SELF-DIAGNOSING SYSTEM OF MICROCOMPUTER

摘要

PURPOSE:To improve the response of a self-diagnosis and to make a decision on a fault possible, by allowing a watchdog timer pulse to reset a time counting circuit which determines the period of output pulses of a pulse generating circuit. CONSTITUTION:A pulse train PA is inputted to one of external interruption terminals of the microcomputer 1, i.e. iNT1 and a two-input OR circuit 4. The watchdog timer pulse output terminal WDP of the microcomputer 1 is connected to the reset terminal RST of a M-stage shift register 2. The output of the pulse generating circuit 3 which generates a pulse train PB with a specific period TW is inputted to the other external interruption terminal iNT2 of the microcomputer 1 and said OR circuit 4. Consequently, the output of OR between the pulse strings PA and PB is supplied to the clock terminal (CLK) of the shift register 2.