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Chapter 5: Plugging into a Target System
Configuring the Emulator for In-Circuit Operation
Note
In a case like this where there was no trigger, the emulator does not know which
line in the trace to begin disassembly on. In this example you would need to issue
the command:
display trace disassemble_from_line_number -14 <RETURN>
in order to get the display shown above. Choosing the trace line number to begin
disassembly from is not always easy. You need to choose a line number which has
the fetch of the first word of an instruction. You may recognize symbols in your
trace, or specific opcode values. Note that when you are tracing high-level routines
such as a C routine, the emulator can use source-line information to help it choose
the proper location for disassembly.
This trace shows how valuable the time stamp can be, not just in highlighting
cycles that are unusually long, but also in showing the effect of reprogramming of
OR1. You can see how the program fetch on line -011 took approximately 600ns,
but the program fetch on line -009 took only 280ns. This is a result of the write to
OR1 on line -010 which changed the internal DTACK generation from 6 wait states
to 1 state.
Many users capture a trace that shows the processor halting, but fail to take the time
to analyze the information in the trace. Examining a trace carefully will often help
you find the exact cause of a problem.
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