Abstract: An apparatus and method for processing data is disclosed. The apparatus comprises a data processing circuit operable over a sequence of processing cycles to perform data processing operations in response to program instructions and a tracing circuit configurable to perform a selected one of a number of tracing activities in which corresponding trace data is generated indicative of operation of the data processing circuit in response to the program instructions. The tracing circuit is operable to be responsive to trace instructions inserted into the program instructions to control execution of the selected one of a number of tracing activities in order to generate the trace data, each trace instruction being operable to control execution of each of a number of the tracing activities. Hence, the tracing circuit is operable to perform a number of tracing activities and is configurable to perform a selected one of those tracing activities.

Abstract: Test access to an integrated circuit 2 is controlled by the use of test access enabling keys. A plurality of different test access enabling levels may be supported corresponding to different keys. The test access control may be performed by dedicated hardware or software executing a secure privilege mode.

Abstract: A microprocessor integrated circuit 104 is provided with a trace controller 120 that is responsive to trace initiating conditions to trigger commencement of tracing operation and generation of a trace data stream. In the case of a multi-word data transfer instruction LSM, the trace controller 120 is able to trigger tracing partway through that instruction such that a subset of the transfer specified by that instruction are included within the trace data stream. All transfers subsequent to the triggering transfer may be traced with those transfers subsequent to the triggering transfer being marked with place holder codes rather than more informative full trace data for the triggering transfer.

Abstract: A data processing system 2 is described having a central processing unit 4 and a diagnostic mechanism 10. The central processing unit 4 is switchable into a power-down mode from which it may resume into a normal operation mode. When the central processing unit 4 resumes into the normal operation mode, execution of program instructions is inhibited by the diagnostic mechanism 10 to allow the diagnostic mechanism to be appropriately programmed such that the immediate power-up code and operations can be properly diagnosed. The requirement to prevent program instruction execution on power-up is programmed by writing to a latch 16 within the diagnostic mechanism 10 prior to the power-down. The prevention of program execution may be achieved, for example, by generation of a halt request or by extending the time period for which the central processing unit 4 is held in reset following power-up.

Abstract: The present invention provides an asynchronous FIFO apparatus and method for passing data between a first clock domain and a second clock domain of a data processing apparatus, the first clock domain being asynchronous with respect to the second clock domain. The asynchronous FIFO apparatus comprises a main FIFO memory operable to store the data to be passed between the first and second clock domains, the main FIFO memory being accessible from each clock domain under the control of an access pointer associated with that clock domain. For one or both of the clock domains, the amount of data accessible per clock cycle is variable.

Abstract: A system-on-chip integrated circuit 2 is provided with multiple data processing circuits 4, 6, 8 each with an associated diagnostic interface circuit 16, 18, 20 connected via a diagnostic transaction bus 14 to a diagnostic transaction master circuit 12. The diagnostic master transaction circuit 12 issues diagnostic transaction requests to the diagnostic interface circuits 16, 18, 20. If the associated data processing circuits 4, 6, 8 are powered-down, or otherwise non responsive, then the diagnostic interface circuit 16, 18, 20 returns a diagnostic bus transaction error signal to the diagnostic transaction master circuit 12. A sticky-bit latch 30 within each diagnostic interface circuit 16, 18, 20 serves to record a power-down event and force generation of the diagnostic bus transaction error signal until that sticky bit is cleared by the diagnostic mechanisms.

Abstract: A data processing system 2 is described having a central processing unit 4 and a diagnostic mechanism 10. The central processing unit 4 is switchable into a power-down mode from which it may resume into a normal operation mode. When the central processing unit 4 resumes into the normal operation mode, execution of program instructions is inhibited by the diagnostic mechanism 10 to allow the diagnostic mechanism to be appropriately programmed such that the immediate power-up code and operations can be properly diagnosed. The requirement to prevent program instruction execution on power-up is programmed by writing to a latch 16 within the diagnostic mechanism 10 prior to the power-down. The prevention of program execution may be achieved, for example, by generation of a halt request or by extending the time period for which the central processing unit 4 is held in reset following power-up.

Abstract: A trace data system is provided in which flush request signals are generated and passed to trace data sources to trigger them to output any buffered trace data they are storing which was generated prior to the flush request being signalled. When the trace data has been flushed from these trace data sources, they signal this by generating a flush complete signal. The flushing of trace data may advantageously be performed prior to a power-down operation and using a trace bus bridge.

Abstract: Within a system-on-chip device 2 having multiple processing circuits 4, 6, 8, one processing circuit 4 may serve to perform diagnostic operations upon another processing circuit 8 by accessing diagnostic data relating to that other circuit. Thus, one processor may, for example, control and perform halting mode type diagnostic or code profiling upon another.

Abstract: A trace data formatter 30 assembles trace data frames 50. These trace data frames 50 include bytes which may either serve to carry a trace data source identifier ID or trace data. A system being traced has multiple trace data sources 12, 14, 16, 18 and when the trace data source which is generating the current trace data stream changes then a trace data source identifier ID is inserted within the trace data stream.

Abstract: An integrated circuit 2 is provided with multiple sources 12, 14, 16, 18 of trace data streams that are input via respective dedicated trace buses 20, 24 to a trace data stream combiner 22, 26. The trace data bus has trace data signal lines ATDATA for carrying trace data signals and trace source identifying signal lines ATID for carrying trace source identifying signals. A trace data stream replicator 28 may be used to replicate a single trace data stream such that the resulting multiple trace data streams may be subject to different post-replication processing/filtering as desired.

Abstract: An integrated circuit is provided with multiple data processing components associated with respective sources which generate trace data streams. A reference timestamp generator is provided and the trace data streams are annotated such that they are output off-chip together with reference timestamp data. Outputting the reference timestamp data together with the trace data streams enables temporal correlation between points in different trace data streams by trace analysis tools.

Abstract: A data processing apparatus controls cross-triggering of diagnostic processes on a plurality of processing devices. The data processing apparatus comprises a routing module having a plurality of broadcast channels, one or more of the broadcast channels being operable to indicate the occurrence of a diagnostic event on one or more of the plurality of processing devices. The data processing apparatus also comprises an mapping module associated with a corresponding processing device. The interface module programmably asserts diagnostic event signals from the associated processing device to one or more of the plurality of broadcast channels and programmably retrieves diagnostic events signals from processing devices other than the associated processing device from one or more of the plurality of broadcast channels. The retrieved diagnostic event data is used to facilitate triggering of a diagnostic process on the associated processing device in dependence upon said retrieved diagnostic event data.