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| Home > Introduction > About the Program Trace Macrocell > Trace compression | |||
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| Home > Introduction > About the Program Trace Macrocell > Trace compression | |||
The trace produced by the PTM is compressed to reduce the number of additional pins required on the ASIC, or to reduce the amount of memory required by the ETB.
The trace is compressed using the following techniques:
the PTM outputs address information only when the processor branches to a location that cannot be directly inferred from the source code
when the PTM outputs an address, it does not output any high-order bytes that have not changed since the previous trace address
the PTM outputs trace only when it can use the full width of the trace output interface.
For the debugger to be able to decode the trace, you must supply a static image of the code being executed. Self-modifying code cannot be traced because of this restriction.
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