Motion Control Standards

Frederick M. Proctor

John L. Michaloski

National Institute of Standards and Technology

100 Bureau Drive, Stop 8230

Gaithersburg, MD 20899-8230

Motion Control Standards Issues [3](#motion-control-standards-issues)

Breadth of Domain [3](#breadth-of-domain)

Market Dynamics [4](#market-dynamics)

Market Dominance through Standardization
[4](#market-dominance-through-standardization)

Formal Standardization [4](#formal-standardization)

The Standards Landscape [5](#the-standards-landscape)

Standards Bodies [5](#standards-bodies)

IEC and ISO [5](#iec-and-iso)

ANSI [6](#ansi)

ISA [6](#isa)

CEN and CENELEC [6](#cen-and-cenelec)

DIN [7](#din)

BSI [7](#bsi)

Standards [7](#standards)

IEC 61158 (Fieldbus) [7](#iec-61158-fieldbus)

ISO 11898 (CAN) [8](#iso-11898-can)

DeviceNet [9](#devicenet)

Smart Distributed System (SDS) [9](#smart-distributed-system-sds)

CANOpen [10](#canopen)

LonTalk [10](#lontalk)

Seriplex [11](#seriplex)

Profibus [11](#profibus)

ControlNet [12](#controlnet)

Interbus [13](#interbus)

AS-Interface [13](#as-interface)

SERCOS [13](#sercos)

MACRO [14](#macro)

IEC 62026 [15](#iec-62026)

EN 50325 [15](#en-50325)

EN 50170 [15](#en-50170)

EN 50254 [16](#en-50254)

Fieldbus Comparisons [16](#fieldbus-comparisons)

Standards Glossary [18](#standards-glossary)

# Introduction

Control of moving parts is basic to modern industry, supporting
applications as varying as food processing, medicine, and aerospace
manufacturing. Motion control has evolved from its origins in mechanical
devices for regulating and transforming engine power, into today's
computers ranging in size from tiny embedded chips to networks of
high-performance workstations. This evolution has enabled manufacturers
to cut costs and improve quality by integrating motion control into the
broader enterprise. Standards are playing an increasingly important role
in this integration.

The primary goal of standardization is to enable interoperability of
systems. These include physical equipment, such as motors, and also
software, such as enterprise resource management programs. Because
systems integration takes place vertically, so must standardization.

A problem faced today by users, vendors, and integrators of motion
control technology is the profusion of standards. Deciding which to
support needs to take into account technical requirements, market
realities, and industry trends. The purpose of this report is to
identify the issues in motion control standardization, and give an
overview of the standards landscape.

# Motion Control Standards Issues

## Breadth of Domain

Motion control is a broad domain that spans a variety of applications,
includes a wide range of technology, and is comprised of many different
functions. Application demands range from simple position control of a
single axis, through coordinated control of multiple axes, with cross
coupling, dynamic compensation, and integration with process parameters.
Motion control technology encompasses sensors for proximity, position,
velocity, acceleration, and force, and actuators such as AC/DC rotary
and linear motors, hydraulic or pneumatic pistons, piezoelectric or
magnetostrictive actuators, and micro-electro-mechanical system (MEMS)
devices. Motion control functionality ranges from control of the moving
device itself through current or other motive forces at the microsecond
time scale, through high-level programmed motion with time scales of
minutes or longer, and all the stages in between. These many dimensions
of motion control make standardization an unwieldy task, and the natural
tendency to focus on particular problem areas has led to a proliferation
of standards that are all related yet all different.

Table 1 shows motion control using conventional motors from the
functionality point of view, as a hierarchy topped by high-level
description of programmed motion and running down to the torque that
moves the motors. Note that this table is specific to motor control, and
does not apply to hydraulic cylinder control, for example. However, this
functional viewpoint can be applied generally, where the appropriate
functions are listed at each level.

  ----------- ---------------- ----------------------------------------------
  **Level**   **Function**     **Description**

  10          Program Control  Reading and interpreting a motion program

  9           Move Sequencing  Determining when a motion element should be
                               scheduled for execution

  8           Profile          Calculation of the move parameters
              Generation       

  7           Trajectory       Calculation of an incremental position along
              Update           the move profile

  6           Position Loop    Closed loop control that tracks the trajectory
                               point for a particular motor, and outputs a
                               signal proportional to rate of change of motor
                               motion

  5           Velocity Loop    Closed loop control that tracks the resulting
                               motor speed based on tachometer feedback

  4           Commutation      Generating signals to motor poles for motor
                               types that are not self-commutating

  3           Current Loop     Converting rate of change to motor current,
                               proportional to torque

  2           Power Switching  Generating PWM signals that achieve motor
                               torque

  1           Torque           That which moves the motor
  ----------- ---------------- ----------------------------------------------

Table 1. Hierarchy of Motion Control Functionality for Conventional
Motors.

## Market Dynamics

Low costs for industrial automation can be achieved by using commodity
hardware from the computing and communication markets. This is evidenced
by the high level of interest in networks such as Ethernet, Universal
Serial Bus (USB), and Firewire. The accompanying rapid pace of
development in the computing and communication market also means that
products will be available for desktop computers long before they appear
in industrial control systems. However, the trend toward adopting
desktop technology on the shop floor means that the industrial control
market may be poised to benefit more quickly than it has in the past.

## Market Dominance through Standardization

Examples from the computing and communication industry have shown that
vendors who offer up their proprietary solutions as standards reap the
benefits of increased market share. This is especially true when
established vendors align behind a single standard to position
themselves ahead of their competition. Initially this is to the end
user's advantage, but the reaction among those vendors left out is to
start a competing standard. The result is that the end users are no
better off than before. A consequence of this proliferation of standards
is the rise of users groups. One purpose of these groups is to decide
which of the many applicable standards their members will support
strategically. Effective user's groups often include suppliers so that a
reasonable agreement can be reached without causing turmoil in the
market.

## Formal Standardization

Formal standardization through national or international standards
bodies may be a route toward stability in the marketplace, but in some
cases it has the reverse effect. This is the case with official,
enforceable standards that are mandated by governments or other public
agencies. In these cases, suppliers of nonconforming technologies are at
a severe disadvantage. Recognizing this, standards bodies often write
official standards with parts that include several competing
technologies. This has the effect of leveling the market so that a
single company or country is not given undue dominance. Unfortunately,
it also means that end users who agree to a particular standard find
themselves with incompatible solutions, each a part of the standard but
no two which are interoperable.

# The Standards Landscape

## Standards Bodies

Through their committees, standards bodies initiate, develop,
disseminate for voting, publish, and maintain standards. They range from
national bodies, through regional bodies, to international bodies.
Typically, a national body participates in regional or international
bodies through a Technical Advisory Group (TAG).

### IEC and ISO

The International Electrotechnical Commission (IEC) is the world
organization that prepares and publishes international standards for all
electrical, electronic and related technologies. IEC membership consists
of more than 50 countries. The IEC's mission is to promote, through its
members, international cooperation on all questions of electrotechnical
standardization and related matters, such as the assessment of
conformity to standards, in the fields of electricity, electronics and
related technologies. The IEC charter embraces all electrotechnologies
including electronics, magnetics and electromagnetics, electroacoustics,
telecommunication, and energy production and distribution, as well as
associated general disciplines such as terminology and symbols,
measurement and performance, dependability, design and development,
safety and the environment.

The International Organization for Standardization (ISO) is a worldwide
federation of national standards bodies from some 130 countries, one
from each country. The mission of ISO is to promote the development of
standardization and related activities in the world with a view to
facilitating the international exchange of goods and services, and to
developing cooperation in the spheres of intellectual, scientific,
technological and economic activity. ISO's work results in international
agreements that are published as International Standards.

Both IEC and ISO are organized into Technical Committees (TC),
Subcommittees (SC), and Working Groups (WG) whose participants do the
work of standardization.

IEC and ISO are made up of members that are the national body most
representative of standardization in its country. Thus, only one body in
each country may be admitted to membership. The U.S. member body of IEC
and ISO is the American National Standards Institute (ANSI). ANSI
designates Technical Advisory Groups (TAG) whose primary purpose is to
develop and transmit the member's positions on activities and ballots.

IEC and ISO differ in that IEC focus on electrical standards, and ISO
focuses on mechanical standards. The difference between the two domains
has blurred since the advent of computers and related electronic data
standards. As a result, many standards are released with joint IEC/ISO
designations.

IEC and ISO standards are designated with the prefix IEC or ISO,
respectively, followed by the standard number.

Related Standards: ISO 11898 (CAN), IEC 61158 (Fieldbus), IEC 62026

Information: www.iec.ch, www.iso.ch

### ANSI

The American National Standards Institute (ANSI) is the administrator of
the United States voluntary standardization system. ANSI facilitates
development of American National Standards (ANSs) by establishing
consensus among qualified groups. ANSI is the sole U.S. representative
and dues-paying member of ISO and IEC, and accredits TAGs that serve
these organizations.

Related Standards: ANSI/ISA-S50.02 (Fieldbus), ANSI/EIA 709.1 (LonTalk)

Information: www.ansi.org

### ISA

ISA is an international, nonprofit, educational organization founded in
1947 as the Instrumentation Society of America, but now known as the
International Society for Measurement and Control. ISA fosters
advancement in the theory, design, manufacture, and use of instruments,
computers, and systems for measurement and control. ISA publishes
*Motion Control* magazine.

ISA is an ANSI-accredited standards developer and its SP50 Subcommittee
serves as the U.S. Technical Advisory Group for IEC SC65A/WG4, Interface
Characteristics.

ISA standards are designated with the prefix ISA, followed by the
standard number. ISA standards may be jointly published with ANSI or
other organizations.

Related Standards: ANSI/ISA-S50.02 (Fieldbus)

Information: www.isa.org

### CEN and CENELEC

CEN (the European Committee for Standardization) and CENELEC (the
European Committee for Electrotechnical Standardization) are the
European equivalents of ISO and IEC, respectively. They are official
standards bodies recognized by the European Commission, responsible for
publishing standards for the European market.

With CEN, a procedure formalized as the Vienna Agreement allows CEN to
decide case by case according to precise conditions to transfer the
execution of European standards to ISO. Otherwise, a CEN Technical
Committee is established with national delegations of experts convened
by CEN members. The CEN TC must take into account any relevant work in
ISO or elsewhere falling within its scope. The results of this work can
then be offered to ISO once the CEN standard is complete.

With CENELEC, proposed standards originating in Europe are offered to
IEC with the request that they be undertaken at international level. If
IEC does not want to undertake the work, or if it cannot meet the target
dates, the work commences at CENELEC for Europe. If IEC undertakes the
work, parallel IEC/CENELEC procedures aim at identical worldwide and
European standards. Once CENELEC work has commenced, all work on the
same subject that may be taking place in individual European nations is
immediately stopped.

CEN and CENELEC standards are designated with the prefix EN, followed by
the standard number.

Related Standards: EN 50170, EN 50254, EN 50295, EN 50325

Information: www.cenorm.be, www.cenelec.org

### DIN

Deutsches Institut für Normung (DIN) is the German standards body that
reports to CEN and CENELEC.

DIN standards are designated with the prefix DIN, followed by the
standard number.

Related standards: DIN 19245 (Profibus), DIN 19258 (Interbus-S)

Information: www.din.de

### BSI

The British Standards Institution (BSI) is the United Kingdom's official
standards making body. Independent of government, industry and trade
associations BSI is a non-profit distributing organization. BSI works
with manufacturing and service industries, businesses and governments to
facilitate the production of British, European and international
standards.

BSI standards are designated with the prefix DD, followed by the
standard number.

Related standards: DD 238 (Foundation Fieldbus), DD 241 (ControlNet)

Information: www.bsi.org.uk

## Standards

As a consequence of the breadth of the motion control domain, there is a
profusion of standards. This would not present a problem if each
standard covered a different part of motion control functionality, as
exemplified in Table 1, but this is not a case. The value of the motion
control and larger input/output device markets has led to companies
positioning themselves for market dominance by offering their protocols
as standards. As a result, there are incompatible standards that cover
equivalent areas, such as device networks. This causes problems for
buyers and suppliers alike. It is simply too costly to support all the
standards.

Formal standardization would seem to solve the problem, but in some
cases it has had the opposite effect. In Europe especially, where
conforming to a standard is often a contractual requirement for public
works projects, standards have arisen which simply include incompatible
industry standards. This makes the problem worse: two users may each
agree to use a single standard, but their systems will be incompatible.

### IEC 61158 (Fieldbus)

IEC 61158, "Fieldbus standard for use in industrial control systems," is
the culmination of over a decade's worth of efforts to standardize a
replacement for the analog 4-20 milliamp de facto standard for field
wiring of input/output devices. IEC 61158 is the result of the merging
of two previously incompatible fieldbus standards espoused by the
Interoperable Systems Project (ISP) and WorldFIP groups. IEC 61158 is
the responsibility of IEC Working Group SC65C, with the U.S. TAG IEC/ISA
SP50 subcommittee. The Fieldbus Foundation (FF) endorses IEC 61158 and
its conforming implementation, Foundation Fieldbus. FF membership is
comprised of over 120 suppliers and users of control and
instrumentation, including Fisher-Rosemount, Siemens, Honeywell, and
Elsag-Bailey.

IEC 61158 is divided into parts, following the ISO 7498 Open Systems
Interconnect (OSI) model for the Physical, Data Link, and Application
Layers. Part 2, the Physical Layer, was approved in 1993. Parts 3 and 4,
the Data Link Layer Services and Protocol, and Parts 5 and 6, the
Application Layer Services and Protocol, did not pass the latest IEC
vote. IEC SC65C has passed a ballot recommending disqualifying six
negative votes for being non-technical, but final approval of these
parts is still being sought.

Foundation Fieldbus is being standardized in the UK as DD 238.

The FF is expanding Foundation Fieldbus to support 100 megabit/second
high-speed Ethernet. The draft preliminary specifications were passed in
1998.

See Tables 2-4 for comparisons between fieldbus protocols.

Information: www.iec.ch, www.fieldbus.org, www.isa.org

### ISO 11898 (CAN)

ISO 11898, "Road vehicles- interchange of digital information-
controller area network (CAN) for high-speed communication)" was
originally developed by the Bosch Corporation for use in automobiles.
CAN is based on the ISO 7498 Open Systems Interconnect (OSI) model for
the Physical and Transport Layers. The standard does not specify an
Application Layer. CAN was approved as ISO 11898 in 1993.

CAN is a high-speed network, meeting the Society of Automotive Engineers
(SAE) Class C network requirements for 1 megabit/second data transfer
and 5 millisecond latency. CAN chips are available in high volumes from
manufacturers such as Phillips, Intel, and Motorola. The chips can be
interfaced to various transmission media, such as one-wire, two-wire, or
fiber optic.

CAN is a multi-master network, where the bus access arbitration is based
on the message identifier. The message identifier is 11 bits, supporting
2048 messages. An extended message identifier of 29 bits was introduced
to allow a larger number of messages. The data field of messages can be
up to 8 bytes wide. Messages that require larger data fields must be
sent in segments. CAN messages use 16-bit cyclic redundancy checking
(CRC-16) for error detection and correction. With a full 8-byte data
message, the data to message size is 57%, with the rest consisting of
overhead for the message identifier, control, and framing bits.

CAN data rates depend on trunk distance: 1 megabit/second for up to 40
meter distances, 125 kilobits/second for up to 500 meter distances, and
50 kilobits/second for up to 1 kilometer.

The standard lacks an Application Layer protocol, which has led to its
use in a variety of applications other than automobiles, including
industrial automation, medical equipment, and building automation.
Developing an application layer for industrial automation on top of the
CAN protocol is the subject of numerous industrial and formal standards
projects, including DeviceNet, Smart Distributed System (SDS), and
CANOpen.

### DeviceNet

DeviceNet, like CANOpen and SDS, is an application layer on top of CAN,
advocated by the Open DeviceNet Vendors Association (ODVA). DeviceNet
was originally developed by Allen-Bradley, but is now an open standard
that may be obtained from the ODVA. Any company manufacturing DeviceNet
products may join ODVA and participate in technical working groups that
are developing enhancements to the DeviceNet Specification. Buyers of
the DeviceNet Specification receive an unlimited, royalty-free license
to develop DeviceNet products. The ODVA is comprised of over 300
members, including ABB, Cutler-Hammer, GE Fanuc, and Rockwell
Automation/Allen-Bradley.

The DeviceNet specification includes Volume 1, the Application Layer,
and Volume 2, Device Profiles. The Application Layer adds to the CAN bus
the concepts of connections, and data transfer models including strobed,
polled, cyclic, change-of-state, and application-triggered. Device
addressing may be peer-to-peer with multicast, multi-master, or
master-slave. Device Profiles promote interoperability by defining
standard device models that support common identification and status
data. Device profiles contain a definition of the device object model, a
list of the object classes present in the device, definitions of data
formats, and definitions of configurable parameters. The DeviceNet
object model organizes the attributes, services, and behaviors of a
product.

The DeviceNet specification is more specific than the standard CAN
protocol with respect to some physical properties. These include
allowable topologies, system grounding, use of thick and thin media,
termination, and power distribution. The DeviceNet trunkline-dropline
topology provides separate twisted pair buses for both signal and power
distribution. Up to 64 addressable nodes are supported. See Tables 2-4
for details on DeviceNet and comparisons with other protocols.

Information: www.devicenet.org

### Smart Distributed System (SDS)

Smart Distributed System (SDS), like CANOpen and DeviceNet, is an
application layer on top of the CAN bus. SDS was introduced by Honeywell
Micro Switch in early 1993 and formally opened to other vendors the
following year. The SDS specification is currently under engineering
control of the SDS Council.

SDS specifies an Application Layer, Component Model, and a Physical
Layer. The Application Layer specifies services, such as read, write,
event generation and handling, and connection establishment for
multicast or peer-to-peer communication. The Application Layer also
includes protocols that define data and message types.

The Component Model Specification defines a hierarchical object-oriented
view of devices and their relationships.

The Physical Layer restricts the CAN physical layer specification. SDS
transmission speeds of 125K, 250K, 500K, and 1.0M bits/sec allow network
lengths of 1,500, 600, 300, and 75 feet, respectively. The trunk
consists of two-wire twisted shielded cable with optional two-wire bus
power cable and drain wire. There is a maximum of 32 nodes at 1.0M
bits/sec and 64 nodes at the lower transmission speeds. See Tables 2-4
for details on SDS and comparisons with other protocols.

Information: honeywell1.datareturn.com/sensing/prodinfo/sds

### CANOpen

CANOpen, like DeviceNet and SDS, is an application layer on top of CAN,
advocated by the CAN in Automation (CiA) group based in Germany. CANOpen
builds on the Physical and Transport Layers of CAN in a family of
profiles that consists of the Application Layer and Communication
Profile (CiA DS 301), various frameworks and recommendations (CiA
DS-30x), and various device profiles (CiA DS-40x).

The DS 301 Application Layer and Communication Profile defines how data
is exchanged between devices and describes the interface to the
underlying communication medium, including which data has to be
transmitted and with which services.

The DS-40X device profiles aid systems integration and device
standardization by specifying guidelines by which two independent
manufacturers can produce standardized devices. Guidelines include
mandatory device characteristics that guarantee correct network
operation, and a profiling mechanism that allows manufacturers to
provide options and future enhancements. Device profiles include digital
and analog I/O modules, motor drives, encoders, motion controllers, and
operator displays.

Information: www.canopen.de

### LonTalk

LonTalk is the protocol underlying Echelon Corporation's LonWorks
control networks, approved in 1999 as an ANSI standard, ANSI/EIA
709.1-A-1999, and is Part 4 of IEC 62026. LonTalk can be implemented on
a variety of microcontrollers and microprocessors, and are built in to
Neuron chips, microcontrollers optimized for intelligent distributed
control applications that are manufactured by Cypress Semiconductor and
Toshiba Corporation.

LonWorks nodes implement the LonTalk protocol, connect to the physical
communication medium, and perform control functions specific to the
device. Devices such as proximity sensors, switches, motion detectors,
relays, motor drives, and instruments, may all be nodes on the network.
Local Control Nodes are network devices that control the operation of
attached sensors and/or actuators based on local and network events.
Supervisory Nodes are network devices that collect and log data from one
or more local control nodes, or coordinate the operation of one or more
local control nodes. Routers provide transparent connectivity between
two LonWorks network channels.

See Tables 2-4 for details on LonTalk and comparisons with other
protocols.

Information: www.echelon.com/protocol

### Seriplex

Seriplex (Serial Multiplexed Control Bus) is an industrial control bus
developed by Automated Process Control and patented in 1987. The
Seriplex Technology Organization (STO) is an independent, non-profit
corporation, created to support and promote Seriplex Control Bus
technology in the general marketplace. Seriplex is Part 5 of
international standard IEC 62026.

Seriplex is a deterministic, serial multiplexed, intelligent,
distributed I/O system, providing both master/slave and peer-to-peer I/O
control and logic. It uses a shielded four-conductor cable. Two of the
conductors deliver +12 VDC power or +24 VDC power to the bus. The other
two conductors provide the data signal and clock signal that controls
network timing.

Seriplex networks consist of I/O devices with integrated Seriplex chips,
or an I/O block with a Seriplex chip into which devices are wired. In
Master/Slave mode, the chip provides for the communication of I/O device
events to a host CPU. In Peer-to-Peer mode, there is no host CPU. Events
occurring at each device are communicated directly between I/O blocks or
devices containing an embedded chip. These events are acted upon at the
device level and are based on the logic functions programmed into the
chips. See Tables 2-4 for details on Seriplex and comparisons with other
protocols.

Information: www.seriplex.org

### Profibus

Profibus (Process Field Bus) is a fieldbus standard for integrating
sensors, actuators, transmitters, drives and programmable logic
controllers. The Profibus User Organization (PNO) is the sponsoring
organization, representing manufacturing, users, and systems integrators
of Profibus components. Profibus consists of three specifications:
Profibus-FMS, Profibus-DP, and Profibus-PA. Profibus-FMS and Profibus-DP
are Volume 2 of European standard EN 50170.

The Profibus-FMS (Fieldbus Message Specification) is designed for
acyclic or cyclic data transfers at medium speed between control
equipment and cell-level controllers.

Profibus-DP is a performance optimized version of Profibus specifically
dedicated to time-critical communication between automation systems and
distributed peripherals. It is designed as a replacement for discrete
wiring of 24 V and 4 to 20 mA measurement signals.

Profibus-PA (Process Automation) is designed specifically for the needs
of the process automation industry. Profibus-PA provides for power and
data transmission over the same two wires, and can be used within areas
with high explosion risk using intrinsic safe transmission technology
according to IEC 1158-2. It operates either with intrinsic safe
transmission technology (IEC 1158-2) or standard transmission technology
(RS-485).

Profibus specifies the lowest two levels of the OSI protocol stack, the
Physical and Data Link Layers. Additionally, Profibus-FMS specifies the
Application Layer, the topmost (Level 7), using a subset of the
Manufacturing Message Specification (MMS) (ISO 9506) of the MAP
protocol.

The physical layer uses copper wire in accordance with the US standard
EIA RS-485. It uses a two-conductor twisted pair cable, with optional
shielding. Two cable versions with different maximum distances are
available. A specification for fiber optic transmission for longer
length and noise immunity is being proposed.

Profibus uses the token passing method for communication between complex
stations (masters) and the master-slave method for communication between
complex stations and simple peripheral devices (slaves). This combined
method is called hybrid medium access. With the hybrid medium access
method of Profibus it is possible to implement a pure master-slave
system, a pure master-master system (token passing), and a system with a
combination of both methods.

See Tables 2-4 for details on Profibus and comparisons with other
protocols.

Information: www.profibus.com

### ControlNet

ControlNet is a device network developed by Rockwell/Allen-Bradley and
made available as an open standard in 1996. ControlNet is designed for
real-time, high-speed integration of control systems such as coordinated
drive systems, weld control, motion control, vision systems, complex
batch control systems, process control systems, and systems with
multiple controllers and human-machine interfaces. ControlNet targets
systems with multiple PC-based Controllers, PLC-to-PLC and PLC-to-DCS
communication.

ControlNet views industrial application as consisting of three layers.
The information layer supports plant-wide data collection and program
maintenance, and uses protocols such as Ethernet. The automation and
control layer supports real-time I/O control, interlocking, and
messaging, and is the target for ControlNet. The device layer supports
cost-effective integration of individual devices, and it uses fieldbus
protocols such as DeviceNet or Foundation Fieldbus.

ControlNet International, an independent organization for users and
vendors of ControlNet products, was formed in July 1997. The
organizations manages the ControlNet Specification and supports
worldwide growth of ControlNet by developing test software, providing
independent compliance testing, publishing the ControlNet product
catalog, and sponsoring design and implementation training.

ControlNet supports a maximum data transfer of 5.0 megabit/second using
coaxial cable or fiber optic transmission media. Devices are powered
externally. There is a limit of 99 addressable nodes, but no limit on
the number of I/O data points that can be integrated.

ControlNet is based on a producer/consumer communication model. This
model permits all nodes on the network to simultaneously access the same
data from a single source. Network access is controlled by a time-slice
algorithm called Concurrent Time Domain Multiple Access (CTDMA), which
regulates a node's opportunity to transmit in each network interval,
which is configurable and can be as small as 2 milliseconds.

ControlNet was standardized in Europe in 1998 as Amendment A3 to EN
50170, and is being standardized in the UK as DD 241.

Information: www.controlnet.org

### Interbus

Interbus was developed in 1984 by Phoenix Contact and approved as German
standard DIN 19258. Interbus is promoted by the Interbus Club, a
member-funded, non-profit organization established to maintain and
advance the Interbus network standard. The Interbus Club was initially
founded in Europe in 1993. Currently there are over 600 members in 15
countries.

Interbus is a master-slave hardware ring network with cabling options
that allow for twisted pair or fiber optic transmission media. The data
link layer supports full duplex communication with no arbitration and
CRC error correction. Interbus supports up to 512 devices and a total of
4096 digital input and 4096 digital output points or combinations of
digital and analog signal types. Interbus is commonly implemented using
the RS-485 serial digital protocol with a five-wire cable.

See Tables 2-5 for details on Interbus and comparisons with other
protocols.

Information: www.interbus.com, www.ibsclub.com

### AS-Interface

EN 50295, "Low-voltage switchgear and controlgear- controller and device
interface systems- actuator sensor interface (AS-Interface)," or AS-I,
is a European standard carried out by CENELEC technical committee TC17B.
AS-i was approved in 1998.

AS-I was designed as a low-cost alternative to more complex fieldbuses,
suitable for networking simple binary devices. AS-I (often pronounced
"azzi") uses a single yellow cable that contains both data and power.

Power comes from a 24V DC supply that is fully isolated from the data
signals. Data is modulated to ensure noise immunity. The network is
typically rated up to 8A, but higher currents can be drawn provided
voltage drops in the network conform to the specification. A separate
black cable and power supply can be used if needs demand it.

Each AS-Interface network has one master and can include up to 31 slave
devices. Slaves can connect up to four devices, supporting 124 inputs
and 124 outputs. Slaves are polled by the master at a frequency of
167kHz, giving a maximum latency of 5ms on a fully loaded network. Cycle
times are faster with fewer devices. Network messages have four data
bits that may be used as inputs or outputs, so that AS-I can be used for
analog devices by splitting data across cycles. In addition to data
bits, the protocol transmits other information, such as status bits that
can be used for diagnostics. See Tables 2-4 for details on AS-I and
comparisons with other protocols.

Information: www.as-interface.com

### SERCOS

SERCOS (Serial Realtime Communication System) is a digital interface for
communication between control systems and drives. SERCOS was approved as
international standard IEC 61491 in 1995 and as European standard EN
61491 in 1998. The SERCOS specification includes the physical layer,
including connectors. An optical fiber ring is used as transmission
medium. The maximum transmission rate is 2, 4, 8 or 16 megabit/second,
depending on the device design. Three communications types between CNC
and digital drive control elements can be realized with this interface:
nominal position, nominal speed, or nominal torque. The transmission of
nominal position is the recommended type for fast and highly precise
applications.

In one optical fiber ring up to 6 axes can be cyclically and parallel
supplied with new nominal positions values (nominal positions) every 0.5
ms. The SERCOS interface allows all drive-internal data, parameters and
diagnosis data to be displayed and entered by means of a
SERCOS-compatible CNC.

All drives on the SERCOS ring close loops synchronously, eliminating the
possibility of "beat" frequencies or harmonics appearing in the motion
control system. Feedback acquisition and command value executions are
performed in every drive at the same instant in time, making an
effective "snapshot" for control purposes.

Each segment (node-to-node) of a SERCOS ring can be up to 40 meters in
length using plastic fiber, 200 meters using 200 µm glass fiber, or 400
meters using 400 µm glass fiber. Total ring lengths are 10,000 meters,
50,000 meters and 100,000 meters respectively.

The maximum number of drops per fiber optic ring is 254. However, the
number of drives that can be serviced per ring depends on three
application requirements: communication cycle time, volume of
operational data, and communications speed required. SERCOS imposes no
limit to the number of rings that can be synchronized together.

Information: www.sercos.org, www.sercos.com

### MACRO

MACRO (Motion And Control Ring Optical) is a specification for
connecting multi-axis motion controllers, amplifiers, and I/O over a
single high speed fiber optic network. MACRO uses fiber optic or RJ-45
"thin wire" interfaces. The fiber optic interface allows the drives to
be up to 1 kilometer from the drive to the controller, and the RJ-45
interface allows the drives to be up to 1,000 feet from the controller.
MACRO's fiber optic interface technology provides total electrical noise
immunity. MACRO communicates at 125 megabits a second.

MACRO operates in a ring topology. Data is transmitted serially. Each
station on the ring has an "in" port for receiving data and an "out"
port for transmitting data. Nodes, residing at a station, can be
amplifier axes, I/O banks, or communication interfaces to other devices.
A station can have one or several nodes, allowing for multi-axis
amplifiers with a single "in" and single "out" port. Data packets,
(groups of 96 bits of serial data), sent out by a motion controller or,
master node, are earmarked for a specific amplifier, or slave node. If
the data packet is not for an amplifier, it passes it on, unchanged. If
it is for the node, it copies the contents of the data packet (typically
commands), places feedback data into the packet in place of the command
data, and transmits the data packet.

Building MACRO into a product requires the MACRO gate array integrated
circuit. Currently the gate array is available from Delta Tau Data
Systems in 144 or 160 pin QFP packages and is designed for a 24 bit
microcontroller.

Information: www.deltatau.com/dtmacro7.htm

### IEC 62026

IEC 62026, "Control circuit devices and switching elements for
low-voltage switchgear and controlgear," provides official international
standards status to five device networks: AS-i, DeviceNet, Lontalk, SDS,
and Seriplex.

IEC 62026 is divided into six parts. Some of these parts are technically
equivalent to other standards:

-   Part 1, General Requirements (EN 50325-1)

-   Part 2, AS-I (EN 50295)

-   Part 3, DeviceNet (EN 50325-2)

-   Part 4, Lontalk (ANSI/EIA 709.1)

-   Part 5, SDS (EN 50325-3)

-   Part 6, Seriplex

Information: www.iec.ch

### EN 50325

EN 50325, "Industrial communication subsystem based on ISO 11898 (CAN)
for controller-device interfaces," is a proposed European standard being
carried out by CENELEC technical committee TC65CX. EN 50325 provides
official European standards status to two CAN-based application layer
protocols: DeviceNet and Smart Distributed System (SDS).

EN 50325 is divided into volumes, some of which are technically
equivalent to parts of international standard IEC 62026:

-   Volume 1, General

-   Volume 2, DeviceNet (IEC 62026-3)

-   Volume 3, SDS (IEC 62026-5)

Information: www.cenelec.org

### EN 50170

EN 50170, "General purpose field communication systems," is a European
standard for fieldbuses that was made enforceable by the European
Commission for utilities and other public undertakings. EN 50170 was
approved in 1997, and originally conferred standards status on three
fieldbuses: P-Net (Denmark), Profibus-DP/FMS (Germany), and WorldFIP
(France). The UK proposed adding Foundation Fieldbus, Profibus-PA, and
ControlNet as amendments, so that these fieldbuses (and companies that
sold them) would not be left out. EN 50170 is comprised of the following
parts and amendments, some of which are equivalent to other standards:

-   Volume 1, P-Net (DK 502058, 502066)

-   Volume 2, Profibus-DP/FMS (DIN 19245)

-   Volume 3, WorldFIP (NFC 46601-46607)

-   Amendment A1, Foundation Fieldbus (DD 238)

-   Amendment A2, Profibus-PA

-   Amendment A3, ControlNet (DD 241)

Information: www.cenelec.org

### EN 50254

EN 50254, "High efficiency communication subsystem for small data
packages," is a downsizing of EN 50170 for applications with smaller
data size and lower data rates. It includes subsets of Profibus-DP and
WorldFIP, and adds Interbus-S:

-   Volume 1, General

-   Volume 2, Interbus-S (DIN 19258)

-   Volume 3, Profibus-DP (EN 50170-2)

-   Volume 4, WorldFIP/1 (EN 50170-3)

## Fieldbus Comparisons

Tables 2 through 4 show the general information, physical
characteristics, and transport mechanism of specific standards covered
in this document. See also:

http://www.synergetic.com/compare.htm

http://www.ibsclub.com/whyibus/comparisons

  --------------- --------------- ------------ ---------------- ----------------
  **BACKGROUND                                                  
  INFORMATION**                                                 

                  Technology\     Year\        Governing\       Openness
                  Developer       Introduced   Standard         

  AS-I            AS-I Consortium Fall 1993    Submitted to IEC AS-II.C. Market
                                                                item

  DeviceNet       Allen-Bradley   March 1994   ISO 11898 &      6 chip vendors,
                                               11519            300+ products

  Fieldbus        Fieldbus        1995         ISA SP50/IEC     Chips/software
  Foundation      Foundation                   TC65             from multiple
                                                                vendors

  Interbus        Phoenix Contact 1984         EN50254          2000 Products
                                                                from over 1000
                                                                manufacturers

  LonTalk         Echelon Corp.   March 1991   ASHRAE of BACnet Public
                                                                documentation on
                                                                protocol

  Profibus\       Siemans/PTO     DP-1994,\    DIN 19245 part ¾ Products from
  DP/PA                           PA-1995                       over 1400
                                                                vendors

  SDS             Honeywell       Jan. 1994    Honeywell        6 chip vendors,
                                               Specification,   200+ products
                                               Submitted to     
                                               IEC, ISO11989    

  Seriplex        APC, Inc.       1990         Seriplex spec    Chips available\
                                                                multiple
                                                                interfaces

  WorldFIP        WorldFIP        1988         IEC 1158-2       Multiple chip
                                                                vendors
  --------------- --------------- ------------ ---------------- ----------------

*Table 2. Background Information.*

  ------------------- -------------------- --------------- ---------------- ----------
  **PHYSICAL                                                                
  CHARACTERISTICS**                                                         

                      Network\             Physical\       Max. Devices\    Max.\
                      Topology             Media           (nodes)          Distance

  AS-I                Bus, ring, tree star Two wire cable  31 slaves        100
                                                                            meters,
                                                                            300 with
                                                                            repeater

  DeviceNet           Trunkline/dropline   Twisted-pair    64 nodes         500m
                      with branching       for signal &                     
                                           power                            

  Fieldbus Foundation Multidrop with bus   Twisted-pair    240/segment,     1900m @
                      powered devices                      65,000 segments  31.25K
                                                                            500m @
                                                                            2.5M

  Interbus            Open: Bus,Tree,      Twisted-pair,   512 System       12.8 Km
                      Ring, Star, 16 level fiber,          Total\           (copper)
                      nesting              slip-ring,      256 on remote    total\
                                           Infrared        bus              400m max
                                                                            between
                                                                            devices

  LonTalk             Bus, ring, loop,     Twisted-pair,   32,000/domain    2000m @ 78
                      star                 fiber, power                     kbps
                                           line                             

  Profibus DP/PA      Line, star & ring    Twisted-pair or 127 nodes        24 Km
                                           fiber                            (fiber)

  SDS                 Trunkline/Dropline   Twisted-pair    64 nodes, 126    500m
                                           for signal &    addresses        
                                           power                            

  Seriplex            Tree, loop, ring,    4-wire shielded 500+ devices     500+ ft.
                      multi-drop, star     cable                            

  WorldFIP            Bus                  Twisted-pair,   256 nodes        up to 40
                                           fiber                            Km
  ------------------- -------------------- --------------- ---------------- ----------

*Table 3. Physical Characteristics.*

+-------------+----------+--------+--------+--------+-------+-------+
| **TRANSPORT |          |        |        |        |       |       |
| MECHANISM** |          |        |        |        |       |       |
+-------------+----------+--------+--------+--------+-------+-------+
|             | Commun   | T      | Data\  | Arbitr | E     | D     |
|             | ication\ | ransmi | Tra    | ation\ | rror\ | iagno |
|             | Method   | ssion\ | nsfer\ | Method | Che   | stics |
|             |          | Prop   | Size   |        | cking |       |
|             |          | erties |        |        |       |       |
+-------------+----------+--------+--------+--------+-------+-------+
| AS-I        | Mast     | Data   | 31     | Master | Manch | Slave |
|             | er/slave | and    | slaves | /slave | ester | f     |
|             | with     | power, | with 4 | with   | Code, | ault\ |
|             | cyclic   | EMI    | in and | cyclic | hammi | d     |
|             | polling  | res    | 4 out  | p      | ng-2, | evice |
|             |          | istant |        | olling | p     | fault |
|             |          |        |        |        | artly |       |
+-------------+----------+--------+--------+--------+-------+-------+
| DeviceNet   | Maste    | 500    | 8-byte | C      | CRC   | Bus   |
|             | r/slave, | kbps,  | va     | arrier | check | monit |
|             | multi    | 250    | riable | -Sonac |       | oring |
|             | -master, | kbps,  | m      | Mu     |       |       |
|             | others   | 125    | essage | ltiple |       |       |
|             |          | kbps   |        | Access |       |       |
+-------------+----------+--------+--------+--------+-------+-------+
| Fieldbus    | Clien    | 31.25  | 16.6 M | D      | 1     | R     |
| Foundation  | t/server | kbps 1 | ob     | etermi | 6-bit | emote |
|             | publi    | Mbps\  | jects/ | nistic | CRC   | di    |
|             | sher/sub | 2      | device | centr  |       | agnos |
|             | scriber, | .5Mbps |        | alized |       | tics, |
|             | Event    |        |        | sche   |       | ne    |
|             | noti     |        |        | duler, |       | twork |
|             | fication |        |        | mu     |       | moni  |
|             |          |        |        | ltiple |       | tors, |
|             |          |        |        | backup |       | para  |
|             |          |        |        |        |       | meter |
|             |          |        |        |        |       | s     |
|             |          |        |        |        |       | tatus |
+-------------+----------+--------+--------+--------+-------+-------+
| Interbus    | Mast     | 500kB  | Up to: | None   | 1     | Wire  |
|             | er/slave | its/s, |        |        | 6-bit | loc   |
|             | with     | full   | 6      |        | CRC   | ation |
|             | total    | duplex | 4bytes |        | be    | of    |
|             | frame    |        | real   |        | tween | CRC   |
|             | transfer |        | time   |        | each  | error |
|             |          |        | data   |        | d     | and   |
|             | Tra      |        | /d     |        | evice | cable |
|             | nsparent |        | evice, |        |       | b     |
|             | data     |        |        |        |       | reak\ |
|             | linking  |        | 244    |        |       | M     |
|             | via      |        | Bytes  |        |       | odule |
|             | master   |        | PCP    |        |       | & I/O |
|             |          |        | data/  |        |       | ch    |
|             |          |        | device |        |       | annel |
|             |          |        |        |        |       | d     |
|             |          |        | 512    |        |       | iagno |
|             |          |        | In +   |        |       | stics |
|             |          |        | 512    |        |       |       |
|             |          |        | Out    |        |       |       |
|             |          |        | bytes  |        |       |       |
|             |          |        | per    |        |       |       |
|             |          |        | system |        |       |       |
+-------------+----------+--------+--------+--------+-------+-------+
| LonTalk     | Maste    | 1.25   | 228    | C      | 1     | Dat   |
|             | r/slave\ | Mbs    | bytes  | arrier | 6-bit | abase |
|             | peer to  | full   |        | Sense, | CRC   | of    |
|             | peer     | duplex |        | Mu     |       | CRC   |
|             |          |        |        | ltiple |       | e     |
|             |          |        |        | Access |       | rrors |
|             |          |        |        |        |       | and   |
|             |          |        |        |        |       | d     |
|             |          |        |        |        |       | evice |
|             |          |        |        |        |       | e     |
|             |          |        |        |        |       | rrors |
+-------------+----------+--------+--------+--------+-------+-------+
| Profibus    | Maste    | DP up  | 244    | Token  | HD4   | Sta   |
| DP/PA       | r/slave\ | to 12  | bytes  | p      | CRC   | tion, |
|             | peer to  | Mbps\  |        | assing |       | m     |
|             | peer     | PA     |        |        |       | odule |
|             |          | 31.25  |        |        |       | &     |
|             |          | kbps   |        |        |       | ch    |
|             |          |        |        |        |       | annel |
|             |          |        |        |        |       | d     |
|             |          |        |        |        |       | iagno |
|             |          |        |        |        |       | stics |
+-------------+----------+--------+--------+--------+-------+-------+
| SDS         | Maste    | 1      | 8-byte | C      | CRC   | Bus   |
|             | r/slave, | Mbps,\ | va     | arrier | check | m     |
|             | peer to  | 500    | riable | -Sonac |       | onito |
|             | peer,    | kbps,\ | m      | Mu     |       | ring, |
|             | mul      | 250    | essage | ltiple |       | Diagn |
|             | ti-cast, | kbps,\ |        | Access |       | ostic |
|             | mult     | 125    |        |        |       | slave |
|             | i-master | kbps   |        |        |       |       |
+-------------+----------+--------+--------+--------+-------+-------+
| Seriplex    | Mast     | 200    | 7      | Sonal  | End   | Ca    |
|             | er/slave | Mbps   | 680/tr | multip | of    | bling |
|             | peer to  |        | ansfer | lexing | frame | pro   |
|             | peer     |        |        |        | &     | blems |
|             |          |        |        |        | echo  |       |
|             |          |        |        |        | check |       |
+-------------+----------+--------+--------+--------+-------+-------+
| WorldFIP    | Peer to  | 31.25  | No     | C      | 1     | D     |
|             | peer     | kbps,  | limit, | entral | 6-bit | evice |
|             |          | 1 &    | var    | arbit  | CRC,  | me    |
|             |          | 2.5    | iables | ration | data  | ssage |
|             |          | Mbps,  | 128    |        | "     | time  |
|             |          | 6 Mbps | bytes  |        | fresh | -out, |
|             |          | fiber  |        |        | ness" | redu  |
|             |          |        |        |        | indi  | ndant |
|             |          |        |        |        | cator | ca    |
|             |          |        |        |        |       | bling |
+-------------+----------+--------+--------+--------+-------+-------+

*Table 4. Transport Mechanisms.*

# Standards Glossary

ANSI/EIA 709.1 LonTalk

DD 238 Foundation Fieldbus

DD 241 ControlNet

DIN 19258 Interbus-S

DIN 19425 Profibus

EN 50170 General purpose field communication systems. Includes P-Net,
Profibus-DP/FMS/PA, WorldFIP, Foundation Fieldbus, and ControlNet.

EN 50254 High-efficiency communication subsystem for small data
packages. Includes Interbus, Profibus-DP subset, and WorldFIP subset.

EN 50295 Low-voltage switchgear and controlgear- controller and device
interface systems- actuator sensor interface (AS-I).

EN 50325 Industrial communication subsystem based on ISO 11898 (CAN) for
controller-device interfaces. Includes DeviceNet and SDS.

EN 61491 SERCOS

IEC 1158-2 Specification for intrinsically safe operation

IEC 61158 Digital data communications for measurement and control-
Fieldbus for use in industrial control systems

IEC 61491 SERCOS

IEC 62026 Control circuit devices and switching elements for low-voltage
switchgear and controlgear. Includes AS-I, DeviceNet, LonTalk, SDS, and
Seriplex.

IEC SC65C IEC Subcommittee responsible for IEC 61158 (Fieldbus).

IEEE 802.2 Ethernet

IEEE 802.3u Request for Change (RFC) for TCP/IP and UDP, in support of
Foundation Fieldbus HSE

ISA SP50 ISA Subcommittee responsible for ANSI/ISA-S50.02 (Fieldbus).

ANSI/ISA-S50.02 Fieldbus Standard for use in Industrial Control Systems.
U. S. equivalent of ISO 61158.

ISO 7498 Open Systems Interconnect (OSI) 7-layer model for communication

ISO 9506 Manufacturing Messaging Specification (MMS), used by
Profibus-FMS.

ISO 11519 DeviceNet

ISO 11898 Road vehicles- interchange of digital information- controller
area network (CAN) for high-speed communication. Defines physical and
transport layers. DeviceNet, SDS, and CANOpen add application layer.

**Disclaimer**

No approval or endorsement of any commercial product by the National
Institute of Standards and Technology is intended or implied. Certain
commercial equipment, instruments, or materials are identified in this
report in order to facilitate understanding. Such identification does
not imply recommendation or endorsement by the National Institute of
Standards and Technology, nor does it imply that the materials or
equipment identified are necessarily the best available for the purpose
mentioned.

This publication was prepared by United States Government employees as
part of their official duties and is, therefore, a work of the U.S.
Government and not subject to copyright.