KEY MATRIX USING ANALOGUE/DIGITAL CONVERTER

摘要

PURPOSE: A key matrix using an analogue/digital converter is provided to prevent a power waste by turning on a power by a play key only using two ports and simplify an additional algorithm for converting power on state into a power off state without using the play key. CONSTITUTION: A microcomputer(10) senses a plurality of key inputs through two ports(key1, key2). A drive IC(20) turns on/off a power according as a play key of a CD player is inputted. A resistor(R1) is connected to an operation power(VCC) which supplies the key 1 port of the microcomputer(10) and an analogue/digital converter type key matrix. The first diode(D1) is connected to a contact of the resistor(R1) and the key 1 port in a normal direction. A play key of the key matrix is connected between one side of the first diode(D1) and a ground. A resistor(R2) of the key matrix is connected to a contact of the key 1 port of the microcomputer(10) and the resistor(R1). Thus, a plurality of key matrix circuit are constituted. The second diode(D2) is connected between a contact of the first diode(D1) and the play key of the key matrix and a start port of the drive IC(20) in a normal direction.