PURPOSE: To test an address bus and a data bus in a short time by comparing data on the address bus and data on the data bus at the time of write to a storage circuit.

CONSTITUTION: This system is provided with a storage circuit 11 having an address bus 12 and a data bus 13, a comparison circuit 14 which compares data on the address bus 12 and data on the data bus 13, a result report signal line 15 which reports the comparison result, and a comparison range designating signal line 16 which designates the comparison range of data on the address bus 12 and the data bus 13. In this constitution, a specific fault detection pattern is written, and the result report signal line is checked to confirm the normalcy of the address bus and the data bus.