3.17.3. PTM behavior when the OS Lock is set

You set the OS Lock by writing the lock key of 0xC5ACCE55 to the ETMOSLAR. See OS Lock Access Register, ETMOSLAR. When the OS Lock is set all PTM functions are disabled. This means that:

You must use the WFI mechanism to ensure that the FIFO is empty before you remove power from the macrocell.


The WFI mechanism must be present on any processor and PTM combination that provides power-down support. See the Technical Reference Manual (TRM) for your processor and PTM macrocell for more information.

When the OS Lock is cleared, you can restart tracing. The counters, sequencer, start/stop block and Instrumentation resources continue operating from their held state. If the implementation maintains the sticky state of the address range comparators during OS Lock then the address range comparators continue operating with this held sticky state. However, if the PTM has been powered down since the OS Lock was set:

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