Microcomputer keyboard input circuitry

Details Microcomputer keyboard input circuitry Microcomputer keyboard input circuitry

1978-02-24

1980-09-09

Caldwell, Sr., John W.

Communications: electrical

Audible indication

Percussion-type sound producer

364200, G06F 302

Patent

active

042220386

ABSTRACT:
Keyboard input circuitry for use in a microcomputer continuously scans a keyboard having a plurality of keys organized into K columns and J rows. A counter under control of a reset signal and clock signal, sequentially provides K output signals for enabling the K column conductors. When a key in the Kth column and Jth row is depressed, the Kth output signal from the counter will be coupled to the Jth row. Thus, the logical state of the J row conductors will determine whether or not a key of the enabled column of keys is depressed or not. The microcomputer includes a register, a memory, and a peripheral interface adapter circuit. The microcomputer provides the reset signal and clock signal to the register and to the counter by way of the peripheral interface adapter circuit, for maintaining synchronism between the register and counter. For each enabled column of keys, the microcomputer senses the logical states of the J row conductors via the peripheral interface adapter circuit, and then ascertains whether or not a particular key is depressed by the sensed logical state of its row conductor and the state of the register.

REFERENCES:
patent: 3483553 (1969-12-01), Blankenbaker
patent: 3750113 (1973-07-01), Cencel
patent: 3921166 (1975-11-01), Volpe
patent: 3949365 (1976-04-01), Kashio
patent: 3955460 (1976-05-01), Southard
patent: 3973256 (1976-08-01), Stoesser et al.
patent: 3979730 (1976-09-01), Bennett et al.
patent: 4020391 (1977-04-01), Baxter
patent: 4020467 (1977-04-01), Hashimoto et al.
patent: 4030079 (1977-06-01), Bennett et al.
patent: 4106011 (1978-08-01), Melanson et al.

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