4 Capturing trace after an event, and stopping

A minimum amount of time must elapse before a trace capture can be stopped.

The elapsed time between the trigger and the stopping of the trace must be long enough to allow the trace data to progress through the system. Any historical information, relating to previous events, must have been emitted.

The following figure shows a possible time-line of events where an event of interest, referred to as a trigger event, causes some trace to be captured. When the trace has been captured, the trace capture device can be stopped.

Figure 4-15 Capturing trace after an event and stopping
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When one trace source is used, there is no need to flush the system. Instead, the length of the trigger counter delay can be increased to enable more trace to be generated, effectively pushing out historical information.

The trigger event at time t1 is signaled to the TPIU through the cross-triggering system. The trace source that generated the trigger event might also embed some trigger information in its trace stream at this point.

The TPA only registers a trigger at time t3, when it is safe to stop trace capture. If the TPIU is in bypass or normal mode, it embeds a trigger in the formatted trace stream at time t3, and signals a trigger on tracectl.

In the figure, the action that causes trace capture to be stopped at time t3 can be one of the following:

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