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When the TPIU receives a trigger signal, it can request a flush of all trace components through the ATB slave interface.
This flush request depends on the settings in the Formatter and Flush Control Register. The flush request causes all information around the trigger event to be flushed from the system before normal trace information is resumed. The flush ensures that all information that is related to the trigger is output before the TPA, or other capture device, is stopped.
With FOnTrig set to 1, it is possible to indicate the trigger on completion of the flush routine. Knowing the trigger ensures that if the TPA stops the capture on a trigger, the TPA gets all historical data relating to the trigger.