221CHAPTER 2 DEPENDENCE FUNCTIONS2.4.5 Real-time TraceWhile execution a program, the address, data and status information, and the datasampled by an external probe can be sampled in machine cycle units and stored in thetrace buffer. This function is called real-time trace.In-depth analysis of a program execution history can be performed using the datarecorded by real-time trace.■ Trace BufferThe data recorded by sampling in machine cycle units, is called a frame.The trace buffer can store 64K frames (65536). Since the trace buffer has a ring structure, when it becomesfull, it automatically returns to the start to overwrite existing data.■ Trace DataData sampled by the trace function is called trace data.The following data is sampled:• Address• Data• Status Information- Access status: Read/Write/Internal access, etc.- Device status: Instruction execution, Reset, Hold, etc.- Queue status: Count of remaining bytes of instruction queue, etc.- Data valid cycle information: Data valid/invalid(Since the data signal is shared with other signals, it does not always output data. Therefore, the tracesamples information indicating whether or not the data is valid.)■ Data Not TracedThe following data does not leave access data in the trace buffer.- Portion of access data while in native mode.When operating in the native mode, the F2 MC-16L/16LX family of chips sometime performssimultaneous multiple bus operations internally. However, in this emulator, monitoring of the internalROM bus takes precedence. Therefore, other bus data being accessed simultaneously may not be sampled(in the debugging mode, all operations are sampled).■ Frame NumberA number is assigned to each frame of sampled trace data. This number is called a frame number.The frame number is used to specify the display start position of the trace buffer. The value 0 is assigned totrace data at the triggering position for sequencer termination. Negative values are assigned to trace data thathave been sampled before arrival at the triggering position (See Figure 2.4-1).If there is no triggering position for sequencer termination, the value 0 is assigned to the last-sampled tracedata.
