METHOD AND DEVICE FOR DIAGNOSING HARDWARE

PROBLEM TO BE SOLVED: To automatically make a diagnosis without placing any load on a CPU by detecting abnormality occurring in an input device, an input/output controller, or various interfaces when there is no access. SOLUTION: A bus monitor device 4 monitors a control line connected to an I/O 3 by a control line monitor part 4a, and sets status information showing a state wherein there is no access on a system bus 2 for a specific time corresponding to a time-up time set previously in a timer 4c in a status register 4b and issues an interruption to the CPU 1 once detecting the said state. The CPU 1 once receiving the interruption from the bus monitor device 4 issues a diagnostic program to the I/O 3 to be diagnosed. This method does not load the CPU 1 with the detection of the no-access state and can make an efficient diagnosis by making good use of the time when there is no access.