What is the supported ETM trace port size on the RT1021? The 1020 reference manual suggests that TRACEDATA can be 1, 2, or 4 bits and 4-bit mode is recommended (see 220.127.116.11 CoreSight trace port interface). However, this seems to conflict with the actual behavior of the device. With a debug connection to the 1021 evaluation kit. I observed that the ARM TPIU Supported Port Size register is fixed to 1 (0xE0040000=0x00000001). If my understanding is correct, this register indicates that only PORT_SIZE=1 is supported by the device and this cannot be changed. My evaluation kit has been modified to support ETM trace and I was able to verify that 1-bit ETM trace is working, but not 2-bit or 4-bit mode.
We are evaluating the 1021 as a possible migration from the K24. With the k24 we are using 4-bit TRACEDATA mode and this seems to meet our needs. On the k24 I confirmed that the Supported Port size register indicates 4-bit mode is supported. ETM trace is important for our applications so I am concerned with the apparent limit of 1-bit ETM Trace and at this point it is unclear whether this will cause some kind of trace data bottleneck.