds the time limit. Once thisoccurs, the overrun handler is called. Because only one overrun handler can be definedfor the whole system, the task ID number (tskid) and the task’s extended information(exinf) are passed as parameters to the overrun handler.
The task’s processor time limit is not set when the task is created. When the service
call to start the overrun handler operation (sta_ovr) is invoked for a specified task, theprocessor time limit is set for the task. In addition, the processor time used for the task
is cleared to 0. Once the service call to stop the overrun handler operation (stp_ovr) is
invoked for a specified task, the processor time limit for the task is released. The processor time limit for a task is also released when the overrun handler is called for thetask or when the task is terminated.
The processor time used by a task includes the time consumed by the task, by the task’s
exception handling routine, and by all service calls invoked by the task. On the other
hand, the time consumed by the other tasks, by their exception handling routines, andby all the service calls they invoke are not included in the processor time used by thetask. The decision to include the time for task dispatching and for interrupt processing
is implementation-dependent. In addition, the accuracy of the measured processor timeused is implementation-dependent. Nevertheless, the overrun handler is activated only
when the processor time used exceeds the specified processor time limit.
The following data type is used within the overrun handler functions:OVRTIM

Processor time (unsigned integer, unit of time is implementation-defined)

The format to write an overrun handler in the C language is shown below:
void ovrhdr ( ID tskid, VP_INT exinf ){/* Body of the overrun handler */}The following data type packets are defined for defining and referencing overrun handlers:
typedef struct t_dovr {ATR
ovratr ;FP
ovrhdr ;/* Overrun handler attribute *//* Overrun handler start address */258

µITRON4.0 Specification

Ver. 4.00.00/* Other implementation specific fields may be added. */} T_DOVR ;typedef struct t_rovr {STAT
ovrstat ;/* Overrun handler operational state */OVRTIM leftotm ;/* Remaining processor time *//* Other implementation specific fields may be added. */} T_ROVR ;The following represents the function codes for the overrun handler service calls:
TFN_DEF_OVR
TFN_STA_OVR
TFN_STP_OVR
TFN_REF_OVR

–0xb1
–0xb2
–0xb3
–0xb4

Function code of def_ovr
Function code of sta_ovr
Function code of stp_ovr
Function code of ref_ovr[Standard Profile]
The Standard Profile does not require support for the overrun handler.
[Supplemental Information]
The activation of the overrun handler does not depend on the system time. This implies
the handler is not necessarily called synchronously with the time tick. Implementations may call the overrun handler synchronously with the time tick.
A task’s processor time limit is released when the handler is called but before the overrun handler is executed. If an implementation allows non-task contexts to invoke theservice call to start the overrun handler operation, the overrun handler can reset the processor time limit for the task that causes the overrun handler’s activation.
The overrun handler can raise a task’s exception. Then, the task’s exception handlingroutine is started by the kernel within the task’s context to handle the overrun situation.
[Differences from the µITRON3.0 Specification]
Overrun handler is a newly added feature.

259

µITRON4.0 Specification

DEF_OVR
def_ovr

Ver. 4.00.00

Define Overrun Handler (Static API)
Define Overrun Handler[Static API]DEF_OVR ( { ATR ovratr, FP ovrhdr } ) ;[C Language API]ER ercd = def_ovr ( T_DOVR *pk_dovr ) ;[Parameter]
T_DOVR *pk_dovr

Pointer to the packet containing the overrun handler
definition information (in DEF_OVR, the contents
must be directly specified.)

pk_dovr includes (T_DOVR type)
ATR
ovratrOverrun handler attributeFP
ovrhdrOverrun handler start address(Other implementation specific information may be added.)[Return Parameter]ER
ercd[Error Code]
E_RSATR
E_PAR

E_OK for normal completion or error code

Reserved attribute (ovratr is invalid or unusable)
Parameter error (pk_dovr or ovrhdr is invalid)[Functional Description]
This service call defines the overrun handler based on the information contained in thepacket pointed to by pk_dovr. ovratr is the attribute of the overrun handler. ovrhdr
is the start address of the overrun handler.
In DEF_OVR, ovratr is a preprocessor constant expression parameter.
If pk_dovr is NULL (= 0), the overrun handler currently defined is released and theoverrun handler becomes undefined. At this time, the processor time limits for all tasks
are also released. When a new overrun handler is defined over top of an old one, theold one is released and the new one takes its place. Under this condition, the processor
time limits for the tasks are not released.
ovratr can be specified as (TA_HLNG || TA_ASM). If TA_HLNG (= 0x00) is specified, the overrun handler is called through the C language interface. If TA_ASM(= 0x01) is specified, the overrun handler is called through an assembly language interface.
[Rationale]
The reason why the processor time limit is released for a task when the definition of thehandler is released is to ensure that there is no processor time limit set while the over260

µITRON4.0 Specification

Ver. 4.00.00

run handler is undefined.

261

µITRON4.0 Specification

sta_ovr

Ver. 4.00.00

Start Overrun Handler Operation[C Language API]ER ercd = sta_ovr ( ID tskid, OVRTIM ovrtim ) ;[Parameter]ID
OVRTIMtskid
ovrtim[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_PAR
E_OBJ

ID number of the task where the overrun handler
should start operation
Processor time limit for the task to be set
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Parameter error (ovrtim is invalid)
Object state error (overrun handler is not defined)[Functional Description]
This service call starts the operation of the overrun handler for the task specified bytskid. It also sets the processor time limit for the task as specified by ovrtim. In
addition, the processor time used by the task is cleared to 0.
Even if the task already has a processor time limit set, the processor time limit will bereset to the new value and the processor time used will be cleared to 0.
If tskid is TSK_SELF (= 0), the task that invoked the service call will be the target
task.

262

µITRON4.0 Specification

stp_ovr

Ver. 4.00.00

Stop Overrun Handler Operation[C Language API]ER ercd = stp_ovr ( ID tskid ) ;[Parameter]
ID

tskid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS
E_OBJ

ID number of the task on which the overrun handler
should stop operation
E_OK for normal completion or error code

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)Object state error (overrun handler is not defined)[Functional Description]
This service call stops the operation of the overrun handler for the task specified bytskid by releasing the processor time limit for the task. If the specified task does nothave a processor time limit set, no action is required.
If tskid is TSK_SELF (= 0), the task that invoked the service call will be the target
task.

263

µITRON4.0 Specification

ref_ovr

Ver. 4.00.00

Reference Overrun Handler State[C Language API]ER ercd = ref_ovr ( ID tskid, T_ROVR *pk_rovr ) ;[Parameter]ID
T_ROVR *tskid
pk_rovr[Return Parameter]ER
ercd

ID number of the task for which the overrun handler’s state should be referenced
Pointer to the packet returning the overrun handler
state
E_OK for normal completion or error code

pk_rovr includes (T_ROVR type)
STAT
ovrstatOverrun handler operational stateOVRTIM
leftotm
Remaining processor time
(Other implementation specific information may be added.)[Error Code]
E_ID
E_NOEXS
E_PAR
E_OBJ

Invalid ID number (tskid is invalid or unusable)
Non-existent object (specified task is not registered)
Parameter error (pk_rovr is invalid)
Object state error (overrun handler is not defined)[Functional Description]
This service call references the state of the overrun handler for the task specified bytskid. The state of the overrun handler is returned through the packet pointed to by
pk_rovr.
The operational state of the overrun handler is returned through ovrstat. One of thefollowing values is returned depending on whether the processor time limit has been
set for the task:
TOVR_STPTOVR_STA

0x00
0x01

Processor time limit is not set
Processor time limit is set

The processor time remaining until the overrun handler is called for the specified task
is returned through leftotm if the processor time limit is set for the specified task.
This means the value returned is the processor time limit minus the processor timeused. The value returned will be less than the actual remaining processor time which
can be consumed by the task until the overrun handler is called. Therefore, 0 can be
returned through leftotm if this service call is invoked just before the overrun handler iscalled. The value returned through leftotm when the processor time limit is not set forthe specified task is implementation-dependent.

264µITRON4.0 Specification

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If tskid is TSK_SELF (= 0), the task that invoked the service call will be the target
task.

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µITRON4.0 Specification

Ver. 4.00.00

4.8 System State Management Functions
System state management functions provide control of and reference to the various system states. System state management functions include the ability to rotate task precedence, to reference the ID of the task in the RUNNING state, to lock and unlock theCPU, to enable and disable dispatching, and to reference the context and the system
state.
The following data type packet is defined for referencing system state:typedef struct t_rsys {/* Implementation specific fields */} T_RSYS ;The following represents the function codes for the system state management service
calls:
TFN_ROT_RDQ
TFN_IROT_RDQ
TFN_GET_TID
TFN_IGET_TID
TFN_LOC_CPU
TFN_ILOC_CPU
TFN_UNL_CPU
TFN_IUNL_CPU
TFN_DIS_DSP
TFN_ENA_DSP
TFN_SNS_CTX
TFN_SNS_LOC
TFN_SNS_DSP
TFN_SNS_DPN
TFN_REF_SYS

–0x55
–0x79
–0x56
–0x7a
–0x59
–0x7b
–0x5a
–0x7c
–0x5b
–0x5c
–0x5d
–0x5e
–0x5f
–0x60
–0x61

Function code of rot_rdq
Function code of irot_rdq
Function code of get_tid
Function code of iget_tid
Function code of loc_cpu
Function code of iloc_cpu
Function code of unl_cpu
Function code of iunl_cpu
Function code of dis_dsp
Function code of ena_dsp
Function code of sns_ctx
Function code of sns_loc
Function code of sns_dsp
Function code of sns_dpn
Function code of ref_sys[Standard Profile]
The Standard Profile requires support for system state management functions except
for the reference of the system state (ref_sys).
[Differences from the µITRON3.0 Specification]
The category of system state management functions has been newly added.

266

µITRON4.0 Specification

rot_rdq
irot_rdq

Ver. 4.00.00[S]

Rotate Task Precedence[S][C Language API]ER ercd = rot_rdq ( PRI tskpri ) ;ER ercd = irot_rdq ( PRI tskpri ) ;[Parameter]
PRI

tskpri[Return Parameter]ER
ercd[Error Code]
E_PAR

Priority of the tasks whose precedence is rotated
E_OK for normal completion or error code

Parameter error (tskpri is invalid)[Functional Description]
These service calls rotate the precedence of the tasks with the priority specified by
tskpri. In other words, the task with the highest precedence of all the runnable tasks
with the specified priority will have the lowest precedence among the tasks with thesame priority after the precedence rotation.
If tskpri is TPRI_SELF (= 0), the base priority of the invoking task becomes the target priority. An E_PAR error is returned if TPRI_SELF is specified when the service
call is invoked from non-task contexts.
[Supplemental Information]
Round-robin scheduling can be achieved by invoking this service call periodically. No
action is required if there is a single task at the target priority or no tasks at the target
priority (no error is reported).
When the service call is invoked with the current priority of the invoking task as thetarget priority while in the dispatching enabled state, the invoking task’s precedence
becomes the lowest among the tasks with the same priority. This means the invoking
task may yield it execution privilege to another task. While in the dispatching disabledstate, the task with the highest precedence among the tasks with the same priority may
not necessarily be the running task. Therefore, the invoking task’s precedence may not
become the lowest among the tasks with the same priority using this yield method. The
yield method can be realized by invoking the service call with TPRI_SELF specified
for tskpri when the current priority of the invoking task equals its base priority, as isalways the case when mutex functions are not used.
[Differences from the µITRON3.0 Specification]
The ability to rotate the tasks precedence at the running task’s priority from non-task
contexts has been removed. Therefore, TPRI_RUN has been changed to267

µITRON4.0 Specification

Ver. 4.00.00

TPRI_SELF. TPRI_SELF now specifies the base priority of the invoking task due tothe introduction of mutex functions.

268

µITRON4.0 Specification

get_tid
iget_tid

Ver. 4.00.00

Reference Task ID in the RUNNING State

[S]
[S]

[C Language API]ER ercd = get_tid ( ID *p_tskid ) ;ER ercd = iget_tid ( ID *p_tskid ) ;[Parameter]
None[Return Parameter]
ER
ercd
ID
tskid

E_OK for normal completion or error code
ID number of the task in the RUNNING state[Error Code]No errors specific to this service call
[Functional Description]
These service calls reference the ID number of the task in the RUNNING state (thiscorresponds to the invoking task when the service call is invoked from task contexts)
and return the task ID through tskid. If no task is in the RUNNING state when theservice call is invoked from non-task contexts, TSK_NONE (= 0) is returned instead.
[Supplemental Information]
Some kernel implementations employ an idle task that runs when no application tasks
are runnable. When the service call is invoked for such a kernel implementation while
an idle task is in the RUNNING state, TSK_NONE is returned instead of the ID number of the idle task.
[Differences from the µITRON3.0 Specification]
This service call has been changed from returning the invoking task ID to returning thetask ID of the task in the RUNNING state. As a result, the behavior upon invoking thisservice call from non-task contexts has been changed.
[Rationale]
The reason why tskid is not returned through the return value of the service call isbecause negative task ID numbers can be supported.

269

µITRON4.0 Specification

loc_cpu
iloc_cpu

Ver. 4.00.00[S]

Lock the CPU[S][C Language API]ER ercd = loc_cpu ( ) ;ER ercd = iloc_cpu ( ) ;[Parameter]
None[Return Parameter]ER
ercd

E_OK for normal completion or error code

[Error Code]No errors specific to this service call
[Functional Description]
These service calls transition the system to the CPU locked state. If the system is in the
CPU locked state, no action is required.
[Supplemental Information]
The system is released from the CPU locked state when unl_cpu or iunl_cpu is
invoked once, even if multiple calls of loc_cpu or iloc_cpu have been made. Therefore, if a pair of loc_cpu or iloc_cpu and unl_cpu or iunl_cpu need to be nested,
the following method may be required:{
BOOL cpu_locked = sns_loc ( ) ;if ( !cpu_locked )loc_cpu ( ) ;/* work to do in the CPU locked state */if ( !cpu_locked )unl_cpu ( ) ;}[Differences from the µITRON3.0 Specification]
The meaning of the CPU locked state has been changed (see Section 3.5.4). In addition, the service call may now be invoked from non-task contexts.

270

µITRON4.0 Specification

unl_cpu
iunl_cpu

Ver. 4.00.00[S]

Unlock the CPU[S][C Language API]ER ercd = unl_cpu ( ) ;ER ercd = iunl_cpu ( ) ;[Parameter]
None[Return Parameter]ER
ercd

E_OK for normal completion or error code

[Error Code]No errors specific to this service call
[Functional Description]
These service calls transition the system to the CPU unlocked state. If the system is in
the CPU unlocked state, no action is required.
[Differences from the µITRON3.0 Specification]
The meaning of the CPU unlocked state has been changed (see Section 3.5.4). Now,
invoking this service call does not necessarily transition the system to the dispatchingenabled state. In addition, the service call may now be invoked from non-task contexts.

271

µITRON4.0 Specification

dis_dspVer. 4.00.00[S]

Disable Dispatching[C Language API]ER ercd = dis_dsp ( ) ;[Parameter]
None[Return Parameter]ER
ercd

E_OK for normal completion or error code

[Error Code]No errors specific to this service call
[Functional Description]
This service call transitions the system to the dispatching disabled state. If the system
is in the dispatching disabled state, no action is required.
[Supplemental Information]
The system is released from the dispatching disabled state when ena_dsp is invoked
once, even if multiple calls of dis_dsp have been made. Therefore, if a pair of
dis_dsp and ena_dsp need to be nested, the following method may be required:{
BOOL dispatch_disabled = sns_dsp ( ) ;if ( !dispatch_disabled )dis_dsp ( ) ;/* work to do in the dispatching disabled state */if ( !dispatch_disabled )ena_dsp ( ) ;}[Differences from the µITRON3.0 Specification]
The meaning of the dispatching state has been changed (see Section 3.5.5).

272

µITRON4.0 Specification

ena_dspVer. 4.00.00[S]

Enable Dispatching[C Language API]ER ercd = ena_dsp ( ) ;[Parameter]
None[Return Parameter]ER
ercd

E_OK for normal completion or error code

[Error Code]No errors specific to this service call
[Functional Description]
This service call transitions the system to the dispatching enabled state. If the system isin the dispatching enabled state, no action is required.
[Differences from the µITRON3.0 Specification]
The meaning of the dispatching state has been changed (see Section 3.5.5).

273

µITRON4.0 Specification

sns_ctx

Ver. 4.00.00[S]

Reference Contexts[C Language API]BOOL state = sns_ctx ( ) ;[Parameter]
None[Return Parameter]
BOOL
state

Context[Functional Description]
This service call returns TRUE if invoked from non-task contexts and returns FALSE
if invoked from task contexts.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

274

µITRON4.0 Specification

sns_locVer. 4.00.00[S]

Reference CPU State[C Language API]BOOL state = sns_loc ( ) ;[Parameter]
None[Return Parameter]
BOOL
state

CPU state[Functional Description]
This service call returns TRUE if the system is in the CPU locked state and returns
FALSE if the system is in the CPU unlocked state.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

275

µITRON4.0 Specification

sns_dspVer. 4.00.00

Reference Dispatching State[S][C Language API]BOOL state = sns_dsp ( ) ;[Parameter]
None[Return Parameter]
BOOL
state

Dispatching state[Functional Description]
This service call returns TRUE if the system is in the dispatching disabled state andreturns FALSE if the system is in the dispatching enabled state.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

276

µITRON4.0 Specification

sns_dpnVer. 4.00.00

Reference Dispatch Pending State[S][C Language API]BOOL state = sns_dpn ( ) ;[Parameter]
None[Return Parameter]
BOOL
state

Dispatch pending state[Functional Description]
This service call returns TRUE if the system is in the dispatch pending state andreturns FALSE in any other states. In other words, it returns TRUE, while a processing unit with higher precedence than the dispatcher is executing, while in the CPU
locked state, or while in the dispatching disabled state.
[Supplemental Information]
If the system is in the condition where this service call returns FALSE, those service
calls which possibly put the invoking task into the WAITING state may be invoked.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

277

µITRON4.0 Specification

ref_sysVer. 4.00.00

Reference System State[C Language API]ER ercd = ref_sys ( T_RSYS *pk_rsys ) ;[Parameter]
T_RSYS *pk_rsys[Return Parameter]ER
ercd

Pointer to the packet returning the system state
E_OK for normal completion or error code

pk_rsys includes (T_RSYS type)(Implementation-specific information)[Error Code]
E_PAR

Parameter error (pk_rsys is invalid)[Functional Description]
This service call references the system state and returns it through the packet pointed toby pk_rsys. The specific information referenced is implementation-defined.
[Supplemental Information]
Possible information that may be referenced by this service call includes: states which
can be referenced by other reference service calls (get_tid , sns_ctx , sns_loc ,sns_dsp, sns_dpn), priority of the task in the RUNNING state, interrupt enabled or
disabled state, interrupt mask, processor execution mode, and other information
depending on the target processor’s architecture.
[Differences from the µITRON3.0 Specification]
In the µITRON4.0 Specification, the information returned by the reference service calls( sns_ctx , sns_loc , sns_dsp ) replace the information returned by ref_sys(sysstat) in the µITRON3.0 Specification.

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Ver. 4.00.00

4.9 Interrupt Management Functions
Interrupt management functions provide management for interrupt handlers and forinterrupt service routines started by external interrupts. The interrupt management
functions include ability to define an interrupt handler, to create and delete an interrupt
service routine, to reference the state of an interrupt service routine, to disable andenable an interrupt, and to change and reference the interrupt mask. An interrupt service routine is an object identified by an ID number. The ID number of an interrupt
service routine is called the interrupt service routine ID.
The following data types are used for interrupt management functions:
INHNO
INTNO
IXXXX

Interrupt handler number
Interrupt number
Interrupt mask

The XXXX portion of the interrupt mask data type is implementation-defined andshould be an appropriate character string for the target processor’s architecture.
The format to write an interrupt handler is implementation-defined.
When calling an interrupt service routine, the extended information (exinf) of theinterrupt service routine is passed as a parameter. The format to write an interrupt service routine in the C language is shown below:
void isr ( VP_INT exinf ){/* Body of the interrupt service routine */}The following data type packets are defined for defining interrupt handlers and for creating and referencing interrupt service routines:
typedef struct t_dinh {ATR
inhatr ;/* Interrupt handler attribute */FP
inthdr ;/* Interrupt handler start address *//* Other implementation specific fields may be added. */} T_DINH ;typedef struct t_cisr {ATR
isratr ;VP_INT
exinf ;/* Interrupt service routine attribute *//* Interrupt service routine extended
information */INTNO
intno ;/* Interrupt number to which the interrupt
service routine is to be attached */FP
isr ;/* Interrupt service routine start sddress *//* Other implementation specific fields may be added. */} T_CISR ;typedef struct t_risr {/* Implementation-specific fields */} T_RISR ;279

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The following represents the function codes for the interrupt management service calls:
TFN_DEF_INH
TFN_CRE_ISR
TFN_ACRE_ISR
TFN_DEL_ISR
TFN_REF_ISR
TFN_DIS_INT
TFN_ENA_INTTFN_CHG_IXX
TFN_GET_IXX

–0x65
–0x66
–0xcd
–0x67
–0x68
–0x69
–0x6a
–0x6b
–0x6c

Function code of def_inh
Function code of cre_isr
Function code of acre_isr
Function code of del_isr
Function code of ref_isr
Function code of dis_int
Function code of ena_int
Function code of chg_ixx
Function code of get_ixx[Standard Profile]
The Standard Profile requires support for the static API to define an interrupt handler(DEF_INH). If the implementation supports the static API that attaches an interrupt
service routine to the kernel (ATT_ISR), the implementation does not have to support
DEF_INH.
[Supplemental Information]
The contexts and states under which interrupt handlers execute are summarized as follows:• Interrupt handlers execute in their own independent contexts (see Section 3.5.1).
The contexts in which interrupt handlers execute are classified as non-task contexts(see Section 3.5.2).
• Interrupt handlers execute at higher precedence than the dispatcher (see Section
3.5.3).
• After interrupt handlers start, whether the system is in the CPU locked state or in the
CPU unlocked state is implementation-dependent. However, the implementationmust provide a means to unlock the CPU in an interrupt service routine as well as ameans to correctly return from the interrupt handler after unlocking the CPU (seeSection 3.5.4).
• The start of and the return from interrupt handlers do not change the dispatchingstate. When the dispatching state is changed within interrupt handlers, the originalstate must be restored before returning (see Section 3.5.5).
The contexts and states under which interrupt service routines execute are summarized
as follows:• Interrupt service routines execute in their own independent contexts (see Section
3.5.1). The contexts in which interrupt service routines execute are classified as
non-task contexts (see Section 3.5.2).
• Interrupt service routines execute at higher precedence than the dispatcher (see Section 3.5.3).
• After interrupt service routines start, the system is in the CPU unlocked state. When280

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returning from interrupt service routines, the system must be in the CPU unlocked
state (see Section 3.5.4).
• The start of and the return from interrupt service routines do not change the dispatching state. When the dispatching state is changed within interrupt service routines, the original state must be restored before returning (see Section 3.5.5).
[Differences from the µITRON3.0 Specification]
loc_cpu and unl_cpu are now classified as system state management functions.
ret_int and ret_wup have been removed (see Section 3.9).
The data type of the parameter and the return parameter for an interrupt mask has beenchanged from UINT to a newly added data type IXXXX.

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µITRON4.0 Specification

DEF_INH
def_inh

Ver. 4.00.00

Define Interrupt Handler (Static API)[S]

Define Interrupt Handler[Static API]DEF_INH ( INHNO inhno, { ATR inhatr, FP inthdr } ) ;[C Language API]ER ercd = def_inh ( INHNO inhno, T_DINH *pk_dinh ) ;[Parameter]
INHNO
T_DINH *inhno
pk_dinh

Interrupt handler number to be defined
Pointer to the packet containing the interrupt handler definition information (in DEF_INH, packet
contents must be directly specified.)

pk_dinh includes (T_DINH type)
ATR
inhatrInterrupt handler attributeFP
inthdrInterrupt handler start address(Other implementation specific information may be added.)[Return Parameter]ER
ercd[Error Code]
E_RSATR
E_PAR

E_OK for normal completion or error code

Reserved attribute (inhatr is invalid or unusable)
Parameter error (inhno, pk_dinh, or inthdr is invalid)[Functional Description]
This service call assigns an interrupt handler to the interrupt handler number specified
by inhno based on the information contained in the packet pointed to by pk_dinh.
inhatr is the interrupt handler attribute. inthdr is the start address of the interrupt
handler.
In DEF_INH, inhno is an integer parameter without automatic assignment. inhatr
is a preprocessor constant expression parameter.
The specific meaning of inhno is implementation-defined, but it corresponds to theprocessor’s interrupt vector number in typical implementations. If a processor does nothave interrupt vectors, only one interrupt handler number may be available.
If pk_dinh is NULL (= 0), the interrupt handler currently defined is released. When a
new interrupt handler is defined over top of an old one, the old one is released and the
new takes its place.
The possible values and meanings of inhatr are implementation-defined.

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Ver. 4.00.00[Standard Profile]
The Standard Profile does not require support for DEF_INH if the implementation
supports ATT_ISR.
[Differences from the µITRON3.0 Specification]
The abbreviation of interrupt handler has been changed from int to inh. Therefore,
the name of this service call has been changed from def_int to def_inh. The possible
values and meanings of inhatr are now left to the implementation.

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ATT_ISR
cre_isr
acre_isr

Ver. 4.00.00

Attach Interrupt Service Routine (Static API)
Create Interrupt Service Routine
Create Interrupt Service Routine (ID Number Automatic Assignment)[Static API]
ATT_ISR ( { ATR isratr, VP_INT exinf, INTNO intno, FP isr } ) ;[C Language API]ER ercd = cre_isr ( ID isrid, T_CISR *pk_cisr ) ;ER_ID isrid = acre_isr ( T_CISR *pk_cisr ) ;[Parameter]ID
T_CISR *isrid
pk_cisr

ID number of the interrupt service routine to be created (only cre_isr)
Pointer to the packet containing the interrupt service
routine creation information (in ATT_ISR, packet
contents must be directly specified.)

pk_cisr includes (T_CISR type)
ATR
isratrInterrupt service routine attribute
VP_INT
exinf
Interrupt service routine extended information
INTNO
intno
Interrupt number to which the interrupt service routine is to be attachedFP
isrInterrupt service routine start address(Other implementation specific information may be added.)[Return Parameter]
cre_isr:ER

ercd

E_OK for normal completion or error code

acre_isr:
ER_ID

isrid

ID number (positive value) of the created interrupt
service routine or error code

[Error Code]
E_ID
E_NOID
E_RSATR
E_PAR
E_OBJ

Invalid ID number (isrid is invalid or unusable; only
cre_isr)
No ID number available (there is no interrupt service routine
ID assignable; only acre_isr)
Reserved attribute (isratr is invalid or unusable)
Parameter error (pk_cisr, intno, or isr is invalid)
Object state error (interrupt service routine is already registered; only cre_isr)284

µITRON4.0 Specification

Ver. 4.00.00[Functional Description]
These service calls create an interrupt service routine with an ID number specified byisrid based on the information contained in the packet pointed to by pk_cisr. isratr
is the attribute of the interrupt service routine. exinf is the extended information
passed as a parameter to the interrupt service routine when it is called. intno is thenumber of the interrupt associated with the interrupt service routine. isr is the start
address of interrupt service routine.
ATT_ISR is used to attach an interrupt service routine without assigning isrid. Theinterrupt service routines specified in this way have no ID numbers. In ATT_ISR,
isratr is a preprocessor constant expression parameter. intno is an integer parameter
without automatic assignment.
acre_isr assigns an interrupt service routine ID from the pool of unassigned interrupt
service routine IDs and returns the assigned interrupt service routine ID.
isratr can be specified as (TA_HLNG || TA_ASM). If TA_HLNG (= 0x00) is specified, the interrupt service routine is called through the C language interface. If
TA_ASM (= 0x01) is specified, the interrupt service routine is called through anassembly language interface.
[Standard Profile]
The Standard Profile does not require support for DEF_INH if the implementation
supports ATT_ISR. In this case, the Standard Profile does not require support forwhen TA_ASM is specified in isratr.
[Supplemental Information]
Multiple interrupt service routines may be attached to the same interrupt number. See
Section 3.3.2 for information on how to handle multiple interrupt service routines
attached to the same interrupt number.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

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del_isrVer. 4.00.00

Delete Interrupt Service Routine[C Language API]ER ercd = del_isr ( ID isrid ) ;[Parameter]
ID

isrid

[Return Parameter]ER
ercd[Error Code]
E_ID
E_NOEXS

ID number of the interrupt service routine to bedeleted
E_OK for normal completion or error code

Invalid ID number (isrid is invalid or unusable)
Non-existent object (specified interrupt service routine is notregistered)[Functional Description]
This service all deletes the interrupt service routine specified by isrid.
[Supplemental Information]
Interrupt service routines attached through ATT_ISR cannot be deleted with this service call because they do not have ID numbers.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

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ref_isrVer. 4.00.00

Reference Interrupt Service Routine State[C Language API]ER ercd = ref_isr ( ID isrid, T_RISR *pk_risr ) ;[Parameter]ID
T_RISR *isrid
pk_risr[Return Parameter]ER
ercd

ID number of the interrupt service routine to be referenced
Pointer a packet returning the interrupt service routine state
E_OK for normal completion or error code

pk_risr includes (T_RISR type)(Implementation-specific information)[Error Code]
E_ID
E_NOEXS
E_PAR

Invalid ID number (isrid is invalid or unusable)
Non-existent object (specified interrupt service routine is notregistered)
Parameter error (pk_risr is invalid)[Functional Description]
The service call references the state of the interrupt service routine specified by isrid.
The state of the interrupt service routine is returned through the packet pointed to by
pk_risr. The specific information returned is implementation-defined.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

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dis_int

Ver. 4.00.00

Disable Interrupt[C Language API]ER ercd = dis_int ( INTNO intno ) ;[Parameter]
INTNO

intno

[Return Parameter]ER
ercd[Error Code]
E_PAR

Interrupt number to be disabled
E_OK for normal completion or error code

Parameter error (intno is invalid)[Functional Description]
This service call disables the interrupt specified by intno. The specific meaning of
intno is implementation-defined. In typical implementations, intno corresponds tothe interrupt request line to the IRC.
[Supplemental Information]
This service call is intended to control the IRC. This service call does not transition thesystem to the CPU locked state nor does it transition the system to the dispatching disabled state. Therefore, dispatching still occurs even if all interrupts are disabled due tothis service call. In addition, if interrupts are disabled, they remain disabled after task
dispatching.
[Differences from the µITRON3.0 Specification]
Because this service call is intended to control the IRC, the meaning of intno isdefined more strictly than in the µITRON3.0 Specification. The data type of intno has
been changed from UINT to INTNO.

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µITRON4.0 Specification

ena_int

Ver. 4.00.00

Enable Interrupt[C Language API]ER ercd = ena_int ( INTNO intno ) ;[Parameter]
INTNO

intno

[Return Parameter]ER
ercd[Error Code]
E_PAR

Interrupt number to be enabled
E_OK for normal completion or error code

Parameter error (intno is invalid)[Functional Description]
This service call enables the interrupt specified by intno. The specific meaning of
intno is implementation-defined. In typical implementations, intno corresponds tothe interrupt request line to the IRC.
[Supplemental Information]
This service call is intended to control the IRC. This service call does not transition thesystem to the CPU unlocked state nor does it transition the system to the dispatchingenabled state. Therefore, this service call does not necessarily result in a state whereinterrupts will be accepted by the processor.
[Differences from the µITRON3.0 Specification]
Because this service call is intended to control the IRC, the meaning of intno isdefined more strictly than in the µITRON3.0 Specification. The data type of intno has
been changed from UINT to INTNO.

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µITRON4.0 Specification

chg_ixx

Ver. 4.00.00

Change Interrupt Mask

[C Language API]ER ercd = chg_ixx ( IXXXX ixxxx ) ;[Parameter]
IXXXX

ixxxx

[Return Parameter]ER
ercd[Error Code]
E_PAR

Interrupt mask desired
E_OK for normal completion or error code

Parameter error (ixxxx is invalid)[Functional Description]
This service call changes the processor’s interrupt mask (also referred to as interrupt
level or interrupt priority) to the value specified by ixxxx.
The xx portion of the service call name and the xxxx portion of the parameter nameare implementation-defined and should be appropriate character strings for the target
processor’s architecture.
Depending on the value specified by ixxxx, this service call may cause the transition
between the CPU locked state and the CPU unlocked state and/or the transition
between the dispatching disabled state and the dispatching enabled state. The valuecausing these transitions and the transition caused by this service call are implementation-defined.
[Supplemental Information]
In implementations where the CPU state is managed with the interrupt mask, changing
the interrupt mask may cause the transition between the CPU states or the transition
between the dispatching states. In implementations where these states are managed by
a combination of the interrupt mask and a variable, the variable’s value must be
updated to reflect the change in the interrupt mask.
[Differences from the µITRON3.0 Specification]
The data type for ixxxx has been change from UINT to IXXXX.

290

µITRON4.0 Specification

get_ixx

Ver. 4.00.00

Reference Interrupt Mask

[C Language API]ER ercd = get_ixx ( IXXXX *p_ixxxx ) ;[Parameter]
None[Return Parameter]
ER
ercd
IXXXX
ixxxx
[Error Code]
E_PAR

E_OK for normal completion or error code
Current interrupt mask

Parameter error (p_ixxxx is invalid)[Functional Description]
This service call references the processor’s interrupt mask (also referred to as interrupt
level or interrupt priority) and returns it through ixxxx.
The xx portion of the service call name and the xxxx portion of the parameter nameare implementation-defined and should be appropriate character strings for the target
processor’s architecture.
[Differences from the µITRON3.0 Specification]
The name of this service call has been changed from ref_ixx to get_ixx. The data
type for ixxxx has been change from UINT to IXXXX.

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4.10 Service Call Management Functions
Service call management functions provide definition and invocation of extended service calls. The ability to invoke extended service calls may also be used to invoke standard service calls.
An extended service call is a function that allows the invocation of another module
when the entire system is not linked to a single module. When an extended service callis invoked, the extended service call routine defined by the application is called.
The format to write an extended service call routine in the C language is shown below:
ER_UINT svcrtn ( VP_INT par1, VP_INT par2, ...){/* Body of the extended service call routine */}Only the necessary parameters for the extended service call routine (par1, par2, andso on) may be specified. There may be an implementation-defined limit on the numberof parameters for extended service calls. However, at least one parameter must be supported.
The following data type packets are used for defining extended service calls:
typedef struct t_dsvc {ATR
svcatr ;FP
svcrtn ;/* Extended service call attribute *//* Extended service call routine start
address *//* Other implementation specific fields may be added. */} T_DSVC ;The following represents the function codes for service call management service calls.
cal_svc has no function code.
TFN_DEF_SVC–0x6d

Function code of def_svc[Standard Profile]
The Standard Profile does not require support for service call management functions.
[Supplemental Information]
The contexts and states under which extended service call routines execute are summarized as follows:• An extended service call routine executes in its own independent context determinedby the extended service call and by the context from which the extended service callis invoked (see Section 3.5.1). The context in which an extended service call routine
executes is classified as task contexts when the invoking context is classified as task
contexts. It is classified as non-task contexts when the invoking context is classified
as non-task contexts (See Section 3.5.2).
• The precedence of extended service call routines is higher than the precedence of the292

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processing unit that invokes the extended service calls and is lower than the precedence of any processing unit that has a higher precedence than the invoking processing unit (see Section 3.5.3).
• The start of and the return from extended service call routines do not change theCPU state and the dispatching state (See Sections 3.5.4 and 3.5.5).
• Executing extended service call routines with task exceptions disabled is implementation-defined (see Section 4.3).
[Differences from the µITRON3.0 Specification]
The category of service call management functions has been newly added.
The terms extended SVC and extended SVC handler have been changed to extended
service call and extended service call routine, respectively. The contexts and states
under which extended service call routines execute is more strictly defined compared tothe µITRON3.0 Specification.

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µITRON4.0 Specification

DEF_SVC
def_svc

Ver. 4.00.00

Define Extended Service Call (Static API)
Define Extended Service Call

[Static API]DEF_SVC ( FN fncd, { ATR svcatr, FP svcrtn } ) ;[C Language API]ER ercd = def_svc ( FN fncd, T_DSVC *pk_dsvc ) ;[Parameter]
FN
T_DSVC *fncd
pk_dsvc

Function code of the extended service call to be
definedPointer to the packet containing the extended service call definition information (in DEF_SVC ,packet contents must be directly specified.)

pk_dsvc includes (T_DSVC type)
ATR
svcatrExtended service call attributeFP
svcrtnExtended service call routine start address(Other implementation specific information may be added.)[Return Parameter]ER
ercd[Error Code]
E_RSATR
E_PAR

E_OK for normal completion or error code

Reserved attribute (svcatr is invalid or unusable)
Parameter error (fncd, pk_dsvc, or svcatr is invalid)[Functional Description]
This service call defines an extended service call for the function code specified by
fncd based on the information contained in the packet pointed to by pk_dsvc.
svcatr is the attribute of the extended service call. svcrtn is the start address of theextended service call routine.
In DEF_SVC, fncd is an integer parameter without automatic assignment. svcatr isa preprocessor constant expression parameter.
This service call and this static API can define an extended service call with a positive
value of fncd. If a negative value is specified in fncd, an E_PAR error is reported.
If pk_dsvc is NULL (= 0), the extended service call currently defined is released andthe extended service call becomes undefined. When a new extended service call isdefined over top of an old one, the old one is released and the new takes its place.
svcatr can be specified as (TA_HLNG || TA_ASM). If TA_HLNG (= 0x00) is specified, the extended service call routine is called through the C language interface. If
TA_ASM (= 0x01) is specified, the extended service call routine is called through an294

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assembly language interface.
[Differences from the µITRON3.0 Specification]
The name of the parameter has been changed from svchdr to svcrtn.

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µITRON4.0 Specification

cal_svc

Ver. 4.00.00

Invoke Service Call

[C Language API]ER_UINT ercd = cal_svc ( FN fncd, VP_INT par1, VP_INT par2,...) ;[Parameter]FN
VP_INT
VP_INT
...

fncd
par1
par2
...

[Return Parameter]
ER_UINT ercd
[Error Code]
E_RSFN

Function code of the service call to be invoked
The first parameter of the service call
The second parameter of the service call(up to the necessary number of parameters)
The service call’s return value

Reserved function code (fncd is invalid or unusable)[Functional Description]
This service call invokes the service call specified by fncd with the parameters par1,
par2, and so on, and returns the return value of the invoked service call.
There may be an implementation-defined limit greater than or equal to 1 on the numberof parameters that can be passed to the service call. If the service call’s parameters are
not of VP_INT type, this service call converts the parameters to the appropriate datatypes while preserving their values. If the service call’s return value is of ER, BOOL,
or ER_BOOL type, this service call converts the return value to ER_UINT type while
preserving its value.
In addition to an extended service call, allowing this service call to invoke a standard
service call is implementation-defined. If this service call cannot invoke a standard service call, it returns an E_RSFN error.
[Supplemental Information]
Standard service calls are distinguished from extended service calls because the former
have negative function codes. Since cal_svc does not have a function code, cal_svc
cannot be used to invoke itself.
[Differences from the µITRON3.0 Specification]
This service call has been newly added.

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4.11 System Configuration Management Functions
System configuration management functions include the ability to define a CPU exception handler, to reference the system configuration and version information, and to
define an initialization routine. The initialization routine executes during system initialization. See Section 3.7 for the timing and contexts of initialization routine execution.
The following data types are used for system configuration management functions:
EXCNO

CPU exception handler number

The format to write a CPU exception handler is implementation-defined.
When calling an initialization routine, the extended information (exinf) of the initialization routine is passed as a parameter. The format to write an initialization routine in
the C language is shown below:
void inirtn ( VP_INT exinf ){/* Body of the initialization routine */}The following data type packets are defined for defining CPU exception handlers andfor referencing the configuration and version information.
typedef struct t_dexc {ATR
excatr ;/* CPU exception handler attribute */FP
exchdr ;/* CPU exception handler start address *//* Other implementation specific fields may be added. */} T_DEXC ;typedef struct t_rcfg {/* Implementation specific fields */} T_RCFG ;typedef struct t_rver {UHmaker ;UH
prid ;UH
spver ;UHUH

prver ;
prno[4] ;/* Kernel maker’s code *//* Identification number of the kernel *//* Version number of the ITRON
Specification *//* Version number of the kernel *//* Management information of the kernel
product */} T_RVER ;The following represents the function codes for the system configuration management
service calls:
TFN_DEF_EXC
TFN_REF_CFG
TFN_REF_VER

–0x6e
–0x6f
–0x70

Function code of def_exc
Function code of ref_cfg
Function code of ref_ver297

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Ver. 4.00.00[Standard Profile]
The Standard Profile requires support for the static API defining an CPU exception
handler (DEF_EXC) and the static API defining an initialization routine (ATT_INI).
[Supplemental Information]
The contexts and states under which CPU exception handlers execute are summarized
as follows:• The service calls that can be invoked from within CPU exception handlers are implementation-defined (see Section 3.4.2).
• A CPU exception handler executes in its own independent context determined by the
CPU exception and by the context in which the CPU exception occurred (see Section 3.5.1). When a CPU exception occurs in task contexts, whether the CPU exception handler executes in task contexts or in non-task contexts is
implementation-defined. When a CPU exception occurs in non-task contexts, theCPU exception handler executes in non-task contexts (see Section 3.5.2).
• The precedence of CPU exception handlers is higher than the precedence of the processing unit where the CPU exception occurs and higher than the precedence of thedispatcher (see Section 3.5.3).
• The start of and the return from CPU exception handlers do not change the CPU
state and the dispatching state. When the CPU state or the dispatching state ischanged in CPU exception handlers, they should be returned to their previous states
before returning from the CPU exception handlers (see Sections 3.5.4 and 3.5.5).

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µITRON4.0 Specification

DEF_EXC
def_exc

Ver. 4.00.00

Define CPU Exception Handler (Static API)[S]

Define CPU Exception Handler[Static API]DEF_EXC ( EXCNO excno, { ATR excatr, FP exchdr } ) ;[C Language API]ER ercd = def_exc ( EXCNO excno, T_DEXC *pk_dexc ) ;[Parameter]
EXCNO
T_DEXC *excno
pk_dexc

CPU exception handler number to be defined
Pointer to the packet containing the CPU exception
handler definition information (in DEF_EXC ,packet contents must be directly specified.)

pk_dexc includes (T_DEXC type)
ATR
excatrCPU exception handler attributeFP
exchdrCPU exception handler start address(Other implementation specific information may be added.)[Return Parameter]ER
ercd[Error Code]
E_RSATR
E_PAR

E_OK for normal completion or error code

Reserved attribute (excatr is invalid or unusable)
Parameter error (excno, pk_dexc, and exchdr is invalid)[Functional Description]
This service call assigns a CPU exception handler to the CPU exception handler number specified by excno based on the information contained in the packet pointed to by
pk_dexc. excatr is the attribute of CPU exception handler attribute. exchdr is thestart address of the CPU exception handler.
In DEF_EXC, excno is an integer parameter without automatic assignment. excatr
is a preprocessor constant expression parameter.
The specific meaning of excno is implementation-defined, but it corresponds to theprocessor’s exception in typical implementations.
If pk_dexc is NULL (= 0), the CPU exception handler currently defined is released.
When a new CPU exception handler is defined over top of an old one, the old one isreleased and the new takes its place.
The possible values and meanings of excatr are implementation-defined.
[Differences from the µITRON3.0 Specification]
This service call is now specified for defining a CPU exception handler. The object

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number for identifying a CPU exception handler is now the CPU exception handler
number (excno) of EXCNO type. The possible values and meanings of excatr are
now left to the implementation.

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µITRON4.0 Specification

ref_cfg

Ver. 4.00.00

Reference Configuration Information[C Language API]ER ercd = ref_cfg ( T_RCFG *pk_rcfg ) ;[Parameter]
T_RCFG *pk_rcfg[Return Parameter]ER
ercd

Pointer to the packet returning the configuration
information
E_OK for normal completion or error code

pk_rcfg includes (T_RCFG type)(Implementation-specific information)[Error Code]
E_PAR

Parameter error (pk_rcfg is invalid)[Functional Description]
This service call references the static information and configuration information of thesystem. The information is returned through the packet pointed to by pk_rcfg. The
specific information referenced is implementation-defined.
[Supplemental Information]
Possible information that may be referenced by this service call includes: the kernel
configuration constants, the range of ID numbers for each object, overview of thememory map, available memory size, information on peripheral chips and I/O devices,and time unit and precision of the data types to specify the time.

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µITRON4.0 Specification

ref_verVer. 4.00.00

Reference Version Information[C Language API]ER ercd = ref_ver ( T_RVER *pk_rver ) ;[Parameter]
T_RVER *pk_rver[Return Parameter]ER
ercd

Pointer to the packet returning the version information
E_OK for normal completion or error code

pk_rver includes (T_RVER type)UH
maker
Kernel maker’s codeUH
prid
Identification number of the kernelUH
spver
Version number of the ITRON SpecificationUH
prver
Version number of the kernelUHprno[4]
Management information of the kernel product[Error Code]
E_PAR

Parameter error (pk_rver is invalid)[Functional Description]
This service call references the version information of the kernel. The information isreturned through the packet pointed to by pk_rver. Specifically, the following information can be referenced.
maker is the code that represents the kernel maker. See Section 5.4 for definitions ofmaker codes.
prid is the number for identifying the kernel. The kernel maker can assign values toprid. A particular kernel implementation should be uniquely identified by the combination of maker and prid codes.
The upper four bits of spver identify the type of the TRON Specification, and thelower 12 bits indicate the version number of the specification. The upper four bits ofspver are assigned as follows:
0x0
0x1
0x2
0x3
0x5
0x6

Common specification for TRON (such as TAD)ITRON Specifications (ITRON1, ITRON2)BTRON Specifications
CTRON SpecificationsµITRON Specifications (µITRON2.0, µITRON3.0, µITRON4.0)µBTRON Specifications

The lower 12 bits of spver represent the upper 3 digits of the specification version
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binary coded decimal (BCD) format and each digit is 4 bit long. Version numbers fordraft specifications or specifications under discussion can include an alphabet letter. In
this case, the letter is interpreted as a hexadecimal number. See Section 5.3 for further
description on version numbers of the ITRON Specification.
prver is the version number of the particular kernel implementation. The kernelmaker can assign values to prver.
prno is a return parameter that may contain the kernel product’s management information, product number, and others. The kernel maker determines its definition.
[Supplemental Information]
As an example, the value of spver for a kernel conformant to the µITRON4.0 Specification Ver.4.02.10 is 0x5402, and its value for a kernel conformant to Ver. 4.A1.01 is
0x54A1. This example shows that a newer version of the specification does not always
have a larger value of spver when a draft specification is involved.
The returned information except prno can be referenced with the kernel configuration
macros: TKERNEL_MAKER , TKERNEL_PRID , TKERNEL_SPVER , and
TKERNEL_PRVER.
[Differences from the µITRON3.0 Specification]
The name of the service call has been changed from get_ver to ref_ver. Referencing
the CPU information and the variation descriptor have been removed. The specification of the prver format has been removed. The name of the return parameter has beenchanged from id to prid.
[Rationale]
The values stored in spver include only the upper 3 digits of the specification version
number and do not include the remaining digits. This is because the remaining digits
only refer to the notation of the specification and not the contents.

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ATT_INI

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Attach Initialization Routine (Static API)[S]

[Static API]
ATT_INI ( { ATR iniatr, VP_INT exinf, FP inirtn } ) ;[Parameter]
ATR
iniatrInitialization routine attribute
VP_INT
exinf
Initialization routine extended information
FP
inirtnInitialization routine start address(Other implementation specific information may be added.)[Functional Description]
This static API registers an initialization routine based on the specified parameters.
iniatr is the attribute of the initialization routine. exinf is the extended information
passed as a parameter to the initialization routine. inirtn is the start address of the initialization routine.
In ATT_INI, iniatr is a preprocessor constant expression parameter.
The registered initialization routine is executed as a part of the processing of the static
APIs during system initialization. See Section 3.7 for a detailed description of this process.
iniatr can be specified as (TA_HLNG || TA_ASM). If TA_HLNG (= 0x00) is specified, the initialization routine is called through the C language interface. If TA_ASM(= 0x01) is specified, the initialization routine is called through an assembly language
interface.
[Standard Profile]
The Standard Profile does not require support for when TA_ASM is specified ininiatr.
[Supplemental Information]
The system configuration file can include more than one ATT_INI. See Section 3.7 forthe execution order of the initialization routines when more than one ATT_INI are
described.
[Differences from the µITRON3.0 Specification]
This static API has been newly added.

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Chapter 5 Additional Specifications
5.1 The Specification Requirements for theµITRON4.0 Specification
5.1.1 Basic Concept
The µITRON Specifications are specifications which are based on a loose standardization concept. It emphasizes applicability to a wide range of hardwares and applications
rather than portability of application programs, and aims at standardization for the education of software engineers. Therefore, as long as the OS specification meets the minimum requirements of a real-time kernel, the realization of the functionality defined inthis specification and the addition of extended functionalities are left to the implementation.
Specifically, the following conditions must be satisfied for the implementation of theµITRON4.0 Specification.
(a) It must have the minimum functionalities that are required to satisfy theµITRON4.0 Specification (see Section 5.1.2).
(b) If it contains functionalities similar to those described in the µITRON4.0 Specification, the functionality specifications must match the µITRON4.0 Specification.
However, if the implementation does not provide a configurator, conforming to thestatic API specification of the µITRON4.0 Specification is not necessary.
(c) If it contains functionalities not specified by the µITRON4.0 Specification, thefunctionality specifications must satisfy the conditions for implementation-dependent extensions specified by the µITRON4.0 Specification. However, if the implementation supports several sets of APIs, this condition is not applied to sets of APIs
other than the µITRON4.0 Specification APIs.
If the implementation provides subsetting of service call functionalities or functionality
restrictions, or if it has special implementation functions that are not specified by theµITRON4.0 Specification, the product manual must contain the description of theimplementation for clarification.
The profile rule defines the minimum function requirements that must be satisfied by
the kernel for the portability of application programs that are written in a high-level
language. In order for an implementation based on the µITRON4.0 Specification to
conform to a certain profile rule, it must have all the functionalities specified by the
profile, and it must agree with all the rules related to the profile. It can contain functionalities that are not included by the profile and implementation-specific extensions.
However, application programs that are written to operate using only the functionalities
included in the profile must operate without modification.
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Moreover, when embedding the implemented kernel to an application, embedding only
the functions needed by the application is possible.
[Standard Profile]
The Standard Profile is one of the profile specifications of the µITRON4.0 Specification.
[Supplemental Information]
The conditions under which an implementation satisfies the µITRON4.0 Specification
is illustrated by the following example. If the implementation has semaphore functions, the names and functionalities of the service calls, the types, orders, and names ofthe parameters and return parameters, and the types and names of main error codes
must all agree with the semaphore functions that are specified by the µITRON4.0 Specification. In this case, subsetting of service call functions is permitted at the cost of
portability of application programs. If the implementation adds a functionality that is
not specified by the µITRON4.0 Specification (like counting semaphores with priority
inheritance), the functionality definition is freely decided by the implementation.
Moreover, in situations where subsets or implementation-specific extensions are made,adding and/or deleting parameters and return parameters is permitted.
The conditions of this section do not specify a kernel configured for a particular application. When a kernel conforming to the Standard Profile is embedded to an application, the kernel functionalities may be limited to those functions needed by theapplication and the range of ID numbers and priorities may be limited.

5.1.2 Minimum Required Functionalities
The minimum functionalities that are required to satisfy the µITRON4.0 Specification
are as follows:(a) Creation of tasks. The task must at least be able to be in the RUNNING state, the
READY state, and the DORMANT state.
(b) Task scheduling conforming to the µITRON4.0 Specification scheduling rule.
However, restricting the number of tasks to one for each priority level or restricting
the priority level to only one is allowed.
(c) Registration of interrupt handlers (or interrupt service routines).
(d) A method to activate tasks (changing the state from the DORMANT state to the
READY state) from tasks and interrupt handlers (or interrupt service routines).
(e) A method for a task to terminate itself (changing the state from the READY state to
the DORMANT state).
[Supplemental Information]
As an example, the minimum functionalities above can be satisfied if the implementation provides the service calls and static APIs below, and if its task scheduling rule fol306

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lows the specification.
CRE_TSK
act_tsk / iact_tsk
ext_tsk
DEF_INH

create task (static API)
activate task
terminate invoking task
define interrupt handler (static API)In this case, defining an interrupt handler (DEF_INH) can be replaced by attaching aninterrupt service routine (ATT_ISR). If a configurator is not provided, providing
equivalent methods with the static APIs instead of the static APIs conforming to thespecification is sufficient. Also act_tsk and iact_tsk do not have to support queuingof activation requests. ext_tsk can be replaced by a return from the main routine.
[Differences from the µITRON3.0 Specification]
The minimum set of states for a task is changed from the RUNNING state, the READY
state, and the WAITING state to the RUNNING state, the READY state, and the DORMANT state. The service calls required to be supported (level R) is not defined.

5.1.3 Extension of the µITRON4.0 Specification
When adding implementation-specific service calls to realize a new functionality
which is not specified by the µITRON4.0 Specification, a “v” must be added in front of
the name of the new service call. The names of the static API for implementation-specific functions are also based on this rule. However, the names for implementation-specific service calls that can be called from non-task contexts are exceptions tothis rule (see Section 3.6.3). The value of the function code for any implementation-specific service call must be within the range provided.
When adding implementation-specific main error codes, the form of the name must be
EV_XXXXX and the value of the main error code must be defined within the range
provided. Also if there are implementation-specific data types, constants (except forerror codes), and/or macros defined, identifying those that are not defined by theµITRON4.0 Specification by inserting a “V” into the name is recommended.
In the µITRON4.0 Specification, the constants that specify the object attributes and service call operational modes are assigned values that can be expressed in 8 bits. Also
the constants that express the object states are assigned 8-bit values, with a few exceptions. The lower 8-bit values of the parameters or return parameters are reserved for
future extensions of the ITRON Specifications. When assigning bit values to theimplementation-specific constants for those parameters and return parameters, the bit
values that cannot be used are the bits which are used by the constants defined by thisspecification and the reserved lowest 8 bits. The remaining values in the upper 8 bits
should be used.
Also if there are rules that specify methods for implementation-specific extensions,such as the packet for object registration information and object reference information,
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these rules must be followed.

5.2 Automotive Control Profile
The Automotive Control Profile of the µITRON4.0 Specification is one of theµITRON4.0 Specification profile rules and is mainly targeted at automotive control
applications. In order to realize the goal of reducing kernel overhead and memory
usage, a subsetting of the specification functions and additional functions for reducing
memory consumption are provided.
Compared to the Standard Profile, the Automotive Control Profile does not need to support the following functionalities:• Service calls with timeouts• Wait queues in task priority order• The SUSPENDED state• Task exception handling functions• Mailboxes• Fixed-sized memory pools• Some other service calls
In order to reduce the memory usage, restricted task functions are added. Restrictedtasks are tasks whose functionalities are restricted compared to conventional tasks. Aslong as the application does not depend on an E_NOSPT error returned whenrestricted functions are used, the application should behave the same way if therestricted tasks are replaced with conventional tasks. In this sense, the Automotive
Control Profiles have a lower compatibility to the Standard Profile even if restrictedtask functions are added.

5.2.1 Restricted Tasks
By restricting some functionalities of tasks, a restricted task can share the same stackspace with other restricted tasks. This reduces the memory area required for task stack.
A restricted task differs from a conventional task as follows:• A restricted task can not enter the WAITING state.
When a restricted task invokes a service call that might enter the WAITING state,
the behavior is undefined. When an error should be reported, an E_NOSPT error isreturned.
• The priority of a restricted task cannot be changed.
The behavior of changing a restricted task’s priority by invoking chg_pri is undefined. When an error should be reported, an E_NOSPT error is returned.
• A restricted task cannot be terminated by a service call.

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A restricted task can only be terminated by returning from the task’s main routine.
The behavior when a restricted task terminate itself by invoking ext_tsk and the
behavior when a restricted task is forcibly terminated through ter_tsk are undefined. When an error should be reported, an E_NOSPT error is returned.
Whether the task is restricted or not is determined by the task attribute specified duringtask creation. Specifically, the task will be a restricted task if the task is created by
specifying TA_RSTR (= 0x04) in the task attribute.
[Supplemental Information]
Specifying the task stack size, which is included in the task creation information, isalso valid for a restricted task. For example, if the same stack area is shared by several
restricted tasks of the same priority, setting the maximum value of each task’s stacksize to the size of the stack area allocated by the kernel is necessary. Like the Standard
Profile, the Automotive Control Profile does not require support for when other values
than NULL are specified as the start address of a task stack space.

5.2.2 Functionalities Included in the Automotive Control Profile
All the functionalities of the Automotive Control Profile except for the restricted task
functions are included in the Standard Profile. The Automotive Control Profile must
support the following static APIs and service calls.
(1) Task management functions
CRE_TSK
act_tsk / iact_tsk
can_act
ext_tsk
ter_tsk
chg_priget_pricreate task (static API)
activate task
cancel task activation requests
terminate invoking task
terminate taskchange task priority
reference task priority(2) Task dependent synchronization functions
slp_tsk
put task to sleep
wup_tsk / iwup_tsk
wakeup task
can_wupcancel task wakeup requests
rel_wai / irel_wai
release task from waiting(4) Synchronization and communication functions
Semaphores
CRE_SEM
sig_sem / isig_sem
wai_sem
pol_semcreate semaphore (static API)
release semaphore resource
acquire semaphore resource
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Eventflags
CRE_FLG
set_flg / iset_flg
clr_flg
wai_flg
pol_flg

create eventflag (static API)set eventflag
clear eventflag
wait for eventflag
wait for eventflag (polling)

Data queues
CRE_DTQ
psnd_dtq / ipsnd_dtq
fsnd_dtq / ifsnd_dtq
rcv_dtq
prcv_dtq

create data queue (static API)send to data queue (polling)
forced send to data queue
receive from data queue
receive from data queue (polling)(7) Time management functions
System time management
isig_tim

supply time tick* If the kernel has a mechanism of updating the system time, isig_tim neednot be supported.
Cyclic handlers
CRE_CYC
sta_cyc
stp_cyccreate cyclic handler (static API)
start cyclic handler operation
stop cyclic handler operation(8) System state management functions
get_tid / iget_tid
reference task ID in the RUNNING state
loc_cpu / iloc_cpu
lock the CPU
unl_cpu / iunl_cpu
unlock the CPU
dis_dspdisable dispatchingena_dspenable dispatching
sns_ctxreference contexts
sns_loc
reference CPU state
sns_dspreference dispatching state
sns_dpnreference dispatch pending state(9) Interrupt management functions
DEF_INH
define interrupt handler (static API)* If ATT_ISR is supported, DEF_INH need not be supported.
(11) System configuration management functions
DEF_EXC
define CPU exception handler (static API)
ATT_INI
attach initialization routine (static API)
Among these static APIs or service calls, the functions that should be supported by the
Automotive Control Profile but are restricted or extended compared to the Standard
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Profile are as follows.
• CRE_TSK
TA_RSTR (= 0x04) can be specified in the task attribute. When TA_RSTR is specified, a restricted task is created.
• CRE_SEM, CRE_FLG, CRE_DTQ
The Automotive Control Profile does not require support for when TA_TPRI is
specified in each object attribute.
• ext_tsk
The behavior when invoked from restricted tasks is undefined. When an error
should be reported, an E_NOSPT error is returned.
• ter_tsk, chg_pri
The behavior when invoked with a restricted task is undefined. When an error
should be reported, an E_NOSPT error is returned.
• slp_tsk, wai_sem, wai_flg, rcv_dtq
The behavior when invoked from a restricted task is undefined. When an error
should be reported, an E_NOSPT error is returned.
[Supplemental Information]
Within the Automotive Control Profile, the behavior when TA_TFIFO is specified as
the eventflag attribute is the same as when TA_TPRI is specified. In addition, since thetask cannot enter the sending waiting state for a data queue, specifying TA_TFIFO or
TA_TPRI for the data queue attribute is meaningless. Therefore, the restriction that
TA_TPRI cannot be specified for the eventflag attribute and the data queues attributepractically means that when TA_TPRI is specified, an error should be returned.

5.3 Version Number of the Specifications
The version number of the ITRON Specifications is in the following form:
Ver. X.YY.ZZ [.WW]
X represents the major version number of the ITRON Specifications. The numbers
below are assigned to the kernel specifications:
1
2
3
4

ITRON1ITRON2 or µITRON (Ver. 2.0)
µITRON3.0µITRON4.0

YY indicates the version number of the updated specification when modifications oradditions are made to its contents. Once the specification is published, YY is updated
to YY = 00, 01, 02, and so on for each version of the specification. For draft specifications or specifications under discussion, on the other hand, one of the letters in YY
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should be ‘A’, ‘B’, or ‘C’.
The X.YY portion in the version number can be referenced through the kernel configuration macro TKERNEL_SPVER and through the return parameter spver of ref_ver
service call. If YY contains ‘A’, ‘B’, or ‘C’, the hexadecimal representation of ‘A’, ‘B’,or ‘C’ is used, respectively.
ZZ is a number identifying the version relating to the specification notation. When
structural changes are made to the specification document or chapters, or when typographical errors are corrected, ZZ is updated to ZZ = 00, 01, 02, and so on.
WW may be used for minor classifications on notations in the specification document.
If WW is omitted, WW is regarded as 00.

5.4 Maker Codes
The TRON Association assigns the maker codes referenced through the kernel configuration macro TKERNEL_MAKER and through the return parameter maker of
ref_ver service call.
At the time of the publication of this specification document, the following makercodes are assigned:
0x00000x00010x00080x00090x000a0x000b0x000c0x000d0x000e0x000f0x00100x00110x00120x00130x00140x00150x01010x01020x01030x01040x01050x0106

No maker code (such as experimental systems)
University of Tokyo
Individuals (or personal businesses)
FUJITSU LIMITED
Hitachi, Ltd.
Matsushita Electric Industrial Co., Ltd.
Mitsubishi Electric Corporation
NEC Corporation
Oki Electric Industry Company, Limited
Toshiba Corporation
ALPS ELECTRIC Co., Ltd.
WACOM Co., Ltd.
Personal Media Corporation
Sony Corporation
Motorola, Inc.
National Semiconductor Corporation
OMRON Corporation
Seiko Precision Inc.
System Algo Co., Ltd.
TOKYO COMPUTER SERVICE Co., Ltd.
Yamaha Corporation
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0x01070x01080x01090x010a0x010b
0x010c0x010d
0x010e0x010f0x01100x01110x0112

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Toshiba Information Systems (JAPAN) Corporation
MiSPO Co., Ltd.
Three Ace Computer Corporation
FIRMWARE SYSTEMS Inc.
eSOL Co., Ltd.
U S Software Corporation
ACCESS CO., LTD.
FUJITSU DEVICES INC.
Accelerated Technology Incorporated
ELMIC SYSTEMS, INC.
FJB Web Technology Ltd.
A. I. Corporation

For the kernels implemented by individuals (or personal businesses), 0x0008 is used as
the maker code. For further identification of the kernel implementor, unique values are
assigned to each individual in the upper 8 bits of the identification number of the kern e l , w h i c h c a n b e r e f e r e n c e d t h r o u g h t h e ke r n e l c o n fi g u r a t i o n m a c r o
TKERNEL_PRID and through the return parameter prid of ref_ver service call.

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Chapter 6 Appendix
6.1 Conditions for Using the Specification and theSpecification Document
The conditions for using the µITRON4.0 Specification and its specification document
are as follows:
Conditions for Using the Specification
The µITRON4.0 Specification is an open specification. Anyone may freely develop,
use, distribute, and sell software that conforms to the µITRON4.0 Specification. Thereis no need to pay a license fee or register to the ITRON Committee of the TRON Association.
However, the ITRON Committee of the TRON Association strongly recommends thatthe following statements (or statements with the same meaning) be included in the documentation of the software, such as the product manuals, conforming to theµITRON4.0 Specification:• TRON is the abbreviation of “The Real-time Operating system Nucleus.”• ITRON is the abbreviation of “Industrial TRON.”• µITRON is the abbreviation of “Micro Industrial TRON.”• TRON, ITRON, and µITRON do not refer to any specific product or products.
The ITRON Committee of the TRON Association also recommends that the following
statements (or statements with the same meaning) be included in the documentation of
the software, such as the product manuals, conforming to the µITRON4.0 Specification:
The µITRON4.0 Specifications is an open real-time kernel specification developed by the ITRON Committee of the TRON Association. The µITRON4.0
Specification document can be obtained from the ITRON Project web site(http://www.itron.gr.jp/).
If you receive permission to modify the specification document to create product manuals (described later), or if you register products to the ITRON-Specification ProductRegistration System (see Section 6.2), you are obliged to include the statements
described above.
Conditions for Using the Specification Document
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mittee of the TRON Association.
The ITRON Committee of the TRON Association grants the permission to copy thewhole or a part of the µITRON4.0 Specification document and to redistribute it intact
without charge or with a distribution fee. However, when a part of the µITRON4.0
Specification document is redistributed, it must clearly state (1) that it is a part of theµITRON4.0 Specification document, (2) which part it was taken, and (3) the method to
obtain the whole µITRON4.0 Specification document.
Modification of the µITRON4.0 Specification document without prior written permission from the ITRON Committee of the TRON Association is strongly prohibited.
The ITRON Committee of the TRON Association permits the members of the TRON
Association to modify the µITRON4.0 Specification document to create, distribute,and sell product manuals. Contact the ITRON Committee for the conditions and theprocedure to get the permission.
Disclaimer
The ITRON Committee of the TRON Association disclaims all warranties with regard
to the µITRON4.0 Specification and its document including all implied warranties.
The ITRON Committee of the TRON Association is not liable for any direct or indirect
damages caused by using the µITRON4.0 Specification or its document.
The ITRON Committee of the TRON Association may revise the µITRON4.0 Specification documentation without notice.

6.2 Maintenance of the Specification and RelatedInformation
Maintenance of the ITRON Specifications and Contact Information
The ITRON Specifications and their documents are developed and maintained by the
ITRON Committee of the TRON Association. Any questions regarding the specifications and their documents should be directed to the following:
ITRON Committee, TRON Association
Katsuta Building 5F
3-39, Mita 1-chome, Minato-ku,
Tokyo 108-0073, JAPANTEL: +81-3-3454-3191
FAX: +81-3-3454-3224
ITRON Project Web Site
The ITRON Committee of the TRON Association maintains the ITRON Project web

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site for distributing information regarding the ITRON Project and Specifications. Various ITRON Specifications and other documents are available at the web site, such as:
introduction to the ITRON Project, the ITRON Newsletter, status of standardization
activities, results of the survey on RTOS uses, list of products registered to the
ITRON-Supplications Product Registration System, information on seminars and trade
show participation, presentation materials used in lectures, and the list of the ITRON
Committee members.
The URL of the ITRON Project Web Site is:
http://www.itron.gr.jp/
The ITRON Newsletter
The ITRON Committee of the TRON Association publishes the ITRON Newsletterbimonthly to widely distribute the latest information regarding the ITRON Project andthe activities of the ITRON Committee. The ITRON Newsletter has both Japanese andEnglish versions. Information regarding additions or corrections to the ITRON Specifications, and information regarding corrections to the books published by the ITRON
Committee are notified with the ITRON Newsletter. The ITRON Newsletter is also
used to introduce products, books, and documents related to the ITRON Specifications,and to notify the events such as seminars and trade shows.
The ITRON Newsletter is included in the TRONWARE magazine (only in Japanese)and the periodicals by the TRON Association. The ITRON Newsletter is also available
at the ITRON Project web site.
ITRON-Specification Product Registration System
In order to promote the use and development of the ITRON Specifications, the ITRON
Committee of the TRON Association provides the ITRON-Specification Product Registration System. The purpose of this system is to create and maintain a list of products
developed by companies that conform to the ITRON Specifications and to promote theuse of the ITRON Specifications and the conforming products. This system is different
from the so-called certification system. It is not intended to certify registered products
to be conformant to the ITRON Specifications.
The list of products registered to the system is available at the ITRON Project web site.
Contact the ITRON Committee if you are interested in registering products that conform to the ITRON Specifications.
Reference documents“THE TRON PROJECT” is published by the TRON Association as a reference for theentire TRON Project. This document includes an introduction to the activities of each
TRON basic and application sub-project, the history of the TRON Project, and the listof the reference regarding the TRON Project.
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For the latest information on the TRON Project, refer to “TRONWARE,” a TRON
Project technical information magazine published bimonthly by Personal Media Corporation. For the research results of the TRON Project, refer to the proceedings of theannual TRON Project International Symposium.
The ITRON Committee of the TRON Association publishes the ITRON Specification
Guidebook as a textbook regarding the ITRON Specifications.
“ITRON Specification Guidebook 2,” supervised by Ken Sakamura, PersonalMedia Corporation, 1994 (ISBN4-89362-133-5).
“ITRON Specifications Guidebook 2” is based on the µITRON3.0 Specification anddoes not correspond to the µITRON4.0 Specification. However, the ITRON Committee is planning to publish an edition that corresponds to the µITRON4.0 Specification.

6.3 Background and Development Process of theSpecification
Background and Development Process of the Specification
The ITRON Committee of the TRON Association started the µITRON4.0 Specification
Study Group to develop the next generation µITRON Specification following theresults of the Hard Real-Time Support Study Group (from November 1996 to March
1998) and of the RTOS Automotive Application Technical Committee (from June 1997
to March 1998). The µITRON4.0 Specification Study Group was an open group whereanyone, including non-members of either the ITRON Committee or the TRON Association, was welcome to participate, thus promoting the involvement of active engineersfrom various fields of embedded system development.
The Kernel Specification Working Group established under the µITRON4.0 Specification Study Group developed the µITRON4.0 Specification. The Kernel Specification
Working Group started the development in April 1998. It organized meetings once or
twice a month until June 1999, when the official specification document was published.
Email discussions were also conducted for the development.
The µITRON4.0 Specification also reflects the requirements and ideas derived from thefollowing investigations: the ITRON TCP/IP API Specification by the Embedded TCP/
IP Technical Committee, the JTRON2.0 Specification by Java Technology on
ITRON-Specification OS Technical Committee, and investigations by the Device
Driver Design Guideline Working Group of the µITRON4.0 Specification Study
Group.
Member List of the ITRON Committee of the TRON Association (in alphabeticalorder)
John Cheuck (Metrowerks Co., Ltd.)
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Shouichi Hachiya (Aplix Corporation)
Makoto Hirayama (Hewlett-Packard Japan, Ltd.)
Noboru Hirose (FIRMWARE SYSTEMS Inc.)
Shigeru Honma (Yamaha Corporation)
Katsuhiko Ishida (Hitachi, Ltd.)
Hidehiro Ishii (YDC Corporation)
Norihiko Ito (Nihon Cygnus Solutions)
Tomihisa Kamada (ACCESS Co., Ltd.)
Tatsuya Kamei (Mitsubishi Electric Corporation)
Kenji Kudou (FUJITSU DEVICES Inc.), Vice-Chair
Akira Matsui (Personal Media Corporation)
Hiroshi Monden (NEC Corporation)
Tetsuo Oe (Oki Electric Industry Company, Limited)
Ken Sakamura (University of Tokyo)
Kazuo Sato (Toshiba Information Systems (JAPAN) Corporation)
Tetsu Shibashita (Mentor Graphics Japan Co., Ltd.)
Hiroaki Takada (Toyohashi University of Technology), Secretary
Tetsuo Takagi (DENSO CREATE Inc.)
Tohru Takeuchi (TRON Association), Secretariat
Kiichiro Tamaru (Toshiba Corporation), Chair
Yasutaka Tsunakawa (Sony Corporation)
Yiroyuki Watanabe (Seiko Instruments Inc.)
Member List of the Kernel Specification Working Group of the µITRON4.0
Specification Study Group (in alphabetical order)
Yoshitaka Adachi (Matsushita Electric Industry Co., Ltd.)
Yoshihiko Aoki (Sanyo Engineering & Construction Inc.)
Shigemasa Asai (Aisin Seiki Co., Ltd.)
Akihito Chiba (NIPPON TELECOMMUNICATIONS CONSULTING
Co., Ltd.)
Kazuhiro Ibuka (Motorola Japan Ltd.)
Jun’ichi Iijima, Secretery
Kazutoyo Inamitsu (FUJITSU DEVICES Inc.)
Katsuhiko Ishida (Hitachi, Ltd.)
Masanori Ishikawa (YDC Corporation)
Kazunori Isomoto (Mazda Motor Corporation)
Norihiko Ito (Nihon Cygnus Solutions)Takanao Ito (Fuji Electric Mie Design Co., Ltd.)
Yoshihisa Iwaki (Honda R&D Co., Ltd.)
Shouichi Hachiya (Aplix Corporation )Shin’ichi Hashimoto (ACCESS Co., Ltd.)
319

µITRON4.0 Specification

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Osamu Higashihara (NEC Information Systems, Ltd.)
Hiroki Hihara (NEC Corporation)
Michitaro Horiuchi (ACCESS Co., Ltd. )Hiroshi Kako (DENSO CORPORATION)
Hironori Kaneda (Data Technology Inc.)
Hiroshi Kawaguchi (HANAZUKA ELECTRIC INDUSTRY Co., Ltd.)Tuyoshi Kodama (Alpine Information System Inc.)
Manabu Kobayakawa (Hitachi, Ltd.)
Masakazu Kobayashi (Hitachi ULSI Systems Co., Ltd.)
Yasuhiro Kobayashi (FUJITSU LIMITED)
Takahiro Kudo (Data Technology Inc.)
Kenji Kudou (FUJITSU DEVICES Inc.)
Tadakatsu Masaki (Matsushita Information Systems Research Laboratory Hiroshima Co., Ltd.)
Takayuki Matsunaga (Yazaki Corporation)
Atsushi Miki (Sumitomo Electric Industries, Ltd.)
Tetsuo Miyauchi (NEC Microcomputer Technology, Ltd.)
Hisaya Miyamoto (Toshiba Corporation)
Hisanori Miyazaki (MiSPO Co., Ltd.)
Kohei Mugitani (Sharp Corporation )Hiroyuki Muraki (Mitsubishi Electric Semiconductor Systems Corporation)
Hiroyuki Nagasaku (CRESCO Ltd.)
Ryuichi Naito (Nippon Business Solution)
Yuiku Nakai (DENSAN Co., Ltd.)
Ken’ichi Nakamura (Nihon Cygnus Solutions)Shigeki Nankaku (Mitsubishi Electric Corporation)
Tomo Onozawa (Aishin Seiki Co., Ltd.)
Masayuki Osajima (ACCESS Co., Ltd.)
Hideto Sakamoto (EST K.K.)
Koji Sato (Toyota Motor Corporation)
Shuji Sato (Toshiba Engineering Corporation)
Tsutomu Sawada (Erg Co., Ltd.), Secretary
Masanobu Shigeta (Fuji Denki Co., Ltd.)
Kazu Shimazaki (SENNET, Inc.)
Masahiro Shukuguchi (Mitsubishi Electric Micro-Computer Application
Software Co., Ltd.)
Hideaki Suganuma (Toyota Motor Corporation)
Kenji Suganuma (DENSO CORPORATION)
Akihiko Sugimoto (Data Technology Inc.)
Hiroaki Takada (Toyohashi University of Technology), Secretary320

µITRON4.0 Specification

Ver. 4.00.00

Shuji Takanashi (Toshiba Corporation)
Yosuke Takano (NEC Corporation)
Tohru Takeuchi (TRON Association), Secretariat
Noriaki Tanaka (DENSO CREATE Inc.)
Kazuhiko Taoka (MiSPO Co., Ltd. )Kazuhiro Terauchi (Toshiba Information Systems (JAPAN) Corporation)
Shin’ichi Tsunashima (ACCESS Co., Ltd.)
Naotaka Uehara (Casio)
Masakazu Uemura (Fuji Electric Mie Design)
Shinjiro Yamada (Hitachi, Ltd.)
Tatsuo Yamada (Motorola Japan Ltd.)
Masaru Yamanaka (Nihon Cygnus Solutions)
Akira Yokozawa (Toshiba Corporation)
Tomoaki Yoshida (Toshiba Corporation)
Miyoko Yoshimura (ERG. Co., Ltd)
Yukio Yoshino (Communication And Technology Systems, Inc.)
Masahiko Watanabe (Communication And Technology Systems, Inc.)
Contributors to the English Translation of the µITRON4.0 Specification
Eva Austria Barcelon (Toyohashi University of Technology)
Christopher G. Brown (U S Software)
Donald Dunstan (U S Software)
Tadahiro Fukaya (FIRMWARE SYSTEMS Inc.)
Shin’ichi Hashimoto (ACCESS Co., Ltd.)
Kazutoyo Inamitsu (FUJITSU DEVICES Inc.)
Kazuhiro Inaoka (Mitsubishi Electric Semiconductor Systems Corporation)
Takeshi Kaneko (A.I.Corporation)
Hiroyuki Kato (A.I.Corporation)
Tsutomu Kindaichi (ELMIC SYSTEMS, INC)
Isao Kubota (ERG Co., Ltd.)
Akira Matsui (Personal Media Corporation)
Koji Mugita (GRAPE SYSTEMS INC.)
Hiroyuki Muraki (Mitsubishi Electric Semiconductor Systems Corporation)
Kohichi Nakamoto (NEC Corporation)
Nicholas James Withcy (U S Software)
Takuya Nomura (Matsushita Electric Industrial Co., Ltd.)
Tatsuo Obata (A.I.Corporation)
Tsutomu Sawada (ERG Co., Ltd.)
Hiroaki Takada (Toyohashi University of Technology)
321

µITRON4.0 Specification

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Tetsuo Takagi (DENSO CREATE Inc.)
Tohru Takeuchi (TRON Association)
Shinjiro Yamada (Hitachi, Ltd.)
Koichi Yasutake (Matsushita Electric Industrial Co., Ltd.)
Akira Yokozawa (Toshiba Corporation)

6.4 Version History
May 10, 1999

Ver. 4.A0.00

May 17, 1999
June 1, 1999
June 10, 1999
June 30, 1999

Ver. 4.A1.00
Ver. 4.B0.00
Ver. 4.B1.00
Ver. 4.00.00

A draft version released for public comments
Unfinished portion completed(Working Group internal version)(Working Group internal version)
Official release published322

µITRON4.0 Specification

Ver. 4.00.00

Chapter 7 References
7.1 Service Call List
(1) Task management functions
ER ercd = cre_tsk ( ID tskid, T_CTSK *pk_ctsk ) ;ER_ID tskid = acre_tsk ( T_CTSK *pk_ctsk ) ;ER ercd = del_tsk ( ID tskid ) ;ER ercd = act_tsk ( ID tskid ) ;ER ercd = iact_tsk ( ID tskid ) ;ER_UINT actcnt = can_act ( ID tskid ) ;ER ercd = sta_tsk ( ID tskid, VP_INT stacd ) ;void ext_tsk ( ) ;void exd_tsk ( ) ;ER ercd = ter_tsk ( ID tskid ) ;ER ercd = chg_pri ( ID tskid, PRI tskpri ) ;ER ercd = get_pri ( ID tskid, PRI *p_tskpri ) ;ER ercd = ref_tsk ( ID tskid, T_RTSK *pk_rtsk ) ;ER ercd = ref_tst ( ID tskid, T_RTST *pk_rtst ) ;(2) Task dependent synchronization functions
ER ercd = slp_tsk ( ) ;ER ercd = tslp_tsk ( TMO tmout ) ;ER ercd = wup_tsk ( ID tskid ) ;ER ercd = iwup_tsk ( ID tskid ) ;ER_UINT wupcnt = can_wup ( ID tskid ) ;ER ercd = rel_wai ( ID tskid ) ;ER ercd = irel_wai ( ID tskid ) ;ER ercd = sus_tsk ( ID tskid ) ;ER ercd = rsm_tsk ( ID tskid ) ;ER ercd = frsm_tsk ( ID tskid ) ;ER ercd = dly_tsk ( RELTIM dlytim ) ;(3) Task exception handling functions
ER ercd = def_tex ( ID tskid, T_DTEX *pk_dtex ) ;ER ercd = ras_tex ( ID tskid, TEXPTN rasptn ) ;ER ercd = iras_tex ( ID tskid, TEXPTN rasptn ) ;ER ercd = dis_tex ( ) ;ER ercd = ena_tex ( ) ;BOOL state = sns_tex ( ) ;ER ercd = ref_tex ( ID tskid, T_RTEX *pk_rtex ) ;323

µITRON4.0 Specification

Ver. 4.00.00(4) Synchronization and communication functions
Semaphores
ER ercd = cre_sem ( ID semid, T_CSEM *pk_csem ) ;ER_ID semid = acre_sem ( T_CSEM *pk_csem ) ;ER ercd = del_sem ( ID semid ) ;ER ercd = sig_sem ( ID semid ) ;ER ercd = isig_sem ( ID semid ) ;ER ercd = wai_sem ( ID semid ) ;ER ercd = pol_sem ( ID semid ) ;ER ercd = twai_sem ( ID semid, TMO tmout ) ;ER ercd = ref_sem ( ID semid, T_RSEM *pk_rsem ) ;Eventflags
ER ercd = cre_flg ( ID flgid, T_CFLG *pk_cflg ) ;ER_ID flgid = acre_flg ( T_CFLG *pk_cflg ) ;ER ercd = del_flg ( ID flgid ) ;ER ercd = set_flg ( ID flgid, FLGPTN setptn ) ;ER ercd = iset_flg ( ID flgid, FLGPTN setptn ) ;ER ercd = clr_flg ( ID flgid, FLGPTN clrptn ) ;ER ercd = wai_flg ( ID flgid, FLGPTN waiptn, MODE wfmode,
FLGPTN *p_flgptn ) ;ER ercd = pol_flg ( ID flgid, FLGPTN waiptn, MODE wfmode,
FLGPTN *p_flgptn ) ;ER ercd = twai_flg ( ID flgid, FLGPTN waiptn, MODE wfmode,
FLGPTN *p_flgptn, TMO tmout ) ;ER ercd = ref_flg ( ID flgid, T_RFLG *pk_rflg ) ;Data queues
ER ercd = cre_dtq ( ID dtqid, T_CDTQ *pk_cdtq ) ;ER_ID dtqid = acre_dtq ( T_CDTQ *pk_cdtq ) ;ER ercd = del_dtq ( ID dtqid ) ;ER ercd = snd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = psnd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = ipsnd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = tsnd_dtq ( ID dtqid, VP_INT data, TMO tmout ) ;ER ercd = fsnd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = ifsnd_dtq ( ID dtqid, VP_INT data ) ;ER ercd = rcv_dtq ( ID dtqid, VP_INT *p_data ) ;ER ercd = prcv_dtq ( ID dtqid, VP_INT *p_data ) ;ER ercd = trcv_dtq ( ID dtqid, VP_INT *p_data, TMO tmout ) ;ER ercd = ref_dtq ( ID dtqid, T_RDTQ *pk_rdtq ) ;Mailboxes
ER ercd = cre_mbx ( ID mbxid, T_CMBX *pk_cmbx ) ;324

µITRON4.0 Specification

Ver. 4.00.00

ER_ID mbxid = acre_mbx ( T_CMBX *pk_cmbx ) ;ER ercd = del_mbx ( ID mbxid ) ;ER ercd = snd_mbx ( ID mbxid, T_MSG *pk_msg ) ;ER ercd = rcv_mbx ( ID mbxid, T_MSG **ppk_msg ) ;ER ercd = prcv_mbx ( ID mbxid, T_MSG **ppk_msg ) ;ER ercd = trcv_mbx ( ID mbxid, T_MSG **ppk_msg,
TMO tmout ) ;ER ercd = ref_mbx ( ID mbxid, T_RMBX *pk_rmbx ) ;(5) Extended synchronization and communication functions
MutexesER ercd = cre_mtx ( ID mtxid, T_CMTX *pk_cmtx ) ;ER_ID mtxid = acre_mtx ( T_CMTX *pk_cmtx ) ;ER ercd = del_mtx ( ID mtxid ) ;ER ercd = loc_mtx ( ID mtxid ) ;ER ercd = ploc_mtx ( ID mtxid ) ;ER ercd = tloc_mtx ( ID mtxid, TMO tmout ) ;ER ercd = unl_mtx ( ID mtxid ) ;ER ercd = ref_mtx ( ID mtxid, T_RMTX *pk_rmtx ) ;Message buffers
ER ercd = cre_mbf ( ID mbfid, T_CMBF *pk_cmbf ) ;ER_ID mbfid = acre_mbf ( T_CMBF *pk_cmbf ) ;ER ercd = del_mbf ( ID mbfid ) ;ER ercd = snd_mbf ( ID mbfid, VP msg, UINT msgsz ) ;ER ercd = psnd_mbf ( ID mbfid, VP msg, UINT msgsz ) ;ER ercd = tsnd_mbf ( ID mbfid, VP msg, UINT msgsz,
TMO tmout ) ;ER_UINT msgsz = rcv_mbf ( ID mbfid, VP msg ) ;ER_UINT msgsz = prcv_mbf ( ID mbfid, VP msg ) ;ER_UINT msgsz = trcv_mbf ( ID mbfid, VP msg, TMO tmout ) ;ER ercd = ref_mbf ( ID mbfid, T_RMBF *pk_rmbf ) ;Rendezvous
ER ercd = cre_por ( ID porid, T_CPOR *pk_cpor ) ;ER_ID porid = acre_por ( T_CPOR *pk_cpor ) ;ER ercd = del_por ( ID porid ) ;ER_UINT rmsgsz = cal_por ( ID porid, RDVPTN calptn, VP msg,
UINT cmsgsz ) ;ER_UINT rmsgsz = tcal_por ( ID porid, RDVPTN calptn, VP msg,
UINT cmsgsz, TMO tmout ) ;ER_UINT cmsgsz = acp_por ( ID porid, RDVPTN acpptn,
RDVNO *p_rdvno, VP msg ) ;325

µITRON4.0 Specification

Ver. 4.00.00

ER_UINT cmsgsz = pacp_por ( ID porid, RDVPTN acpptn,
RDVNO *p_rdvno, VP msg ) ;ER_UINT cmsgsz = tacp_por ( ID porid, RDVPTN acpptn,
RDVNO *p_rdvno, VP msg, TMO tmout ) ;ER ercd = fwd_por ( ID porid, RDVPTN calptn, RDVNO rdvno,
VP msg, UINT cmsgsz ) ;ER ercd = rpl_rdv ( RDVNO rdvno, VP msg, UINT rmsgsz ) ;ER ercd = ref_por ( ID porid, T_RPOR *pk_rpor ) ;ER ercd = ref_rdv ( RDVNO rdvno, T_RRDV *pk_rrdv ) ;(6) Memory pool management functions
Fixed-sized memory pools
ER ercd = cre_mpf ( ID mpfid, T_CMPF *pk_cmpf ) ;ER_ID mpfid = acre_mpf ( T_CMPF *pk_cmpf ) ;ER ercd = del_mpf ( ID mpfid ) ;ER ercd = get_mpf ( ID mpfid, VP *p_blk ) ;ER ercd = pget_mpf ( ID mpfid, VP *p_blk ) ;ER ercd = tget_mpf ( ID mpfid, VP *p_blk, TMO tmout ) ;ER ercd = rel_mpf ( ID mpfid, VP blk ) ;ER ercd = ref_mpf ( ID mpfid, T_RMPF *pk_rmpf ) ;Variable-sized memory pools
ER ercd = cre_mpl ( ID mplid, T_CMPL *pk_cmpl ) ;ER_ID mplid = acre_mpl ( T_CMPL *pk_cmpl ) ;ER ercd = del_mpl ( ID mplid ) ;ER ercd = get_mpl ( ID mplid, UINT blksz, VP *p_blk ) ;ER ercd = pget_mpl ( ID mplid, UINT blksz, VP *p_blk ) ;ER ercd = tget_mpl ( ID mplid, UINT blksz, VP *p_blk,
TMO tmout ) ;ER ercd = rel_mpl ( ID mplid, VP blk ) ;ER ercd = ref_mpl ( ID mplid, T_RMPL *pk_rmpl ) ;(7) Time management functions
System time management
ER ercd = set_tim ( SYSTIM *p_systim ) ;ER ercd = get_tim ( SYSTIM *p_systim ) ;ER ercd = isig_tim ( ) ;Cyclic handlers
ER ercd = cre_cyc ( ID cycid, T_CCYC *pk_ccyc ) ;ER_ID cycid = acre_cyc ( T_CCYC *pk_ccyc ) ;ER ercd = del_cyc ( ID cycid ) ;ER ercd = sta_cyc ( ID cycid ) ;ER ercd = stp_cyc ( ID cycid ) ;326

µITRON4.0 Specification

Ver. 4.00.00

ER ercd = ref_cyc ( ID cycid, T_RCYC *pk_rcyc ) ;Alarm handlers
ER ercd = cre_alm ( ID almid, T_CALM *pk_calm ) ;ER_ID almid = acre_alm ( T_CALM *pk_calm ) ;ER ercd = del_alm ( ID almid ) ;ER ercd = sta_alm ( ID almid, RELTIM almtim ) ;ER ercd = stp_alm ( ID almid ) ;ER ercd = ref_alm ( ID almid, T_RALM *pk_ralm ) ;Overrun handler
ER ercd = def_ovr ( T_DOVR *pk_dovr ) ;ER ercd = sta_ovr ( ID tskid, OVRTIM ovrtim ) ;ER ercd = stp_ovr ( ID tskid ) ;ER ercd = ref_ovr ( ID tskid, T_ROVR *pk_rovr ) ;(8) System state management functions
ER ercd = rot_rdq ( PRI tskpri ) ;ER ercd = irot_rdq ( PRI tskpri ) ;ER ercd = get_tid ( ID *p_tskid ) ;ER ercd = iget_tid ( ID *p_tskid ) ;ER ercd = loc_cpu ( ) ;ER ercd = iloc_cpu ( ) ;ER ercd = unl_cpu ( ) ;ER ercd = iunl_cpu ( ) ;ER ercd = dis_dsp ( ) ;ER ercd = ena_dsp ( ) ;BOOL state = sns_ctx ( ) ;BOOL state = sns_loc ( ) ;BOOL state = sns_dsp ( ) ;BOOL state = sns_dpn ( ) ;ER ercd = ref_sys ( T_RSYS *pk_rsys ) ;(9) Interrupt management functions
ER ercd = def_inh ( INHNO inhno, T_DINH *pk_dinh ) ;ER ercd = cre_isr ( ID isrid, T_CISR *pk_cisr ) ;ER_ID isrid = acre_isr ( T_CISR *pk_cisr ) ;ER ercd = del_isr ( ID isrid ) ;ER ercd = ref_isr ( ID isrid, T_RISR *pk_risr ) ;ER ercd = dis_int ( INTNO intno ) ;ER ercd = ena_int ( INTNO intno ) ;ER ercd = chg_ixx ( IXXXX ixxxx ) ;ER ercd = get_ixx ( IXXXX *p_ixxxx ) ;327

µITRON4.0 Specification

Ver. 4.00.00(10) Service call management functions
ER ercd = def_svc ( FN fncd, T_DSVC *pk_dsvc ) ;ER_UINT ercd = cal_svc ( FN fncd, VP_INT par1, VP_INT par2,...) ;(11) System configuration management functions
ER ercd = def_exc ( EXCNO excno, T_DEXC *pk_dexc ) ;ER ercd = ref_cfg ( T_RCFG *pk_rcfg ) ;ER ercd = ref_ver ( T_RVER *pk_rver ) ;7.2 Static API List
(1) Task management functions
CRE_TSK ( ID tskid, { ATR tskatr, VP_INT exinf, FP task,
PRI itskpri, SIZE stksz, VP stk } ) ;(3) Task exception handling functions
DEF_TEX ( ID tskid, { ATR texatr, FP texrtn } ) ;(4) Synchronization and communication functions
CRE_SEM ( ID semid, { ATR sematr, UINT isemcnt,
UINT maxsem } ) ;CRE_FLG ( ID flgid, { ATR flgatr, FLGPTN iflgptn } ) ;CRE_DTQ ( ID dtqid, { ATR dtqatr, UINT dtqcnt, VP dtq } ) ;CRE_MBX ( ID mbxid, { ATR mbxatr, PRI maxmpri,
VP mprihd } ) ;(5) Extended synchronization and communication functions
CRE_MTX ( ID mtxid, { ATR mtxatr, PRI ceilpri } ) ;CRE_MBF ( ID mbfid, { ATR mbfatr, UINT maxmsz, SIZE mbfsz,
VP mbf } ) ;CRE_POR ( ID porid, { ATR poratr, UINT maxcmsz,
UINT maxrmsz } ) ;(6) Memory pool management functions
CRE_MPF ( ID mpfid, { ATR mpfatr, UINT blkcnt, UINT blksz,
VP mpf } ) ;CRE_MPL ( ID mplid, { ATR mplatr, SIZE mplsz, VP mpl } ) ;(7) Time management functions
CRE_CYC ( ID cycid, { ATR cycatr, VP_INT exinf, FP cychdr,
RELTIM cyctim, RELTIM cycphs } ) ;CRE_ALM ( ID almid, { ATR almatr, VP_INT exinf, FP almhdr } ) ;DEF_OVR ( { ATR ovratr, FP ovrhdr } ) ;328

µITRON4.0 Specification

Ver. 4.00.00(9) Interrupt management functions
DEF_INH ( INHNO inhno, { ATR inhatr, FP inthdr } ) ;ATT_ISR ( { ATR isratr, VP_INT exinf, INTNO intno, FP isr } ) ;(10) Service call management functions
DEF_SVC ( FN fncd, { ATR svcatr, FP svcrtn } ) ;(11) System configuration management functions
DEF_EXC ( EXCNO excno, { ATR excatr, FP exchdr } ) ;ATT_INI ( { ATR iniatr, VP_INT exinf, FP inirtn } ) ;7.3 Static APIs and Service Calls in the Standard
Profile(1) Task management functions
CRE_TSK
act_tsk / iact_tsk
can_act
ext_tsk
ter_tsk
chg_priget_priCreate Task (Static API)
Activate Task
Cancel Task Activation Requests
Terminate Invoking Task
Terminate Task
Change Task Priority
Reference Task Priority(2) Task dependent synchronization functions
slp_tskPut Task to Sleep
tslp_tsk
Put Task to Sleep (with Timeout)
wup_tsk / iwup_tsk
Wakeup Task
can_wup
Cancel Task Wakeup Requests
rel_wai / irel_wai
Release Task from Waiting
sus_tsk
Suspend Task
rsm_tsk
Resume Suspended Task
frsm_tsk
Forcibly Resume Suspended Task
dly_tsk
Delay Task
(3) Task exception handling functions
DEF_TEXDefine Task Exception Handling Routine (StaticAPI)
ras_tex / iras_tex
Raise Task Exception Handling
dis_tex
Disable Task Exceptions
ena_tex
Enable Task Exceptions
sns_tex
Reference Task Exception Handling State

329

µITRON4.0 Specification

Ver. 4.00.00(4) Reference Task Exception Handling State
Semaphores
CRE_SEM
sig_sem / isig_sem
wai_sem
pol_sem
twai_sem

Create Semaphore (Static API)
Release Semaphore Resource
Acquire Semaphore Resource
Acquire Semaphore Resource (Polling)
Acquire Semaphore Resource (with Timeout)

Eventflags
CRE_FLG
set_flg / iset_flg
clr_flg
wai_flg
pol_flg
twai_flg

Create Eventflag (Static API)Set Eventflag
Clear Eventflag
Wait for Eventflag
Wait for Eventflag (Polling)
Wait for Eventflag (with Timeout)

Data queues
CRE_DTQ
snd_dtq
psnd_dtq / ipsnd_dtq
tsnd_dtq
fsnd_dtq / ifsnd_dtq
rcv_dtq
prcv_dtq
trcv_dtq

Create Data Queue (Static API)
Send to Data Queue
Send to Data Queue (Polling)
Send to Data Queue (with Timeout)
Forced Send to Data Queue
Receive from Data Queue
Receive from Data Queue (Polling)
Receive from Data Queue (with Timeout)

Mailboxes
CRE_MBX
snd_mbx
rcv_mbx
prcv_mbx
trcv_mbx

Create Mailbox (Static API)
Send to Mailbox
Receive from Mailbox
Receive from Mailbox (Polling)
Receive from Mailbox (with Timeout)(6) Memory pool management functions
Fixed-sized memory pools
CRE_MPF
get_mpf
pget_mpf
tget_mpf
rel_mpf

Create Fixed-Sized Memory Pool (Static API)
Acquire Fixed-Sized Memory Block
Acquire Fixed-Sized Memory Block (Polling)
Acquire Fixed-Sized Memory Block (with Timeout)
Release Fixed-Sized Memory Block(7) Time management functions
System time management
set_timSet System Time330

µITRON4.0 Specification
get_timisig_tim

Ver. 4.00.00
Reference System Time
Supply Time Tick

* If the kernel has a mechanism of updating the system time, isig_tim neednot be supported.
Cyclic handlers
CRE_CYC
sta_cyc
stp_cycCreate Cyclic Handler (Static API)
Start Cyclic Handler Operation
Stop Cyclic Handler Operation(8) System state management functions
rot_rdq / irot_rdq
Rotate Task Precedence
get_tid / iget_tid
Reference Task ID in the RUNNING State
loc_cpu / iloc_cpu
Lock the CPU
unl_cpu / iunl_cpu
Unlock the CPU
dis_dsp
Disable Dispatchingena_dsp
Enable Dispatching
sns_ctx
Reference Contexts
sns_loc
Reference CPU State
sns_dsp
Reference Dispatching State
sns_dpn
Reference Dispatch Pending State(9) Interrupt management functions
DEF_INH
Define Interrupt Handler (Static API)* If ATT_ISR is supported, DEF_INH need not be supported.
(11) System configuration management functions
DEF_EXC
Define CPU Exception Handler (Static API)
ATT_INI
Attach Initialization Routine (Static API)

7.4 Data Types
The data types, except those for packets, defined in the µITRON4.0 Specification are as
follows:
B
H
W
D

Signed 8-bit integer
Signed 16-bit integer
Signed 32-bit integer
Signed 64-bit integer

UB
UH
UW
UD

Unsigned 8-bit integer
Unsigned 16-bit integer
Unsigned 32-bit integer
Unsigned 64-bit integer

331

µITRON4.0 Specification

Ver. 4.00.00

VB
VH
VW
VD

8-bit value with unknown data type16-bit value with unknown data type32-bit value with unknown data type64-bit value with unknown data type

VP
FP

Pointer to an unknown data type
Processing unit start address (pointer to a function)

INT
UINT

Signed integer for the processor
Unsigned integer for the processor

BOOL

Boolean value (TRUE or FALSE)

FN
ER
ID
ATR
STAT
MODE
PRI
SIZE

Function code (signed integer)
Error code (signed integer)
Object ID number (signed integer)
Object attribute (unsigned integer)
Object state (unsigned integer)
Service call operational mode (unsigned integer)
Priority (signed integer)
Memory area size (unsigned integer)

TMO

Timeout (signed integer, unit of time is implementation-defined)
Relative time (unsigned integer, unit of time is implementation-defined)
System time (unsigned integer, unit of time is implementation-defined)

RELTIM
SYSTIM
VP_INT

Pointer to an unknown data type, or a signed integer for theprocessor

ER_BOOL
ER_ID

Error code or a boolean value (signed integer)
Error code or an object ID number (signed integers and negative ID numbers cannot be represented)
Error code or an unsigned integer (the number of available
bits for an unsigned integer is one bit shorter than UINT)

ER_UINTTEXPTNFLGPTN
T_MSG
T_MSG_PRIRDVPTNRDVNOOVRTIMBit pattern for the task exception code (unsigned integer)
Bit pattern of the eventflag (unsigned integer)
Message header for a mailbox
Message header with a message priority for a mailbox
Bit pattern of the rendezvous condition (unsigned integer)
Rendezvous number
Processor time (unsigned integer, unit of time is implementation-defined)

332

µITRON4.0 Specification
INHNO
INTNO
IXXXX
EXCNO

Ver. 4.00.00

Interrupt handler number
Interrupt number
Interrupt mask
CPU exception handler number

Among the above data types, the definition of the following data type is standardized:
typedef struct t_msg_pri {T_MSG
msgque ;PRI
msgpri ;} T_MSG_PRI ;/* Message header *//* Message priority */[Standard Profile]
The data types, except those for packets, that must be defined in the Standard Profile,their minimum number of bits, and their unit of time are as follows:B
H
W

Signed 8-bit integer
Signed 16-bit integer
Signed 32-bit integer

UB
UH
UW

Unsigned 8-bit integer
Unsigned 16-bit integer
Unsigned 32-bit integer

VB
VH
VW

8-bit value with unknown data type16-bit value with unknown data type32-bit value with unknown data type

VP
FP

Pointer to an unknown data type
Processing unit start address (pointer to a function)

INT
UINT

Signed integer for the processor (16 or more bits)
Unsigned integer for the processor (16 or more bits)

BOOL

Boolean value (TRUE or FALSE)

FN
ER
ID
ATR
STAT
MODE

Function code (signed integer, 16 or more bits)
Error code (signed integer, 8 or more bits)
Object ID number (signed integer, 16 or more bits)
Object attribute (unsigned integer, 8 or more bits)
Object state (unsigned integer, 16 or more bits)
Service call operational mode (unsigned integer, 8 or morebits)
Priority (signed integer, 16 or more bits)
Memory area size (unsigned integer, equal to the number ofbits in a pointer)

PRI
SIZE
TMO

Timeout (signed integer, 16 or more bits, unit of time is 1
msec)
333

µITRON4.0 Specification
RELTIM
SYSTIM

Ver. 4.00.00

Relative time (unsigned integer, 16 or more bits, unit of timeis 1 msec)
System time (unsigned integer, 16 or more bits, unit of time is1 msec)

VP_INT

Pointer to an unknown data type, or a signed integer for theprocessor

ER_UINT

Error code or an unsigned integer (the number of available
bits for an unsigned integer is one bit shorter than UINT)TEXPTNBit pattern for the task exception code (unsigned integer, 16 ormore bits)
Bit pattern of the eventflag (unsigned integer, 16 or more bits)
Message header for a mailbox
Message header with a message priority for a mailbox
Interrupt handler number (when DEF_INH is supported)
Interrupt number (when ATT_ISR is supported)
CPU exception handler number

FLGPTN
T_MSG
T_MSG_PRI
INHNO
INTNO
EXCNO

7.5 Packet Formats(1) Task management functions
Task creation information packet:
typedef struct t_ctsk {ATRtskatr ;/* Task attribute */VP_INT
exinf ;/* Task extended information */FPtask ;/* Task start address */PRI
itskpri ;/* Task initial priority */SIZEstksz ;/* Task stack size (in bytes) */VP
stk ;/* Base address of task stack space *//* Other implementation specific fields may be added. */} T_CTSK ;Task state packet:
typedef struct t_rtsk {STAT
tskstat ;PRI
tskpri ;PRI
tskbpri ;STAT
tskwait ;ID
wobjid ;
TMO
UINT
UINT
UINT

lefttmo ;actcnt ;wupcnt ;suscnt ;/* Task state *//* Task current priority *//* Task base priority *//* Reason for waiting *//* Object ID number for which the task iswaiting *//* Remaining time until timeout *//* Activation request count *//* Wakeup request count *//* Suspension count */334

µITRON4.0 Specification

Ver. 4.00.00/* Other implementation specific fields may be added. */} T_RTSK ;Task state packet (simplified version):
typedef struct t_rtst {STAT
tskstat ;/* Task state */STAT
tskwait ; /* Reason for waiting *//* Other implementation specific fields may be added. */} T_RTST ;(3) Task exception handling functions
Task exception handling routine definition information packet:
typedef struct t_dtex {ATR
texatr ;/* Task exception handling routine
attribute */FP
texrtn ;/* Task exception handling routine start
address *//* Other implementation specific fields may be added. */} T_DTEX ;Task exception handling state packet:
typedef struct t_rtex {STAT
texstat ;/* Task exception state */TEXPTN
pndptn ; /* Pending exception code *//* Other implementation specific fields may be added. */} T_RTEX ;(4) Synchronization and communication functions
Semaphore creation information packet:
typedef struct t_csem {ATR
sematr ;/* Semaphore attribute */UINT
isemcnt ; /* Initial semaphore resource count */UINTmaxsem ; /* Maximum semaphore resource count *//* Other implementation specific fields may be added. */} T_CSEM ;Semaphore state packet:
typedef struct t_rsem {IDwtskid ;/* ID number of the task at the head of thesemaphore’s wait queue */UINTsemcnt ; /* Current semaphore resource count *//* Other implementation specific fields may be added. */} T_RSEM ;Eventflag creation information packet:
typedef struct t_cflg {ATR
flgatr ;/* Eventflag attribute */FLGPTN
iflgptn ;/* Initial value of the eventflag bit
pattern *//* Other implementation specific fields may be added. */335

µITRON4.0 Specification

Ver. 4.00.00} T_CFLG ;Eventflag state packet:
typedef struct t_rflg {IDwtskid ;/* ID number of the task at the head of theeventflag’s wait queue */FLGPTN
flgptn ;/* Current eventflag bit pattern *//* Other implementation specific fields may be added. */} T_RFLG ;Data queue creation information packet:
typedef struct t_cdtq {ATR
dtqatr ;/* Data queue attribute */UINT
dtqcnt ;/* Capacity of the data queue area (thenumber of data elements) */VP
dtq ;/* Start address of the data queue area *//* Other implementation specific fields may be added. */} T_CDTQ ;Data queue state packet:
typedef struct t_rdtq {IDstskid ;/* ID number of the task at the head of thedata queue’s send-wait queue */IDrtskid ;/* ID number of the task at the head of thedata queue’s receive-wait queue */UINT
sdtqcnt ; /* The number of data elements in the data
queue *//* Other implementation specific fields may be added. */} T_RDTQ ;Mailbox creation information packet:
typedef struct t_cmbx {ATR
mbxatr ;/* Mailbox attribute */PRI
maxmpri ; /* Maximum message priority */VPmprihd ; /* Start address of the area for message
queue headers for each message
priority *//* Other implementation specific fields may be added. */} T_CMBX ;Mailbox state packet:
typedef struct t_rmbx {ID
wtskid ;/* ID number of the task at the head of
mailbox’s wait queue */T_MSG * pk_msg ; /* Start address of the message packet atthe head of the message queue *//* Other implementation specific fields may be added. */} T_RMBX ;336

µITRON4.0 Specification

Ver. 4.00.00(5) Extended synchronization and communication functions
Mutex creation information packet:
typedef struct t_cmtx {ATR
mtxatr ;/* Mutex attribute */PRI
ceilpri ;/* Mutex ceiling priority *//* Other implementation specific fields may be added. */} T_CMTX ;Mutex state packet:
typedef struct t_rmtx {IDhtskid ;/* ID number of the task that locks the
mutex */
ID
wtskid ;/* ID number of the task at the head of the
mutex’s wait queue *//* Other implementation specific fields may be added. */} T_RMTX ;Message buffer creation information packet:
typedef struct t_cmbf {ATR
mbfatr ;/* Message buffer attribute */UINTmaxmsz ; /* Maximum message size (in bytes) */SIZE
mbfsz ;/* Size of message buffer area (in bytes) */VP
mbf ;/* Start sddress of message buffer area *//* Other implementation specific fields may be added. */} T_CMBF ;Message buffer state packet:
typedef struct t_rmbf {IDstskid ;/* ID number of the task at the head of themessage buffer’s send-wait queue */IDrtskid ;/* ID number of the task at the head of themessage buffer’s receive-wait queue */UINTsmsgcnt ; /* The number of messages in the message
buffer */SIZE
fmbfsz ;/* Size of free message buffer area in bytes,
without the minimum control areas *//* Other implementation specific fields may be added. */} T_RMBF ;Rendezvous port creation information packet:
typedef struct t_cpor {ATR
poratr ;/* Rendezvous port attribute */UINTmaxcmsz ; /* Maximum calling message size (inbytes) */UINT
maxrmsz ; /* Maximum return message size (inbytes) *//* Other implementation specific fields may be added. */} T_CPOR ;337

µITRON4.0 Specification

Ver. 4.00.00

Rendezvous port state packet:
typedef struct t_rpor {IDctskid ;/* ID number of the task at the head of therendezvous port’s call-wait queue */IDatskid ;/* ID number of the task at the head of therendezvous port’s accept-wait queue *//* Other implementation specific fields may be added. */} T_RPOR ;Rendezvous state packet:
typedef struct t_rrdv {ID
wtskid ;/* ID number of the task in the termination
waiting state for the rendezvous *//* Other implementation specific fields may be added. */} T_RRDV ;(6) Memory pool management functions
Fixed-sized memory pool creation information packet:
typedef struct t_cmpf {ATR
mpfatr ;/* Fixed-sized memory pool attribute */UINT
blkcnt ;/* Total number of memory blocks */UINTblksz ;/* Memory block size (in bytes) */VP
mpf ;/* Start address of the fixed-sized memory
pool area *//* Other implementation specific fields may be added. */} T_CMPF ;Fixed-sized memory pool state packet:
typedef struct t_rmpf {IDwtskid ;/* ID number of the task at the head of the
fixed-sized memory pool’s wait
queue */
UINT
fblkcnt ;/* Number of free memory blocks in the
fixed-sized memory pool *//* Other implementation specific fields may be added. */} T_RMPF ;Variable-sized memory pool creation information packet:
typedef struct t_cmpl {ATR
mplatr ;/* Variable-sized memory pool attribute */SIZEmplsz ;/* Size of the variable-sized memory poolarea (in bytes) */VP
mpl ;/* Start address of the variable-sized
memory pool area *//* Other implementation specific fields may be added. */} T_CMPL ;Variable-sized memory pool state packet:
typedef struct t_rmpl {338

µITRON4.0 Specification
ID

Ver. 4.00.00
wtskid ;/* ID number of the task at the head of thevariable-sized memory pool’s wait
queue */
SIZE
fmplsz ;/* Total size of free memory blocks in thevariable-sized memory pool (inbytes) */UINT
fblksz ;/* Maximum memory block size available(in bytes) *//* Other implementation specific fields may be added. */} T_RMPL ;(7) Time management functions
Cyclic handler creation information packet:
typedef struct t_ccyc {ATR
cycatr ;/* Cyclic handler attribute */VP_INT
exinf ;/* Cyclic handler extended information */FP
cychdr ;/* Cyclic handler start address */RELTIM
cyctim ;/* Cyclic handler activation cycle */RELTIM
cycphs ;/* Cyclic handler activation phase *//* Other implementation specific fields may be added. */} T_CCYC ;Cyclic handler state packet:
typedef struct t_rcyc {STAT
cycstat ;/* Cyclic handler operational state */RELTIM
lefttim ;/* Time left before the next activation *//* Other implementation specific fields may be added. */} T_RCYC ;Alarm handler creation information packet:
typedef struct t_calm {ATR
almatr ;/* Alarm handler attribute */VP_INT
exinf ;/* Alarm handler extended information */FP
almhdr ; /* Alarm handler start address *//* Other implementation specific fields may be added. */} T_CALM ;Alarm handler state packet:
typedef struct t_ralm {STAT
almstat ; /* Alarm handler operational state */RELTIM
lefttim ;/* Time left before the activation *//* Other implementation specific fields may be added. */} T_RALM ;Overrun handler definition information packet:
typedef struct t_dovr {ATR
ovratr ;/* Overrun handler attribute */FP
ovrhdr ;/* Overrun handler start address *//* Other implementation specific fields may be added. */} T_DOVR ;339

µITRON4.0 Specification

Ver. 4.00.00

Overrun handler state packet:
typedef struct t_rovr {STAT
ovrstat ;/* Overrun handler operational state */OVRTIM leftotm ;/* Remaining processor time *//* Other implementation specific fields may be added. */} T_ROVR ;(8) System state management functions
System state packet:
typedef struct t_rsys {/* Implementation specific fields */} T_RSYS ;(9) Interrupt management functions
Interrupt handler definition information packet:
typedef struct t_dinh {ATR
inhatr ;/* Interrupt handler attribute */FP
inthdr ;/* Interrupt handler start address *//* Other implementation specific fields may be added. */} T_DINH ;Interrupt service routine creation information packet:
typedef struct t_cisr {ATR
isratr ;/* Interrupt service routine attribute */VP_INT
exinf ;/* Interrupt service routine extended
information */INTNO
intno ;/* Interrupt number to which the interrupt
service routine is to be attached */FP
isr ;/* Interrupt service routine start sddress *//* Other implementation specific fields may be added. */} T_CISR ;Interrupt service routine state packet:
typedef struct t_risr {/* Implementaion-specific fields */} T_RISR ;(10) Service call management functions
Extended service call definition information packet:
typedef struct t_dsvc {ATR
svcatr ;/* Extended service call attribute */FP
svcrtn ;/* Extended service call routine start
address *//* Other implementation specific fields may be added. */} T_DSVC ;340

µITRON4.0 Specification

Ver. 4.00.00(11) System configuration management functions
CPU exception handler definition information packet:
typedef struct t_dexc {ATR
excatr ;/* CPU exception handler attribute */FP
exchdr ;/* CPU exception handler start address *//* Other implementation specific fields may be added. */} T_DEXC ;Configuration information packet:
typedef struct t_rcfg {/* Implementation specific fields */} T_RCFG ;Version information packet:
typedef struct t_rver {UHmaker ;UH
prid ;UH
spver ;UHUH

prver ;
prno[4] ;/* Kernel maker’s code *//* Identification number of the kernel *//* Version number of the ITRON
Specification *//* Version number of the kernel *//* Management information of the kernel
product */} T_RVER ;7.6 Constants and Macros(1) Object Attributes
TA_HLNG

0x00

TA_ASM

0x01

TA_TFIFO
TA_TPRI

0x00
0x01

Task wait queue is in FIFO order
Task wait queue is in task priority order

TA_MFIFO
TA_MPRI

0x00
0x02

Message queue is in FIFO orderMessage queue is in message priority order

TA_ACT
TA_RSTR0x02
0x04

Task is activated after the creation
Restricted task

TA_WSGL

0x00

TA_WMUL

0x02

TA_CLR

0x04

Only one task is allowed to be in the waiting state forthe eventflag
Multiple tasks are allowed to be in the waiting state
for the eventflag
Eventflag’s bit pattern is cleared when a task is

Start a processing unit through a high-level language
interface
Start a processing unit through an assembly language
interface341

µITRON4.0 Specification

Ver. 4.00.00
released from the waiting state for that eventflag

TA_INHERITTA_CEILING

0x02
0x03

Mutex uses the priority inheritance protocol
Mutex uses the priority ceiling protocol

TA_STA

0x02

TA_PHS

0x04

Cyclic handler is in an operational state after the creation
Cyclic handler is activated preserving the activation
phase(2) Service Call Operational Mode
TWF_ANDWTWF_ORW

0x00
0x01

AND waiting condition for an eventflag
OR waiting condition for an eventflag

TTS_RUNTTS_RDY
TTS_WAITTS_SUSTTS_WASTTS_DMT

0x01
0x02
0x04
0x08
0x0c
0x10

RUNNING state
READY state
WAITING state
SUSPENDED state
WAITING-SUSPENDED state
DORMANT state

TTW_SLPTTW_DLY
TTW_SEM
TTW_FLG
TTW_SDTQ
TTW_RDTQ
TTW_MBX
TTW_MTX
TTW_SMBF
TTW_RMBF
TTW_CAL
TTW_ACP
TTW_RDVTTW_MPF
TTW_MPL

0x00010x00020x00040x00080x00100x00200x00400x00800x01000x02000x04000x08000x10000x20000x4000

TTEX_ENATTEX_DIS

0x00
0x01

Task exception enabled state
Task exception disabled state

TCYC_STP
TCYC_STA

0x00
0x01

Cyclic handler is in a non-operational state
Cyclic handler is in an operational state

TALM_STP

0x00

Alarm handler is in a non-operational state(3) Object States

Sleeping state
Delayed state
Waiting state for a semaphore resource
Waiting state for an eventflag
Sending waiting state for a data queue
Receiving waiting state for a data queue
Receiving waiting state for a mailbox
Waiting state for a mutex
Sending waiting state for a message buffer
Receiving waiting state for a message buffer
Calling waiting state for a rendezvous
Accepting waiting state for a rendezvous
Terminating waiting state for a rendezvous
Waiting state for a fixed-sized memory block
Waiting state for a variable-sized memory block

342

µITRON4.0 Specification

Ver. 4.00.00

TALM_STA

0x01

Alarm handler is in an operational state

TOVR_STPTOVR_STA

0x00
0x01

Processor time limit is not set
Processor time limit is set

TSK_SELF
TSK_NONE00

Specifying invoking task
No applicable task

TPRI_SELF
TPRI_INI

00

Specifying the base priority of the invoking task
Specifying the initial priority of the task(4) Other constants(5) Macros
ER mercd = MERCD ( ER ercd )This macro retrieves the main error code from an error code.
ER sercd = SERCD ( ER ercd )This macro retrieves the sub error code from an error code.

7.7 Kernel Configuration Constants and Macros(1) Priority Range
TMIN_TPRI
TMAX_TPRI

Minimum task priority (= 1)
Maximum task priority

TMIN_MPRI
TMAX_MPRI

Minimum message priority (= 1)
Maximum message priority(2) Version Information
TKERNEL_MAKER
TKERNEL_PRID
TKERNEL_SPVER
TKERNEL_PRVER

Kernel maker code
Identification number of the kernel
Version number of the ITRON Specification
Version number of the kernel(3) Maximum Nesting/Queueing Count
TMAX_ACTCNTTMAX_WUPCNTTMAX_SUSCNT

Maximum activation request countMaximum wakeup request countMaximum suspension count(4) Number of Bits in Bitpatterns
TBIT_TEXPTN

Number of bits in the task exception code343

µITRON4.0 Specification
TBIT_FLGPTNTBIT_RDVPTN

Ver. 4.00.00
Number of bits in an eventflag
Number of bits in a rendezvous condition(5) Time Tick Period
TIC_NUME
TIC_DENO

Time tick period numerator
Time tick period denominator(6) Required Memory Size
SIZE dtqsz = TSZ_DTQ ( UINT dtqcnt )Total required size of the data queue area in bytes necessary to store dtqcnt
data elements
SIZE mprihdsz = TSZ_MPRIHD ( PRI maxmpri )Total required size in bytes of the area for message queue headers for each message priority, when the maximum message priority is maxmpri
SIZE mbfsz = TSZ_MBF ( UINT msgcnt, UINT msgsz )Approximate required size of the message buffer area in bytes necessary to store
msgcnt messages each consisting of msgsz bytes
SIZE mpfsz = TSZ_MPF ( UINT blkcnt, UINT blksz )Total required size of the fixed-size memory pool area in bytes necessary toallocate blkcnt memory blocks each of size blksz bytes
SIZE mplsz = TSZ_MPL ( UINT blkcnt, UINT blksz )Approximate size in bytes necessary to allocate blkcnt memory blocks each ofsize blksz bytes(7) Others
TMAX_MAXSEM

Maximum value of the maximum definable semaphore
resource count

7.8 Error Code List
E_SYS
E_NOSPT
E_RSFN
E_RSATR
E_PAR
E_ID
E_CTX

–5
–9
–10
–11
–17
–18
–25

System error
Unsupported function
Reserved function code
Reserved attribute
Parameter error
Invalid ID number
Context error

344

µITRON4.0 Specification
E_MACV
E_OACV
E_ILUSE
E_NOMEM
E_NOID
E_OBJ
E_NOEXSE_QOVR
E_RLWAIE_TMOUT
E_DLT
E_CLS
E_WBLK
E_BOVR

–26
–27
–28
–33
–34
–41
–42
–43
–49
–50
–51
–52
–57
–58

Ver. 4.00.00
Memory access violation
Object access violation
Illegal service call use
Insufficient memory
No ID number available
Object state error
Non-existent object
Queue overflow
Forced release from waiting
Polling failure or timeout
Waiting object deleted
Waiting object state changed
Non-blocking call accepted
Buffer overflow

7.9 Function Code List
–0x01
–0x05
–0x09
–0x0d
–0x11
–0x15
–0x19
–0x1d
–0x21
–0x25
–0x29
–0x2d
–0x31
–0x35
–0x39
–0x3d
–0x41
–0x45
–0x49
–0x4d
–0x51

–0
reserved
cre_tsk
sta_tsk
chg_prislp_tsk
rel_wai
dly_tsk
dis_texcre_sem
wai_sem
cre_flg
wai_flg
cre_dtq
snd_dtq
rcv_dtq
cre_mbx
rcv_mbx
cre_mpf
get_mpf
set_timsta_cyc–1
reserved
del_tsk
ext_tsk
get_pritslp_tsk
sus_tsk
reserved
ena_texdel_sem
pol_sem
del_flg
pol_flg
del_dtq
psnd_dtq
prcv_dtq
del_mbx
prcv_mbx
del_mpf
pget_mpf
get_tim
stp_cyc345–2
reserved
act_tsk
exd_tsk
ref_tsk
wup_tsk
rsm_tsk
def_texsns_texsig_sem
twai_sem
set_flg
twai_flg
reserved
tsnd_dtq
trcv_dtq
snd_mbx
trcv_mbx
rel_mpf
tget_mpf
cre_cyc
ref_cyc–3
reserved
can_act
ter_tsk
ref_tstcan_wupfrsm_tsk
ras_tex
ref_texreserved
ref_sem
clr_flg
ref_flg
reserved
fsnd_dtq
ref_dtq
reserved
ref_mbx
reserved
ref_mpf
del_cycreserved

µITRON4.0 Specification
–0x55
–0x59
–0x5d
–0x61
–0x65
–0x69
–0x6d
–0x71
–0x75
–0x79
–0x7d
–0x81
–0x85
–0x89
–0x8d
–0x91
–0x95
–0x99
–0x9d
–0xa1
–0xa5
–0xa9
–0xad
–0xb1
–0xb5
–0xb9
–0xbd
–0xc1
–0xc5
–0xc9
–0xcd
–0xd1
–0xd5
–0xd9
–0xdd
–0xe1
–0xe5
–0xe9
–0xed

Ver. 4.00.00

rot_rdq
get_tidreserved
reserved
loc_cpu
unl_cpu
dis_dspena_dspsns_ctx
sns_loc
sns_dspsns_dpn
ref_sysreserved
reserved
reserved
def_inhcre_isr
del_isr
ref_isr
dis_int
ena_int
chg_ixx
get_ixx
def_svc
def_exc
ref_cfg
ref_veriact_tsk
iwup_tsk
irel_waiiras_tex
isig_sem
iset_flg
ipsnd_dtq ifsnd_dtq
irot_rdq
iget_tid
iloc_cpu
iunl_cpu
isig_tim
reserved
reserved
reserved
cre_mtx
del_mtx
unl_mtx
reserved
loc_mtx
ploc_mtx
tloc_mtx
ref_mtx
cre_mbf
del_mbf
reserved
reserved
snd_mbf
psnd_mbf tsnd_mbf
reserved
rcv_mbf
prcv_mbf
trcv_mbf
ref_mbf
cre_pordel_por
cal_por
tcal_por
acp_por
pacp_portacp_por
fwd_por
rpl_rdv
ref_porref_rdv
reserved
cre_mpldel_mplrel_mplreserved
get_mplpget_mpl
tget_mpl
ref_mplcre_alm
del_alm
sta_alm
stp_alm
ref_alm
reserved
reserved
reserved
def_ovr
sta_ovr
stp_ovr
ref_ovr
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
acre_tsk
acre_sem
acre_flg
acre_dtq
acre_mbx
acre_mtx
acre_mbf
acre_poracre_mpf
acre_mpl
acre_cyc
acre_alm
acre_isr
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
reserved
implementation-specific service calls
implementation-specific service calls
implementation-specific service calls
implementation-specific service calls
346

µITRON4.0 Specification
–0xf1
–0xf5
–0xf9
–0xfd

Ver. 4.00.00
implementation-specific service calls
implementation-specific service calls
implementation-specific service calls
implementation-specific service calls

347

µITRON4.0 Specification

Ver. 4.00.00

348µITRON4.0 Specification

Ver. 4.00.00

Index
This is an index of the terms used in the main body of the µITRON4.0 Specification(Chapter 2 to Chapter 5). The number refers to the page where the term is defined or
explained.
A
activation (of task) ...................................................................................................53
activation request count ...........................................................................................79
active states ..............................................................................................................53
alarm handler .........................................................................................................250
API ...........................................................................................................................24
argument ..................................................................................................................25
atomicity (of service call) ........................................................................................64
attachment (of object) ..............................................................................................73
automatic assignment header file ............................................................................26
automatic ID number assignment (by configurator) ...............................................34
automatic ID number assignment (by service call) .................................................73
Automotive Control Profile ...................................................................................308
Bbase priority .............................................................................................................79
blocked state ............................................................................................................52
C
callback ....................................................................................................................24
calling message (of rendezvous) ...........................................................................193
configurator .............................................................................................................32
constant ....................................................................................................................26
context .....................................................................................................................51
CPU exception handler ....................................................................................60, 297
CPU locked state .....................................................................................................64
CPU state .................................................................................................................64
CPU unlocked state .................................................................................................64
creation (of object) ............................................................................................27, 73
current priority .........................................................................................................79
cyclic handler .........................................................................................................240
Ddata queue ..............................................................................................................145
data type ...................................................................................................................25
definition (of object) ................................................................................................27349

µITRON4.0 Specification

Ver. 4.00.00

delayed execution (of service call) ..........................................................................70
delayed state ..........................................................................................................111
deletion (of object) ..................................................................................................73
dispatch pending state .............................................................................................67
dispatcher ................................................................................................................51
dispatching ..............................................................................................................51
dispatching disabled state ........................................................................................66
dispatching enabled state .........................................................................................66
dispatching state ......................................................................................................66
DORMANT state ....................................................................................................53
E
error class ................................................................................................................28
error code .................................................................................................................28
eventflag ................................................................................................................134
extended information ...............................................................................................30
extended service call .............................................................................................292
extended service call routine ...........................................................................62, 292
F
FCFS ........................................................................................................................55
fixed-sized memory pool .......................................................................................214
function code ...........................................................................................................28
G
general constant expression parameter ....................................................................35
glue routine (for CPU exception handler) ...............................................................60
glue routine (for interrupt handler) ..........................................................................57
H
header file ................................................................................................................26
I
ID number ...............................................................................................................26
implementation-defined ..........................................................................................23
implementation-dependent ......................................................................................23
implementation-specific ..........................................................................................23
initialization routine ........................................................................................72, 297
insufficient resource error class ...............................................................................45
integer parameter .....................................................................................................35
integer parameter with automatic assignment .........................................................34
integer parameter without automatic assignment ....................................................34
internal error class ...................................................................................................44350

µITRON4.0 Specification

Ver. 4.00.00

internal identifier .....................................................................................................41
interrupt ...................................................................................................................57
interrupt handler ..............................................................................................57, 279
interrupt handler number .........................................................................................59
interrupt number ......................................................................................................59
interrupt service routine ...................................................................................57, 279
invoking context error class .....................................................................................45
invoking task ...........................................................................................................51
IRC ..........................................................................................................................57
ITRON general concepts, rules, and guidelines ......................................................23
ITRON general constant ..........................................................................................44
ITRON general data type .........................................................................................41
ITRON general macro .............................................................................................48
ITRON general static API .......................................................................................48
K
kernel configuration constant ..................................................................................75
kernel configuration macro ......................................................................................75
Lloose standardization .............................................................................................305
M
macro .......................................................................................................................26
mailbox ..................................................................................................................158
main error code ..................................................................................................28, 44
memory pool ..........................................................................................................214
message buffer .......................................................................................................181
message header ......................................................................................................158
message packet ......................................................................................................158
mutex .....................................................................................................................170
N
nesting (of task suspention requests) .....................................................................101
non-blocking ............................................................................................................31
NON-EXISTENT state ............................................................................................53
non-kernel interrupt .................................................................................................58
non-local jump .......................................................................................................114
non-task contexts .....................................................................................................62O
object .......................................................................................................................26
object attribute .........................................................................................................30351

µITRON4.0 Specification

Ver. 4.00.00

object number ..........................................................................................................27
object state error class .............................................................................................46
overrun handler .....................................................................................................258
P
packet ......................................................................................................................25
parameter .................................................................................................................25
parameter error class ...............................................................................................45
pending exception code .........................................................................................112
polling ......................................................................................................................31
precedence ...............................................................................................................51
precedence (between processing units) ...................................................................63
precedence (between tasks) .....................................................................................55
preempt ....................................................................................................................53
preprocessor constant expression parameter ...........................................................35
priority .....................................................................................................................27
priority (of task) ......................................................................................................79
priority ceiling protocol .........................................................................................170
priority inheritance protocol ..................................................................................170
priority inversions .................................................................................................170
processing unit .........................................................................................................61
processor time limit ...............................................................................................258
processor time used ...............................................................................................258
profile rule .............................................................................................................305
Q
queueing (of task activation requests) .....................................................................79
queueing (of task wakeup requests) ......................................................................101
R
READY state ...........................................................................................................52
real time ...................................................................................................................32
registration (of object) .............................................................................................27
relative time .............................................................................................................32
release task from waiting .........................................................................................53
rendezvous .............................................................................................................193
rendezvous number ...............................................................................................194
rendezvous port .....................................................................................................193
restricted task .........................................................................................................308
restriction (of service call functionality) ...............................................................305
resume (of suspended task) .....................................................................................53
return message (of rendezvous) .............................................................................193352

µITRON4.0 Specification

Ver. 4.00.00

return parameter .......................................................................................................25
return value (of service call) ....................................................................................28
round-robin scheduling ....................................................................................55, 267
runnable state ...........................................................................................................52
RUNNING state ......................................................................................................52
S
scheduler ..................................................................................................................51
scheduling ................................................................................................................51
scheduling rule .........................................................................................................55
semaphore ..............................................................................................................125
service call ...............................................................................................................24
service calls for non-task contexts ...........................................................................69
service calls for task contexts ..................................................................................70
simplified priority control rule ..............................................................................171
sleeping state .........................................................................................................103
software component identifier .................................................................................36
Standard Profile .....................................................................................................306
start code (of task) ...................................................................................................79
state transitions (of task) ..........................................................................................53
static API .................................................................................................................24
static API process ....................................................................................................72
strict priority control rule .......................................................................................171
sub error code ..........................................................................................................28
subsetting (of service call functionalities) .............................................................305
SUSPENDED state ..................................................................................................52
suspension count ....................................................................................................101
system call ...............................................................................................................24
system configuration file .........................................................................................32
system object ...........................................................................................................27
system time ......................................................................................................32, 235
Ttask ...........................................................................................................................51
task contexts ............................................................................................................62
task control block (TCB) .......................................................................................116
task dispatcher .........................................................................................................51
task dispatching .......................................................................................................51
task exception code ................................................................................................112
task exception disabled state .................................................................................112
task exception enabled state ..................................................................................112
task exception handling routine .......................................................................60, 112
353

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task scheduler ..........................................................................................................51
task scheduling ........................................................................................................51
task state ..................................................................................................................52
termination (of task) ................................................................................................53
time event handler ...........................................................................................61, 235
time tick .................................................................................................................235
timeout .....................................................................................................................30transitive priority inheritance ................................................................................171
U
undefined .................................................................................................................23
unsupported error class ............................................................................................44
user object ...............................................................................................................27
V
variable-sized memory pool ..................................................................................224
W
waiting released error class .....................................................................................46
WAITING state .......................................................................................................52
WAITING-SUSPENDED state ...............................................................................52
wakeup request count ............................................................................................101
warning class ...........................................................................................................47354