SWITCH OPERATION DETECTING CIRCUIT, MICROPROCESSOR WITH OPERATION SWITCH IDENTIFYING FUNCTION INCORPORATED THEREIN CORRESPONDING TO SAME CIRCUIT, AND MICROCOMPUTER SYSTEM MADE UP BY COMBINING THEM TOGETHER

摘要

PROBLEM TO BE SOLVED: To provide a switch operation detecting circuit allowing a practically sufficient number of switches to be used even in the event that an electric apparatus is designed assuming the use of a low-priced microprocessor having a small number of input ports. SOLUTION: This switch operation detecting circuit is equipped with a plurality of switch connection terminals T0 to be respectively connected to a plurality of switches or objects of operation detection, a plurality of CR differentiating circuits one-to-one corresponding to the plurality of switch connecting terminals T0 each having a specific time constant and outputting differential pulses of waveforms determined by the specific time constants in response to the operation of the switches connected to the switch connection terminals T0, and one common output terminal Tout of for outputting the differential pulses of the plurality of CR differentiating circuits. In response to the operation of one of the switches connected to the plurality of switch connection terminals T0, a differential pulse having a time-constant curve specific to the switch operated is sent out from the output terminal Tout.