In the ARM core such as cortex-R4, it has ETM and Debug so I want ask What's the difference between ETM and Debug?
Try this:
ARM Information Center
HTH, Pete
Thanks very much for your answer!
And I find the answer here:
http://www.arm.com/zh/products/system-ip/debug-trace/trace-macrocells-etm/
When it comes to debug or to optimize an embedded system, embedded developers have two main options available to them: