PURPOSE: To improve the time setting accuracy by starting a time count by a microcomputer when a start signal is fed to an input terminal, outputting a time-up signal to a 1st output terminal and producing a timer output corresponding to the signal from an output circuit.

CONSTITUTION: A microcomputer 1 starts count when a start signal Vin is fed to an input terminal 101 and outputs a time-up signal to a 1st output terminal 102. When the microcomputer is in normal operation according to a program and a crystal oscillation circuit 104 oscillates a clock signal of a prescribed frequency, a signal having a prescribed frequency appears at a 2nd output terminal 103. Moreover, at an abnormal operation, a frequency signal different from that in the normal operation appears at the 2nd output terminal 103. A monitor circuit 3 is connected of its input side to the 2nd output terminal 103 and inhibits production of a timer output when the circuit 3 receives an abnormal frequency signal from the 2nd output terminal 103.