User guide

Instrumentation Trace Macrocell Unit

ID072410 Non-Confidential

9.2 ITM functional description

The ITM generates trace information as packets. Multiple sources can generate packets. If

multiple sources generate packets at the same time, the ITM arbitrates the order in which

packets are output. These 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 Cortex-M3 clock or the bitclock rate of the Serial

Wire Viewer (SWV) output clocks the counter.