JPS57196361A - Fault detecting device of microcomputer - Google Patents

Abstract

PURPOSE:To detect a fault even in case when the fault has occurred in a clock generating circuit or a counter, by providing a fault detecting function for backup, in a computer. CONSTITUTION:A clock signal CK of a clock generating circuit 2 is inputted in advance to a microcomputer 1, and when the computer 1 receives the clock signal, it executes its inherent processing as the computer 1 over the subsequent time T1. In the course of its processing, the computer 1 executes a write operation of a prescribed value M to an internal memory, and after that, over a time T2, a value of the internal memory is counted down by an internal clock pulse. When the signal CK is inputted before said value becomes a prescribed value ''0'', the inherent processing of the computer is executed again. On the other hand, in case when the value of the internal memory has become ''0'' in a state that the signal CK is not inputted, it is considered to be occurrence of a fault, and a countermeasure for the fault is executed.