RUN-AWAY DETECTOR FOR COMPUTER SYSTEM

PURPOSE:To detect the run-away when a CPU, etc., run away and to immediately introduce a system to a fail safe by directly monitoring an input signal of the CPU, etc., with a run-away detecting circuit provided at the external part of a run-away detecting object such as the CPU. CONSTITUTION:A microcomputer system has a CPU 1 of a microprocessor mode, a memory part 2 having a ROM to store fixed data, a RAM for storing data and the like, a peripheral control part 3, an address bus 4, a data bus 5 and a control bus 6 to communicate a reading signal and a writing signal and further, provides a CPU run-away detecting circuit 7 and links this to buses 4-6. This CPU run-away detecting circuit 7 monitors the set-up time and the holding time of respective input signals necessary to the normal action of the CPU 1, etc., and when the time cannot be maintained for a prescribed time, an abnormal signal is generated. Thus, the malfunction can be detected and the system can be immediately introduced to the fail safe.