ETB

The Embedded Trace Buffer (ETB) is a small, circular on-chip memory space where trace information is stored during capture. It contains the data that is normally exported via trace pins immediately after it has been captured by the ETM. The buffer can be read via a regular debug interface device, once capture has been completed.

No additional special trace port is required, meaning that the ETB can be read via a normal J-Link. The trace functionality through J-Link is limited by the size of the ETB. When capturing runs, the trace information in the buffer will be overwritten every time the buffer size has been reached. The result of the limited buffer size is that no more data can be traced than the buffer can hold. Because of this limitation, an ETB is not a true alternative to direct access to an ETM via J-Trace.