6.4.5. Context ID packets

When the Context ID changes, a Context ID is output to give the new value. It comprises the following components:

The number of bytes output depends on the ProcIDSize field. bits [15:14] of the ETMCR, see Main Control Register, ETMCR. If Context ID tracing is disabled by setting these bits to b00, Context ID packets are never generated.

If the Context ID is changed by a data transfer that would normally have been traced, and a Context ID packet is output, it is implementation specific whether the Context ID packet is generated instead of or in addition to the normal data trace.

This means that, when Context ID tracing is enabled, data trace might be missing for an instruction that changes the Context ID.

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