6 bit keyboard encoder

ously. When a key is depressed, the output of IC2 remains logic zero until the counter reaches the corresponding address for that particular key. At that moment, the high (IC1) input level is passed the six latches on to the output of IC2 so that N2 and (IC4 and IC5) receive a clock pulse via gatewsillthen N3. The address of the depresse appear on the output lines DO ... D5. At the same time, transistor Ti is turned on making the output of N1 go high to provide a keyboard strobe pulse. encoder This keyboard encoder is constructed entirely from ordinary, easily obtainable, CMOS ICs. The heart of the circuit consists of two multiPlexer/demulti- L. Witkam 6 bit keyboard plexer ICs (IC1 and IC2). The first of the 4015s, IC1, functions as the multiplexer, its input being nnected to the positive supply voltage via resistor When the key is released, the output of Ni will - remain high for the period of time taken for capaci tor C2 to discharge via resistor R3. The oscillator frequency ca...