Patent Publication Number: US-7911216-B2

Title: Semiconductor integrated circuit, debug/trace circuit and semiconductor integrated circuit operation observing method

Description:
This application is the National Phase of PCT/JP2008/051078, filed Jan. 25, 2008, which claims priority based on Japanese Patent Application 2007-033340 filed on Feb. 14, 2007, and should incorporate all the disclosure thereof herein. 
     TECHNICAL FIELD 
     The present invention relates to operation tracing in a semiconductor integrated circuit. 
     BACKGROUND ART 
     With the recent increased complexity of built-in devices, establishment of a technique for performing efficient debugging at the stage of development has been demanded. For debugging most built-in devices, a method of setting up a break point using an incircuit emulator (ICE), a method of executing steps, and others have been used. However, there are many cases in which these methods cannot be used because it is impossible to adapt the operation timing with the timing of the surrounding circuit when the system is required to have real-time properties. 
     Under such circumstances, an importance of the observation of the status change and the behavior by tracing the operation inside the device has being increased. 
     On the other hand, in order to reduce production cost of built-in devices, there are often the cases where they do not have much margin as to internal memory capacity and CPU performance. Therefore, the method of storing an operation log by software processing, which is used by usual computer equipment typified by servers and personal computers, cannot be satisfactorily used by a built-in device. Further, in built-in devices, a customized system LSI is often used, so that it is often important to make observation on the behavior of the bus, the behavior of the peripheral circuits and the like, which cannot be observed by software processing alone. 
     For this reason, usually a technique for extracting signals for checking the operational status of a system LSI through monitoring terminals is provided, and it is an effective method is to store the change of the operational status as traced data by using the monitoring terminals and to analyze it. A technology using this technique is disclosed in Japanese Patent Application Laid-open 2002-24201 (which will be referred to hereinbelow as “Document 1”). 
       FIG. 1  is a block diagram showing an internal configuration of a system LSI described in Document 1. The system LSI in  FIG. 1  includes MPU core (control circuit)  91 , built-in RAM (Random Access Memory, storage circuit)  92  that stores the program for operating MPU core  91 , peripheral circuit  93  for performing transmission and reception of signals with MPU core  91 . The system LSI is also connected to system LSI peripheral apparatus  5 , so that the two transmit and receive signals to and from each other. Built-in RAM  92  also incorporates a debug supporting function program in addition to other than the program for operating MPU core  91 . 
     Further, debug supporting circuit  914  incorporating signal selection circuit  931  is provided inside MPU core  91 . Peripheral circuit  93  incorporates signal selection circuit  932 . In addition, signal selection circuit  933  for selecting a final monitor signal is provided. The selecting operation of each of signal selection circuits  931  to  933  is controlled by monitor signal control circuit  4 . 
     The system LSI in Document 1 includes signal selection circuit  931  for selecting any one of the internal signals in MPU core  91 , signal selection circuit  932  for selecting any one of the internal signals in peripheral circuit  93  and signal selection circuit  933  for selecting either one of the outputs from these signal selection circuits  931  and  932 , and the system LSI can arbitrarily switch the selecting operation of each of signal selection circuits  931  to  933  as required. Accordingly, it is possible to analyze in detail the internal operation of the system LSI in real-time. Further, even if the monitoring terminals are limited, it is possible to easily switch and output a plurality of monitoring signals. 
     DISCLOSURE OF INVENTION 
     However, the tracing system disclosed in Document 1 has some problems. 
     The tracing system disclosed in Document 1 operates on the premise that trace data is output to the outside of the LSI, so that the amount of observable trace data per unit time is limited by the speed of the communication line to the outside, the built-in buffer capacity and the like. Accordingly, there occurs a case in which a desired operation cannot be checked in a system or the like that internal operation speed is high. 
     Further, since, in the tracing system disclosed in Document 1, the signals to be observed are limited to those selected so as to reduce the amount of trace data, it is impossible to make a decision in a particular condition based on behaviors of all the signals to be observed. 
     One object of the present invention is to provide a means for enabling observation of a desired operation while observing arbitrary signals to be observed, without being affected by the speed of the connected communication line and by the built-in buffer capacity. 
     In order to attain the above object, a semiconductor integrated circuit according to one embodiment mode of the present invention is a semiconductor integrated circuit having a debugging function, and includes: 
     a main functional structure that executes continuous predet ermined operations to continuously generate events associated with said operations; and 
     a debug/trace circuit, which stores beforehand a control information list including a plurality of entries in a sequential manner so as to identify an event which needs an observation based on a series of events, each entry consisting of a set of detection condition indicating information to detect generation of a target event and operation indicating information to designate an operation in accordance with the result of comparison between said detection condition indicating information and the event occurring at said main functional structure, and which continuously performs in accordance with said control information list, comparison of an event occurring at said main functional structure with the detection condition indicating information of one entry in said control information list, and execution of the operation designated by said operation indicating information paired with said detection condition indicating information in accordance with the result of said comparison, to identify said event. 
     A debug/trace circuit of the present invention is a debug/trace circuit built in a semiconductor integrated circuit including a main functional structure that executes continuous predetermined operations to continuously generate events associated with said operations, and includes: 
     a control information list holder which stores beforehand a control information list including a plurality of entries in a sequential manner so as to identify an event needing observation based on a series of events, each entry consisting of a set of detection condition indicating information to detect generation of a target event and operation indicating information to designate an operation in accordance with the result of comparison between said detection condition indicating information and the event occurring at said main functional structure; 
     an event detector which continuously performs in accordance with said control information list, comparison of an event occurring at said main functional structure with the detection condition indicating information of one entry in said control information list; and, 
     a controller which, in accordance with the result of said comparison from said event detector, executes the operation designated by said operation indicating information that is paired with said detection condition indicating information. 
     An operation observing method for a semiconductor integrated circuit of the present invention is an operation observing method for a semiconductor integrated circuit to observe the operation of a main functional structure by a debug/trace circuit built in a semiconductor integrated circuit including a main functional structure that executes continuous predetermined operations to continuously generate events associated with said operations, and includes the steps of: 
     storing beforehand a control information list including a plurality of entries in a sequential manner so as to identify an event needing observation based on a series of events, each entry consisting of a set of detection condition indicating information to detect generation of a target event and operation indicating information to designate an operation in accordance with the result of comparison between said detection condition indicating information and the event occurring at said main functional structure; and, 
     continuously performing in accordance with said control information list, comparison of an event occurring at said main functional structure with the detection condition indicating information of one entry in said control information list, and execution of the operation designated by said operation indicating information that is paired with said detection condition indicating information in accordance with the result of said comparison, to identify and observe said event. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       [ FIG. 1 ] is a block diagram showing the configuration of a tracing system disclosed in Document 1. 
       [ FIG. 2 ] is a block diagram showing a configuration of the first exemplary embodiment. 
       [ FIG. 3 ] is a structural diagram showing a control information list in the first exemplary embodiment. 
       [ FIG. 4 ] is a flow chart showing a processing flow of a debug/trace system in the first exemplary embodiment. 
       [ FIG. 5 ] is a block diagram showing a configuration of the second exemplary embodiment. 
       [ FIG. 6 ] is a structural diagram showing a control information list in the second exemplary embodiment. 
       [ FIG. 7 ] is a flow chart showing a processing flow of a debug/trace system in the second exemplary embodiment. 
       [ FIG. 8 ] is a block diagram showing a configuration of the third exemplary embodiment. 
       [ FIG. 9 ] is a structural diagram showing a control information list in the third exemplary embodiment. 
       [ FIG. 10 ] is a flow chart showing a processing flow of a debug/trace system in the third exemplary embodiment. 
       [ FIG. 11 ] is a block diagram showing a specific configuration of a controller and an event detector used in common in the first and second examples. 
       [ FIG. 12 ] is a flow chart showing a processing flow of a debug/trace system in the first example. 
       [ FIG. 13 ] is a structural diagram showing a control information list in the first example. 
       [ FIG. 14 ] is a flow chart showing a processing flow of a debug/trace system in the second example. 
       [ FIG. 15 ] is a structural diagram showing a control information list in the second example. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     The exemplary embodiments of the present invention will be described in detail with reference to the drawings. 
     First Exemplary Embodiment 
       FIG. 2  is a block diagram showing an overall configuration of a debug/trace system according to the first exemplary embodiment of the present invention. Referring to  FIG. 2 , system LSI  1  includes main functional structure  2  and debug/trace circuit  3 . The system LSIs mentioned herein may include configurations having a plurality of chips integrated therein, such as SiP (System in Package), MCP (Multi Chip Module), PoP (Package on Package) and the like. It is also assumed that the system LSI has a typical configuration in which the capacity of communication inside the system LSI is high enough compared to the capacity of communication to the outside of the LSI. Main functional structure  2  is a circuit for realizing essential desired functions of system LSI  1 , and is made up of MPU core  21  and peripheral circuit  22  as a typical example. Debug/trace circuit  3  includes event detector  31 , controller  32  and control information list holder  33 . Control information list holder  33  holds control information list  4 . 
       FIG. 3  is a structural diagram showing a control information list in the first exemplary embodiment. Details of control information list  4  stored in control information list holder  33  will be described using  FIG. 3 . 
     Control information list  4  is a list having a plurality of entries  41  arranged therein, each entry  41  being composed of detection condition indicator  42  and operation indicator  43 . Detection condition indicator  42  describes the condition for detecting an event to be observed. It is possible to detect an event (target event) that meets the detection condition by comparing an occurring event with the detection condition. Operation indicator  43  describes the operation of controller  32  when a target event has been detected. Examples of the described operation of controller  32  include indication as to data output, indication as to change of the entry to be next referred to, indication to end the measurement, indication to output data to the outside of the LSI (which will hereinbelow be referred to as simply “the outside”), indication to output control information to the outside, and the like. 
       FIG. 4  is a flow chart showing a processing flow of a debug/trace system in the first exemplary embodiment. The operation of the debug/trace system of the present exemplary embodiment will be described based on the flow chart in  FIG. 4 . 
     To begin with, when controller  32  receives an observation start command from the outside, controller  32  initializes the entry readout position from control information list  4  held in controller  32  itself (Step S 1 ). At this time, a value of the top entry in control information list  4  is usually designated, but another value may be designated depending on use. 
     Thereafter, controller  32  reads out one entry  41  from control information list  4  held in control information list holder  33  and holds the value therein (Step S 2 ). Then, controller  32  sets up detection condition for event detector  31  in accordance with detection condition indicator  42  of the retrieved entry  41  (Step S 3 ). 
     Thereafter, event detector  31  continues comparing events with the set detection condition, and gives an event detection notice to controller  32  when detecting an event that meets the condition for notifying event occurrence (Step S 4 ). The condition for notifying event occurrence is the condition which indicates whether or not occurrence of an event is notified to controller  32 . For example, a notice of occurrence of an event may be given only when the event meets the detection condition or a notice of occurrence of an event may be given in either case where the event meets or does not meet the detection condition. Also, event detector  31  holds detailed information on events therein. 
     Thereafter, controller  32  refers to operation indicator  43  of entry  41  (Step S 5 ) and performs control operations in accordance with an indication of operation indicator  43  (Step S 6 ). Examples of the control operation include reading detailed information of an event from event detector  31  to output it as event data, outputting user data written in control information list  4 , outputting control information, typified by error notice and normal end notice, and others. 
     Controller  32  further determines whether or not an end command is included in the indication from operation indicator  43  of entry  41  (Step S 7 ). If an end command is included in the indication, controller  32  ends the measurement. If no end command is included in the indication, controller  32  changes the entry readout position as required (Step S 8 ), and returns to read out a next entry  41 . 
     Description herein was given in the form of executing the operation one step at a time for description simplicity, but a plurality of steps may be executed at the same time or may be executed in an assembly-line manner based on a pipeline-like method, in order to achieve a high-speed operation. 
     According to the exemplary embodiment, since control information list  4  including a plurality of entries  41  corresponding to a series of operations that need to be checked has been prepared in advance and since the event detection condition and control are changed one to another in accordance with control information list  4 , it is possible to internally check based on many signal variations that particular events have occurred in a particular order and record the trace data. As a result, it becomes possible to trace the event sequences inside the system LSI, hence it is possible to check desired operations while observing arbitrary signals of a high-speed observation target without being affected by the speed of the communication line and by the built-in buffer capacity. 
     Second Exemplary Embodiment 
     Next, the second exemplary embodiment of the present invention will be described in detail with reference to the drawings. 
       FIG. 5  is a block diagram showing an overall configuration of the second exemplary embodiment of the present invention. In the system LSI of the present exemplary embodiment, main functional structure  21  is composed of operational units such as MPU core  21 , DSP, accelerators and the like, each executing a predetermined series of operations. Further, the system LSI of the present exemplary embodiment includes operational unit controller  34  in debug/trace circuit  3 , in addition to the first exemplary embodiment shown in  FIG. 2 . Operational unit controller  34  transmits signals for controlling the operational units in main functional structure  2 . 
       FIG. 6  is a structural diagram showing a control information list in the second exemplary embodiment. As shown in the control information list structural diagram of  FIG. 6 , operational unit control indicator  431  exists inside operation indicator  43  of control information list  4 . Information written in operational unit control indicator  431  is information on which operational unit inside main functional structure  2  an indication is given to, what kind of a control indication is given or no indication is given, for operational unit controller  34 . Examples of control indication include stop command, start command, etc. 
       FIG. 7  is a flow chart showing a process flow of a debug/trace system in the second exemplary embodiment. The operation of the debug/trace system of the second exemplary embodiment will be described based on the flow chart in  FIG. 7 . 
     To begin with, when controller  32  receives an observation start command from the outside, controller  32  initializes the entry readout position from a control information list held in itself (Step S 11 ). At this time, the top event in the control information list is usually designated, but another value may be designated depending on use. 
     Thereafter, controller  32  reads out one entry  41  from control information list  4  held in control information list holder  33  and holds the value therein (Step S 12 ). Then, controller  32  sets up a detection condition for event detector  31  in accordance with detection condition indicator  42  of the retrieved entry  41  (Step S 13 ). 
     Thereafter, event detector  31  continues comparing events with the set detection condition and gives an event detection notice to controller  32  when an event meets the condition for notifying event occurrence (Step S 14 ). The condition for notifying event occurrence is the condition on which whether or not the occurrence of an event is notified to controller  32 . For example, a notice of occurrence of an event may be given only when the event meets the detection condition or a notice of occurrence of an event may be given in both cases where the event meets and does not meet the detection condition. Event detector  31  also holds detailed information on events therein. 
     Thereafter, controller  32 , referring to operation indicator  43  of entry  41  (Step S 15 ), determines whether or not any control command to an operational unit exits (Step S 16 ). If there is any control command to an operational unit, controller  32  transmits the operational unit control command to operational unit controller  34 . Operational unit controller  34 , in accordance with the indication of the received operational unit control command, performs a control operation to the operational unit inside main functional structure  2  (Step S 17 ). Examples of control on an operational unit include suspension, activation, status check and the like of the operational unit. 
     When no control command to an operational unit existed at the determination of Step S 16 , or after the control operation at Step S 17 , controller  32  performs other control operations in accordance with the indication of operation indicator  43  of entry  41  (Step S 18 ). Examples of other control operations include reading detailed information of an event from event detector  31  to output the data, outputting user data written in control information list  4 , performing control output, typified by error notice and normal end notice, and others. 
     Controller  32  further determines whether or not an end command is included in the indication from operation indicator  43  of entry  41  (Step S 19 ). If an end command is included in the indication, controller  32  ends the measurement. If no end command is included in the indication, controller  32  changes the entry readout position as required (Step S 20 ), and returns to readout of next entry. 
     Herein, for description simplicity, the operation was described by executing one step at a time, but a plurality of steps may be executed at the same time or may be executed in an assembly-line manner based on a pipeline-like method, in order to achieve a high-speed operation. 
     In debugging, there is a case in which the status such as memory content and the like at the moment a certain event has occurred during program execution needs to be checked. However, if operational units were operating, there is a possibility that the value of the memory content at the location which needs be checked has changed when it is checked after the operation has been ended. Also, if an observation is performed simply based on occurrence of an event, the event which needs to be observed will be included, so that there are cases where it is important to exclude events other than the target. 
     To deal with this, the present exemplary embodiment, in addition to the function of tracing event sequences similarly to the first exemplary embodiment, further includes operational unit controller  34 , and operational unit control indicator  431  in control information list  4  is introduced to use control information list  4  that includes a control command to a particular operational unit suited to the event to be checked. As a result, it is possible to control the operational unit in a manner convenient for observation. For example, it is possible to stop a certain operational unit immediately after occurrence of a target event. Hence, it is possible to check the memory content immediately after occurrence of a certain event and acquire the data associated with the operational unit. 
     Third Exemplary Embodiment 
       FIG. 8  is a block diagram showing an overall configuration of the third exemplary embodiment of the present invention. Referring to  FIG. 8 , the system LSI of the present exemplary embodiment includes performance measuring portion  35  in addition to the first exemplary embodiment shown in  FIG. 2 . Performance measuring portion  35  measures performance such the frequency of occurrence of events, the amount of bus traffic, the delay values and the like, in accordance with the input command information. 
       FIG. 9  is a structural diagram showing a control information list in the third exemplary embodiment. As shown in the control information list structural diagram of  FIG. 9 , performance measurement control indicator  432  exists inside operation indicator  43  of control information list  4 . Written in performance measurement control indicator  432  is command information to performance measuring portion  35  to control performance measurement. Examples of command information include a command for setting up a parameter that indicates what kind of performance measurement is performed and a command for starting or ending the performance measurement. 
       FIG. 10  is a flow chart showing a process flow of a debug/trace system in the third exemplary embodiment. The operation of the debug/trace system of the third exemplary embodiment will be described based on the flow chart in  FIG. 10 . 
     To begin with, when controller  32  receives an observation start command from the outside, controller  32  initializes the entry readout position from a control information list held in itself (Step S 21 ). At this time, the top entry in the control information list is usually designated, but another value may be designated depending on use. 
     Thereafter, controller  32  reads out one entry  41  from control information list  4  held in control information list holder  33  and holds the value therein (Step S 22 ). Then, controller  32  sets up detection condition for event detector  31  in accordance with detection condition indicator  42  of retrieved entry  41  (Step S 23 ). 
     Thereafter, event detector  31  continues comparing events with the set detection condition and gives an event detection notice to controller  32  when an event meets the condition for notifying event occurrence (Step S 24 ). The condition for notifying event occurrence is the condition on which whether or not occurrence of an event is notified to controller  32 . For example, a notice of occurrence of an event may be given only when the event meets the detection condition or a notice of occurrence of an event may be given in both cases where the event meets and does not meet the detection condition. Event detector  31  also holds detailed information on events. 
     Thereafter, controller  32 , referring to operation indicator  43  of entry  41  (Step S 25 ), determines whether or not there is any command information on performance measurement (Step S 26 ). 
     If there is any command information as to performance measurement, controller  32  transmits the command information as to performance measurement to performance measuring portion  35 . Performance measuring portion  35 , in accordance with the command information received from controller  32 , controls performance measurement (Step S 27 ). Examples of performance measurement control include setup of measurement targets and measurement items, starting and ending of measurement, and the like. 
     When there is no control command as to performance measurement existed at the determination of Step S 26 , or after the control operation at Step S 27 , controller  32  performs other control operations in accordance with the content of indication of operation indicator  43  of entry  41  (Step S 28 ). Examples of other control operations include reading detailed information of an event from event detector  31  to output the data, outputting user data written in control information list  4 , performing control output, typified by error notice and normal end notice, and others. 
     Controller  32  further determines whether or not an end command is included in the indication from operation indicator  43  of entry  41  (Step S 29 ). If an end command is included in the content of indication, controller  32  ends the measurement. If no end command is included in the indication, controller  32  changes the entry readout position as required (Step S 30 ), and returns to readout of the next entry. 
     Description herein was given in the form of executing the operation one step at a time for description simplicity, but a plurality of steps may be executed at the same time or may be executed in an assembly-line manner based on a pipeline-like method, in order to achieve a high-speed operation. 
     In debugging a program or tuning its performance, there is a case in which measurement targets and measurement items are need to be changed depending on the occurrence of a certain event during program execution. There is also a case where measurement needs to be started or ended depending on an occurrence of a certain event. If an observation is performed simply based on an occurrence of an event, there is a case in which data that is not needed to be measured is measured. In such a case, it is important to remove such events other than those to be measured. 
     To deal with this, the present exemplary embodiment, in addition to the function of tracing event sequences similarly to the first exemplary embodiment, further includes performance measuring portion  35 , and performance measurement control indicator  432  is introduced in control information list  4  to use control information list  4  that includes a control command as to performance measurement suited to the event to be checked. As a result, it is possible to control the measurement operation in accordance with the event. For example, it is possible to start or end measurement immediately after occurrence of a target event. It is also possible to change the measurement target and the content of measurement immediately after occurrence of an event to be the target. 
     First Example 
     Next, specific examples of the above exemplary embodiments will be described. 
       FIG. 11  is a block diagram showing a specific configuration of event detector  31  and controller  32 . Referring to  FIG. 11 , event detector  31  is composed of detection condition holder  311 , condition determinater  312  and event holder  313 . 
     Detection condition holder  311  holds condition for detecting events. Condition determinater  312  observes the signals from main functional structure  2  to controller  32  to determine whether or not each event meets the detection condition held at detection condition holder  311 . When an event meets the detection condition, condition determinater  312  sends an event detection notice to controller  32 . Event holder  313  holds the details of the event detected by condition determinater  312 . 
     With this arrangement, event detector  31  holds the detection condition set from controller  32  in detection condition holder  311 , detects occurrence of an event at condition determinater  312  if an event that matches the detection condition occurs, and holds the details of the event at event holder  313 . 
     On the other hand, controller  32  is composed of control executor  321 , entry readout position holder  322  and entry information holder  323 . 
     Control executor  321  performs control in accordance with control information list  4  and gives operation indications to each portion in association with it. Entry readout position holder  322  holds the position of control information entry  4  to be read out next from control information list holder  33 . Entry information holder  323  holds the information of entry  4  read out from control information list holder  33 . 
     With this configuration, controller  32  reads out entry  4  designated by the positional information held at entry readout position holder  322 , from control information list holder  33 , holds it in entry information holder  323  and performs control in accordance with entry  4  held at entry information holder  323 . 
       FIG. 12  is a flow chart showing a process flow of a debug/trace system in the first example.  FIG. 13  is a structural diagram showing a control information list in the first example. 
     The operation in this example will be described based on  FIGS. 12 and 13 . 
     Here, Step S 32  to Step S 34  in  FIG. 12  correspond to Step S 2  in  FIG. 4 . Step S 35  to Step S 36  correspond to Step S 3  in  FIG. 4 . Further, Step S 37  to Step S 40  correspond to Step S 4  in  FIG. 4 . 
     In the example of control information list  4  in  FIG. 13 , operation indicator  43  incorporates hit control indicator  433 , hit output indicator  434 , mishit control indicator  438  and mishit output indicator  439 . 
     Hit control indicator  433  is an operation indication for specifying the operation inside debug/trace circuit  3  when an event meeting the detection condition was detected (at the time of hit). Hit output indicator  434  is information for designating whether or not event data at the time of hit is output. 
     Mishit control indicator  438  is an operation indication for specifying the operation when an event other than the detection condition was detected (at the time of mishit). Mishit output indicator  439  is information for designating whether or not event data at the time of mishit is output. 
     Herein, as a simple example, one hit control indicator  433  and one hit output indicator  434  are shown. However, the present invention should not be limited to this. As another example, it is possible to construct entries  41  such that a plurality of detection conditions can be set in detection condition indicator  42  and a plurality of hit control indicators  433  and hit output indicators  434  can be set in operation indicator  43 . With this construction, it is possible to set up entries  41  so as to perform a different process depending on the content of the detected event. 
     Referring to  FIG. 12 , at first, when an observation start command is input to controller  32  from the outside, control executor  321  sets the initial value into entry readout position holder  322  (Step S 31 ). When entry readout position holder  322  is set with the initial value, the position from which an entry is read out from control information list  4  is initialized. At this time, the top in control information list  4  is usually designated, but another value may be designated depending on use. 
     Thereafter, controller  32  gives notice of the readout position from entry readout position holder  322  to control information list holder  33  (Step S 32 ). Control information list holder  33  outputs entry  41  corresponding to the notified readout position (Step S 33 ). Controller  32  stores entry  41  output from control information list holder  33  into entry information holder  323  located inside (Step S 34 ). 
     Next, control executor  321  refers to detection condition indicator  42  of entry  41  stored in entry information holder  323  (Step S 35 ) and writes the detection condition indicated therein into detection condition holder  311  of event detector  31  (Step S 36 ). 
     Thereafter, when a change in the signal from main functional structure  2  occurs (Step S 37 ), condition determinater  312  in event detector  31  determines whether or not the change meets the condition for notifying an event, based on the observation result of the signal and the detection condition held at detection condition holder  311  (Step S 38 ). If any occurrence of an event that meets the notice condition is not detected when the notice condition is confirmed, condition determinater  312 , returning to Step S 37 , repeats the same process until an event that meets the notice condition occurs. On the other hand, when occurrence of an event that meets the notice condition is detected when the notice condition is confirmed, condition determinater  312  transmits an event detection notice to controller  32  (Step S 39 ). 
     As receiving an event detection notice (Step S 40 ), control executor  321  determines whether it is a hit notice or a mishit notice (Step S 41 ). A hit notice is information which, when the notice condition includes information that the detection condition is satisfied, gives notice that the notice condition (detection condition) was satisfied. A mishit notice is information which, when the notice condition includes information that the detection condition is not satisfied, gives notice that the notice condition was satisfied (that is, detection condition was not satisfied). 
     If a hit notice is given, control executor  321 , acquires the content of the control to be performed by referring to hit control indicator  433  of entry  41  stored in entry information holder  323 , and acquires the information as to whether or not event data needs to be output by referring to hit output indicator  434  (Step S 42 ). On the other hand, if a mishit notice is given, control executor  321 , acquires the content of the control to be performed by referring to mishit control indicator  438  of entry  41  stored in entry information holder  323 , and acquires the information as to whether or not event data needs to be output by referring to mishit output indicator  439  (Step S 43 ). 
     Subsequently, control executor  321  determines whether or not event data needs to be output, based on the information acquired at Step S 42  or Step S 43  (Step S 44 ). If event data needs to be output, control executor  321  reads out the detailed information on the stored events from event holder  313  of event detector  31  and outputs the necessary information as event data (Step S 45 ). 
     When it was determined at Step S 44  that event data does not need to be output, or when event data was output at Step S 45 , control executor  321  executes control in accordance with the control content acquired at Step S 42  or Step S 43  (Step S 46 ). The control content has been given in hit control indicator  433  or in mishit control indicator  438 . 
     When the indication is “no change”, control executor  321  returns to Step S 32  without doing anything. If the indication is “to the next”, control executor  321  rewrites the value in entry readout position holder  322  to the value that represents the position of the next entry (Step S 47 ), and returns to Step S 32 . If the indication is “end”, control executor  321  outputs an end notice to the outside (Step S 48 ) and ends the measurement. 
     Description herein was given in the form of executing the operation one step at a time for description simplicity, but a plurality of steps may be executed at the same time or may be executed in an assembly-line manner based on a pipeline-like method, in order to achieve a high-speed operation. 
     Here, the operation shown in  FIG. 12  becomes different partly in the steps to be executed, depending on how the operation of event detector  31  is defined. 
     For example, if event detector  31  is specified to operate such as to send an event detection notice at Step S 39  only when the observed result has satisfied the detection condition at Step S 38 , no transition from Step S 41  to Step S 43  will occur on the control executor  321  side. 
     On the other hand, if, for example, event detector  31  is specified to operate such as to send an event detection notice when the observed result has satisfied the detection condition or not at Step S 38 , event detector  31  will never perform a repeating operation on the “No” route to return to Step S 37 . 
     Alternatively, when the hit notice condition and mishit notice condition are defined separately while event detector  31  is specified to send an event detection notice to controller  32  when either of these is satisfied, there is a chance that both event detector  31  and controller  32  will execute all the steps shown in  FIG. 12 . 
     Further, even when, with a notice condition defined, event detector  31  is specified to send an event detection notice to controller  32  when the notice condition is satisfied and to define the scope for hit notice within the notice condition, there is a chance that both event detector  31  and controller  32  will execute all the steps shown in  FIG. 12 . 
     Next, the observing method in this example will be described taking a specific example of control information list  4  shown in  FIG. 13 . Here, an example in which the fact that the signal from main functional structure  2  has agreed with the set value as a detection condition is handled as the event that satisfies the detection condition will be illustrated. This corresponds to an access-associated event. For example, there are cases where a particular access to a bus, memory, or a register of a peripheral circuit is regarded as an event that meets the detection condition. In access-related events, an access to a particular address, an access having data of a particular value, an access from a particular operational unit, and others are able to be set as the event to be detected. As another example, there are cases where the value of a timer, counter or register having taken a predetermined value is regarded as an event that meets the detection condition. 
     One particular value may be set as the detection condition, but another method also may be applicable. As another example, there is a method in which a range is set with an upper limit and a lower limit. There is also another conceivable method in which a particular set value of a plurality of bits is designated and a mask value is used so as to determine whether each bit of the set value is made valid or invalid when compared to the observation signal. There is another conceivable method in which a bit map is used to determine whether comparison is made valid or invalid for every accessor. Further, the above-described plural methods may be used in combination. 
     Referring to  FIG. 13 , control information list  4  includes three entries  411 ,  412  and  413 . 
     Detection condition indicator  42  of entry  411  is set with “bus access to address A”. Accordingly, if there is a bus access to address A, it is detected as an event of entry  411 . Similarly, detection condition indicator  42  of entry  412  is set with “bus access to address B”. Detection condition indicator  42  of entry  413  is set with “bus access to address C”. 
     Hit control indicators  433  of entry  411  and entry  412  are set with “to the next”. “To the next” indicates going forward to monitor the next entry. Accordingly, when, for instance, an event of entry  411  is hit, the control goes to monitor the next entry  412 . Similarly, when an event of entry  412  is hit, the control goes to monitor the next entry  413 . 
     Hit control indicator  433  of entry  413  is set with “end”. “End” indicates that the measurement is completed at that point. Accordingly, if an event of entry  413  is hit, the measurement is ended at that point. 
     Hit output indicators  434  of entries  411  to  413  are set with “output”. “Output” indicates outputting of event data. Accordingly, when, for instance, an event of entry  411  is hit, the event data at that time is output. Similarly, when an event of entry  412  is hit, the event data at that time is output. When an event of entry  413  is hit, the event data at that time is output. 
     Mishit control indicator  438  of entries  411 ,  412  and  413  are set with “no change” while mishit output indicator  439  are set with “no output”. “No change” indicates continuation of monitoring the same entry without changing the entry. “No output” indicates non-outputting of event data. Accordingly, when, for instance, no event of entry  411  is hit, monitoring the event of entry  411  is continued as is while no event data will be output. Similarly, when no event of entry  412  is hit, monitoring the event of entry  412 ′ is continued as is while no event data will be output. When no event of entry  413  is hit, monitoring the event of entry  413  is continued as is while no event data will be output. 
     When measurement is started using the control information list  4  set as above, entry  411  is designated as the initial value of the entry to be referred to first. When the signal from main functional structure  2  is one other than bus access to address A, the state of waiting for a bus access to address A to be observed continues without changing the entry to be referred to as the monitoring target and without outputting event data. 
     If a bus access to address A occurs, an event of entry  411  is detected. As a result, the entry to be referred to is changed to entry  412 , and the data value at the access to address A is output as the event data. 
     Similarly, in the observation referring to entry  412 , the state of waiting for a bus access to address B to be observed continues. When it is observed, its event data is output and the operation goes to the observation referring to entry  413 . In the observation referring to entry  413 , when a bus access to address C is observed, the event data is output to end the measurement. 
     As above, use of control information list  4  thus set as in  FIG. 13  makes it possible to acquire the event data (e.g. data value) of each bus access as the trace data when bus accesses occurred in the order of addresses A, B and C, being mixed with various events during execution of a certain program. Since no unnecessary data will be acquired, the buffer capacity required for data recording can be markedly cut down. Further, since event detection and data recording can be done following control information list  4  without the need of successive operations from the outside of the system LSI, the operation will not be limited by the speed of the communication line to the outside. 
     Second Example 
     The specific configurations of event detector  31  and controller  32  of the second example are the same as those of the first example shown in  FIG. 11 . 
       FIG. 14  is a flow chart showing a process flow of a debug/trace system in the second example.  FIG. 15  is a structural diagram showing a control information list in the second example. 
     The operation in this example will be described based on  FIGS. 14 and 15 . 
     Here, Step S 52  to Step S 54  in  FIG. 14  correspond to Step S 2  in  FIG. 4 . Step S 55  to Step S 56  correspond to Step S 3  in  FIG. 4 . Further, Step S 57  to Step S 60  correspond to Step S 4  in  FIG. 4 . 
     In the example of control information list  4  shown in  FIG. 15 , similarly to the example in  FIG. 13 , operation indicator  43  incorporates hit control indicator  433 , hit output indicator  434 , mishit control indicator  438  and mishit output indicator  439 . 
     Hit control indicator  433  is an operation indication for specifying the operation inside debug/trace circuit  3  when an event meeting the detection condition was detected (at the time of hit). Hit output indicator  434  is information for designating whether or not event data at the time of hit is output. 
     Mishit control indicator  438  is an operation indication for specifying the operation when an event other than the detection condition is detected (at the time of mishit). Mishit output indicator  439  is information for designating whether or not event data at the time of mishit is output. 
     Herein, as a simple example, one hit control indicator  433  and one hit output indicator  434  are shown. However, the present invention should not be limited to this. As another example, it is possible to construct entries  41  such that a plurality of detection conditions can be set in detection condition indicator  42  and a plurality of hit control indicators  433  and hit output indicators  434  can be set in operation indicator  43 . With this construction, it is possible to set up entries  41  so as to perform a different process depending on the content of the detected event. 
     Referring to  FIG. 14 , at first, when an observation start command is input to controller  32  from the outside, control executor  321  sets the initial value into entry readout position holder  322  (Step S 51 ). When entry readout position holder  322  is set with the initial value, the position from which an entry is read out from control information list  4  is initialized. At this time, the top in control information list  4  is usually designated, but another value may be designated depending on use. 
     Thereafter, controller  32  gives notice of the readout position from entry readout position holder  322  to control information list holder  33  (Step S 52 ). Control information list holder  33  outputs entry  41  corresponding to the notified readout position (Step S 53 ). Controller  32  stores entry  41  output from control information list holder  33  into entry information holder  323  located inside (Step S 54 ). 
     Next, control executor  321  refers to detection condition indicator  42  of entry  41  stored in entry information holder  323  (Step S 55 ) and writes the detection condition indicated therein into detection condition holder  311  of event detector  31  (Step S 56 ). 
     Thereafter, when a change in the signal from main functional structure  2  occurs (Step S 57 ), condition determinater  312  in event detector  31  determines whether or not the change meets the condition for notifying an event, based on the observation result of the signal and the detection condition held at detection condition holder  311  (Step S 58 ). If any occurrence of an event that meets the notice condition is not detected when the notice condition is confirmed, condition determinater  312 , returning to Step S 57 , repeats the same process until an event that meets the notice condition occurs. On the other hand, when occurrence of an event that meets the notice condition is detected when the notice condition is confirmed, condition determinater  312  transmits an event detection notice to controller  32  (Step S 59 ). 
     As receiving an event detection notice (Step S 60 ), control executor  321  determines whether it is a hit notice or a mishit notice (Step S 61 ). A hit notice is information which, when the notice condition includes information that the detection condition is satisfied, gives notice that the notice condition (detection condition) was satisfied. A mishit notice is information which, when the notice condition includes information that the detection condition is not satisfied, gives notice that the notice condition was satisfied (that is, detection condition was not satisfied). 
     If a hit notice is given, control executor  321 , acquires the content of the control to be performed by referring to hit control indicator  433  of entry  41  stored in entry information holder  323 , and acquires the information as to whether or not event data needs to be output by referring to hit output indicator  434  (Step S 62 ). On the other hand, if a mishit notice is given, control executor  321 , acquires the content of the control to be performed by referring to mishit control indicator  438  of entry  41  stored in entry information holder  323 , and acquires the information as to whether or not event data needs to be output by referring to mishit output indicator  439  (Step S 63 ). 
     Subsequently, control executor  321  determines whether or not event data needs to be output, based on the information acquired at Step S 42  or Step S 63  (Step S 64 ). If event data needs to be output, control executor  321  reads out the detailed information on the stored events from event holder  313  of event detector  31  and outputs the necessary information as event data (Step S 65 ). 
     When it was determined at Step S 64  that event data does not need to be output, or when event data was output at Step S 65 , control executor  321  executes control in accordance with the control content acquired at Step S 62  or Step S 63  (Step S 66 ). The control content has been given in hit control indicator  433  or in mishit control indicator  438 . 
     When the indication is “no change”, control executor  321  returns to Step S 52  without doing anything. If the content of indication is “to the next”, control executor  321  rewrites the value in entry readout position holder  322  to the value that represents the position of the next entry (Step S 67 ), and returns to Step S 52 . If the content of indication is “move”, control executor  321  rewrites the value in entry readout position holder  322  to the value that represents the designated entry readout position, and returns to Step S 52 . If the content of indication is “end”, control executor  321  outputs an end notice to the outside (Step S 69 ) and ends the measurement. If the content of indication is “error”, control executor  321  outputs an error notice to the outside (Step S 70 ) and ends the measurement. 
     Description herein was given in the form of executing the operation one step at a time for description simplicity, but a plurality of steps may be executed at the same time or may be executed in an assembly-line manner based on a pipeline-like method, in order to achieve a high-speed operation. 
     Next, the observing method in this example will be described taking a specific example of control information list  4  shown in  FIG. 15 . Here, an example in which a change of a particular signal from main functional structure  2  is handled as the event that satisfies the detection condition will be illustrated. For example, there are cases where the fact that a cut-in signal or control signal becomes valid or invalid is regarded as an event that meets the detection condition. There is also a case where the fact that a certain operational unit changes in state is regarded as an event. 
     Though the event detection condition may be set for one particular signal as a detection condition, another method also may be applicable. As another example, there is a conceivable method in which the values of detection conditions for a plurality of events are designated, and a bit map is used to set whether these are made valid or invalid for each event. This arrangement makes it possible to designate a particular event group. 
     Referring to  FIG. 15 , control information list  4  includes three entries  414 ,  415 ,  416  and  417 . 
     Detection condition indicator  42  of entry  414  is set with “event A”. Accordingly, if event address A occurs, it is detected as an event of entry  414 . Similarly, detection condition indicator  42  of entry  415  is set with “event B”. Detection condition indicator  42  of entry  416  is set with “event C”. Detection condition indicator  42  of entry  417  is set with “event D”. 
     Hit control indicators  433  of entry  414 , entry  415  and entry  416  are set with “to the next”. “To the next” indicates going forward to monitor the next entry. Accordingly, when, for instance, an event of entry  414  is hit, the control goes to monitor the next entry  415 . Similarly, when an event of entry  415  is hit, the control goes to monitor the next entry  416 . When an event of entry  416  is hit, the control goes to monitor the next entry  417 . 
     Hit control indicator  433  of entry  417  is set with “end”. “End” indicates that the measurement is completed at that point. Accordingly, if an event of entry  417  is hit, the measurement is ended at that point. 
     Hit output indicators  434  of entries  414  to  417  and mishit output indicator  439  of entries  415  to  417  are set with “output”. “Output” indicates outputting of event data. Accordingly, when, for instance, an event of entry  414  is hit, the event data at that time is output. Similarly, when an event of entry  415 ,  416  or  417  is hit, the event data at that time is output. When an event of entry  415 ,  416  or  417  is mishit, the event data at that time is output. 
     Mishit control indicators  438  of entries  414  and  417  are set with “no change”. “No change” indicates continuation of monitoring the same entry without changing the entry. Accordingly, when no event of entry  414  or  417  is hit, monitoring the event of entry  414  is continued as is. 
     Mishit output indicator  439  of entry  414  is set with “no output”. “No output” indicates non-outputting of event data. Accordingly, when no event of entry  414  is hit, no event data will be output. 
     Mishit control indicator  438  of entry  415  is set with “error”. “Error” indicates giving an error notice to the outside and ending the measurement at that point. Accordingly, when an event of entry  415  is mishit, an error notice is output and the measurement is ended at that point. 
     Mishit control indicator  438  of entry  416  is set with “move to  414 ”. “Move” indicates going forward to monitor a designated entry. In this case, “ 414 ” is designated as the destination. Accordingly, when an event of entry  416  is mishit, the control goes to monitor entry  414 . 
     When measurement is started using control information list  4  set as above, entry  414  is designated as the initial value of the entry to be referred to first. Hereby, monitoring of event A is started. If the detected event is other than event A, the entry to be referred to as the monitoring target is not changed and no event data is output, and the state of waiting for event A to be observed continues. When event A occurs, an event of entry  414  is detected. As a result, the entry to be referred to is changed to entry  415 , and event data is output. The event data is information associated with the detected event, for example. 
     When a next event is observed after event A has been observed, the content of entry  415  is referred to. In entry  415 , an error notice is output when an event other than event B was detected, and the event data is output to end the measurement. When the measurement was terminated due to error, it is possible to check what happened by examining the event data. 
     On the other hand, when event B was observed, the entry to be referred to is changed to entry  416  and event data is output. When a next event is detected after event B has been observed, the content of entry  416  is referred to. In entry  416 , the operation returns to entry  414  so that monitoring of event A is started when an event other than event C is detected. Though the fact that an event is other than event C is not an error, because it is not the trace condition either, the operation is started once again from monitoring of event A. 
     When event C was detected, then the content of entry  417  is referred to. In entry  417 , when an event other than event D is detected, the event data is output but the entry to be referred to will not be changed. As a result, the event data of all the events will be recorded as trace data until event D is detected. When event D is detected, an end notice is output to terminate the measurement at that point. 
     As above, use of the control information list  4  thus set as in  FIG. 15  makes it possible to start tracing of events when events A, B and C have occurred in succession during execution of a certain program and terminate the trace when event D occurs. 
     Having described the present invention referring to the exemplary embodiments and examples, the present invention should not be limited to the above exemplary embodiments and examples. Various changes that can be understood to those skilled in the art can be made in the configuration and detail of the present invention defined in claims, within the scope of the present invention.