PURPOSE: To reduce the manhour and to improve the working efficiency when an operation is confirmed and a trouble area is specified in an evaluation or a fault examination state by tracing surely only the specific one of those firmware executing operations or extracting a path that was actually executed out of those presumed firmware executing paths.

CONSTITUTION: An optional trace start address value of firmware is stored in a register 2, and the trace capacity to be traced is stored in a counter 3. The executing address of the firmware is traced through a memory access control part 5 and outputted. The value of the outputted address value is compared with the trace start address value by a comparator 6. The comparator 6 starts the counting operation of the counter 3 after detecting the coincidence between both address values. At the same time, the counter 3 outputs a write instruction signal 11 to the memory storing the trace data. Then the output of the signal 11 is stopped when the clock count value of the counter 3 reaches the value of the stored trace capacity.