PURPOSE:To easily obtain trace information by the slight increase of hardware by using the area of a memory where an ECC is stored as the trace control area of a firmware program at the time of a debug. CONSTITUTION:In a normal action state, ECC codes corresponding to the respective instructions of a program memory 1 are written into an ECC memory 2, the ECC code is read out and an ECC check is executed at the time of executing the firmware program. At this time, a trace control circuit 3 does not function. In the debug action state of the firmware program, the ECC memory 2 is used for setting trace codes. At this time, the ECC check action is stopped and an instruction read out of the program memory 1 is executed without the guarantee of the ECC check. In the debug action state of the above- mentioned program, the trace control circuit 3 is made to function and a writing into a trace memory 4 is executed with the significance of the trace code as identification.
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