EM357-RTR datasheet(204/241 Pages) SILABS

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13. Instrumentation Trace Macrocell (ITM)

The EM35x integrates the standard ARM® Instrumentation Trace Macrocell (ITM). The ITM is an application-driven

trace source that supports printf style debugging to trace software events and emits diagnostic system information

from the ARM® Data Watchpoint and Trace (DWT). Software using the ITM generates Software Instrumentation

Trace (SWIT). In addition, the ITM provides coarse-grained timestamp functionality. The ITM emits trace

information as packets, and these packets are sent to the Trace Port Interface Unit (TPIU). Three sources can

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

packets are output. The three sources, in decreasing order of priority, are:



Software trace. Software can write directly to ITM stimulus registers, emitting packets.



Hardware trace. The DWT generates packets that the ITM emits.



Time stamping. Timestamps are emitted relative to packets, and the ITM contains a 21-bit counter to

generate the timestamps.

The Ember software utilizes the ITM for efficiently generating debug data. Altering the ITM configuration may

conflict with Ember debug output.

For further information on the ITM, contact Silicon Labs support for the ARM® CortexTM-M3 Technical Reference

Manual, the ARM® CoreSight™ Components Technical Reference Manual, the ARM® v7-M Architecture

Reference Manual, and the ARM® v7-M Architecture Application Level Reference Manual.

EM357-RTR Datenblatt(PDF) 204 Page - Silicon Laboratories