CMSIS Debug Support

CMSIS provides for Cortex-M3 / Cortex-M4 debug support via the Instrumented Trace Macrocell (ITM).

The ITM unit contains 32 ITM channels. A write operation to an ITM channel memory location creates a trace record with:

• output value
• time stamp
• program location

CMSIS uses ITM channel 0 for printf-style debug information.

• A standard interface is used to transmit the debug information.
• ASCII values are written to ITM Stimulus Port 0.
• Zero CPU cycles are required to get the data out of the processor.
• The intrusive output routine adds to execution time and needs memory, but can be shipped within the end product.
• uVision outputs the transmitted data of ITM channel 0 to a debug console "Debug (printf) Viewer" window.

The use of the ITM Stimulus Ports is only possible if:

• Serial Wire Debug (SWD) Port is used
• Serial Wire Output (SWO) is enabled

This example shows the use of the CMSIS debug functions.