PURPOSE: To increase the accuracy of a watch dog timer setting time by operating a counter with the output pulse of an initial voltage alarm (IVA) detecting circuit as a reference clock signal, and detecting abnormality based on the operating state of a selected counter when a firmware output is not inputted in a prescribed period.

CONSTITUTION: The counter is operated by plural counters 1 and deciding means 2 with an output pulse *D of the IVA detecting circuit as the reference clock signal. When a firmware output *A is not inputted in the prescribed period, the abnormality of a watch dog timer circuit is detected based on the operating state of the selected counter. Thus by paying attention to the utilization of the pulse for the prescribed period generated from the IVA detecting circuit and digitizing the pulse, an unstable element as a time setting circuit is eliminated, and the watch dog timer circuit which can correctly set a time can be obtained.