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8.5. TPIU triggers

Currently the only usage of triggers is by the trace capture device. This method is straightforward when using one trace source. When using multiple trace sources there can be a time disparity between the trace sources that generate a trigger and when the trigger packet appears at the output of the trace port. See the CoreSight Architecture Specification for more information on triggers.

A trigger can be interpreted as an event that occurred. This can be:

  • Directly from an event such as a pin toggle from the CTI.

  • A delayed event such as a pin toggle that has been delayed coming through the Trigger Counter Register.

  • The completion of a flush.

Table 8.4 extends the ETMv3 specification on how a trigger is represented

Table 8.4. CoreSight representation of triggers
TRACECTLTRACEDATATriggerCaptureDescription
[1][0]Yes/NoYes/No
0xxNoYesNormal trace data
100YesYesTrigger packet[a]
110YesNoTrigger
1x1NoNoTrace disable

[a] The trigger packet encoding is required for the current ETMv3 protocol that uses a special encoding for triggers that always occur on the lower bits of TRACEDATA.