JPS5784369A - Abnormality detecting system for circuit device - Google Patents

Abstract

PURPOSE:To make it possible to detect the abnormality of a device, by making such an arrangement that rectangular wave signals are put out at a constant cycle when the device is operating normally, and, when the signals are at the levels of 0 and 1, counting and resetting are performed by respectively different counters. CONSTITUTION:When a circuit device 21 is in a normal condition, 2-position control signals are issued from CPU, etc., that is, rectangular wave signals b1 of a constant cycle 2T2 are continuously put out at equal intervals in conditions of 0 and 1. In first counter circuit 22a, counting is conducted when the output b1 of the device 21 is 1, the counter is reset when the output is 0, and pulses of a built-in constant-cycle pulse oscillator are counted when the counter is in operation. On the other hand, second counter circuit 22b operates conversely to the counter 22a. It is possible, by doing so, to allow counting of either counter to reach above a given value, b2 or b3 of an abnormal signal to be put out to outside and an abnormal signal b4 to be put out through an OR circuit 23, even at the time of occurrence of such an abnormality that a signal b1 keeps holding 0 or 1.