J-Link / J-Trace User Guide (UM08001) - Microcontrollers

9.3 Embedded Trace Buffer (ETB)
The ETB is a small, circular on-chip memory area where trace information is stored
during capture. It contains the data which is normally exported immediately after it
has been captured from the ETM. The buffer can be read out through the JTAG port of
the device once capture has been completed. No additional special trace port is
required, so that the ETB can be read via J-Link. The trace functionality via J-Link is
limited by the size of the ETB. While 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 not more data can be traced than the
buffer can hold. Through this limitation is an ETB not in every case an fully-fledged
alternative to the direct access to an ETM via J-Trace.
J-Link / J-Trace (UM08001) © 2004-2010 SEGGER Microcontroller GmbH & Co. KG
193