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When programming the ETM registers, you must enable all the changes at the same time. For example, if the counter is reprogrammed, it might start to count based on incorrect events, before the trigger condition has been correctly set up.
You program and read the ETM registers using the Debug APB interface. This provides a direct method of programming the Cortex®‑R8 processor ETM.
You must use the ETM main enable in the TRCPRGCTLR to disable all trace operations during programming. in the following figure shows the procedure to follow.
The Cortex‑R8 processor does not have to be in the debug state while you program the ETM registers.