12.2. ITM functional description

The ITM generates trace information as packets. There are four sources that can generate packets. If multiple sources generate packets at the same time, the ITM arbitrates the order that packets are output. The four sources in decreasing order of priority are:

Software trace

Software can write directly to ITM stimulus registers to generate packets.

Hardware trace

The DWT generates these packets, and the ITM outputs them.

Time stamping

Timestamps are generated relative to packets. The ITM contains a 21-bit counter to generate the timestamp. The processor clock output clocks the counter.

Global system timestamping

Timestamps can optionally be generated using a system-wide 64-bit count value. The same count value is used for inserting timestamps in the ETM trace stream, permitting coarse-grain correlation.

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