5.2.4. Exception occurs immediately after trace turn-on

Whenever the PTM turns on tracing, it generates an I-sync packet. The address of this packet is the target address of the last waypoint. The following subsections describe the PTM trace generated when an exception occurs before the processor reaches a waypoint instruction:

Exception occurs before execution of instruction at the I-sync target address

If an exception occurs before the processor has executed any instructions after the last waypoint target address, the PTM outputs an exception branch address packet immediately after the I-sync packet that indicates trace turn-on. This means the trace output is:

  1. The I-sync packet indicating trace turn-on. The address is the target of the last waypoint, for example 0x1000.

  2. An exception branch address packet, indicating the exception type and vector address.

This trace indicates that the exception occurred before the processor executed any instructions at the target address of the I-sync packet, 0x1000 in the example.

Exception occurs after execution of instruction at the I-sync target address

If an exception occurs after the processor has executed one or more instructions after the last waypoint, but before it reaches a new waypoint instruction, the PTM upgrades the last instruction executed to a waypoint instruction, and then traces the exception branch. This means the trace output is:

  1. The I-sync packet indicating trace turn-on. The address is the target of the last waypoint, for example 0x1000.

  2. A waypoint update packet indicating the last instruction executed, for example 0x1050.

  3. An exception branch address packet, indicating the exception type and vector address.

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