JPS6455627A - Microcomputer reset circuit - Google Patents

Abstract

PURPOSE:To return a device to the initial state by detecting momentary power failure by a power failure detecting circuit to output an interrupt signal and inputting this interrupt signal through a delay circuit to certainly output a reset signal from a gate circuit at the time of the momentary power failure. CONSTITUTION:A voltage stabilized power supply circuit 10 which supplies power to a logic circuit having a microcomputer, a reset circuit 11 which outputs a signal in accordance with the output potential of this circuit 10, a power failure detecting circuit 14 which is connected to the interrupt input of the microcomputer and outputs an interrupt signal to the interrupt input of the microcomputer when detecting the stop or the fall of power supplied to the voltage stabilized power supply circuit 10, a delay circuit 15 which delays the output of the power failure detecting circuit 14, and a gate circuit 16 which has the output connected to the reset input of the microcomputer or the like and outputs the reset signal in accordance with the output signal of the delay circuit 15 or the output signal of the reset circuit 1 are provided. Thus, a microcomputer reset circuit is obtained which outputs the reset signal even at the time of a momentary power failure.