It is not possible to stop the program execution on a CPU register read or write, since this is not supported by any processor on-chip debug implementations. It is only possible to set breakpoints on program execution or memory accesses (read/write).
It is however possible to set a program or read/write breakpoint on a memory address with the condition that a CPU register has a specific value, e.g.:
Break.Set myFunc /Program /CONDition Register(R0)==0
TRACE32 will stop here the program execution every time the function myFunc is executed and will check the condition "Register(R0)==0". If the condition is false, the program execution will be resumed.