12.5.4. Turning off the PTM

During normal operation, the PTM buffers individual bytes of trace, and only generates output when at least 4 bytes are available. To enable the clocks to be gated, the PTM provides a mechanism to flush all trace out of the FIFOs in certain conditions. This differs from the AFVALID mechanism, which only ensures that trace up to a certain point has been output.

When the PTM requires to enter an idle state, all trace in the FIFO is output. After the final data on the ATB interface has been accepted, the PTM is in an idle state.

If the Programming bit is set, trace generation is stopped. The PTM then enters the idle state. This ensures that no trace packets remain. After the PTM completes the idle state transition with the Programming bit set, reading the Status Register reports the Programming bit as set. The Programming bit must not be cleared until the Status Register reports the Programming bit as set.

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