INPUT CIRCUIT

PROBLEM TO BE SOLVED: To use a general purpose port in a microcomputer by a using method in proportion to an A/D port. SOLUTION: This input circuit connected to the general purpose port P for fetching the binary signals of a high voltage level signal and a low voltage level signal in the microcomputer is equipped with a comparator CMP for comparing a reference voltage corresponding to a power supply voltage +B with an input signal and outputting a compared result to the general purpose port P and an increase/decrease circuit for increasing/decreasing the reference voltage corresponding to the compared result of the comparator CMP.