Keyboard circuit

Details Keyboard circuit Keyboard circuit

1975-10-24

1978-08-08

Caldwell, Sr., John W.

Communications: electrical

Audible indication

Percussion-type sound producer

340365S, G08C 2500

Patent

active

041060113

ABSTRACT:
A simplified keyboard for a terminal device, calculator, or the like, in which each key is sequentially scanned and parallel key code data is sent to an entry register. A pair of flip-flops in combination with firmware ascertain that only valid key code data is sent to the entry register for utilization by the system, providing double entry and key bounce protection. The firmware further provides N-key rollover and auto repeat with a variable repeat rate, and expands the keyboard from a single-mode to an eight-mode capability.

REFERENCES:
patent: 3448254 (1969-06-01), Verhoeff
patent: 3675239 (1972-07-01), Ackerman et al.
patent: 3790881 (1974-02-01), Smith
patent: 3792466 (1974-02-01), Arnold et al.
patent: 3803592 (1974-04-01), Hatley
patent: 3825926 (1974-07-01), Brownback
patent: 3828258 (1974-08-01), Hills
patent: 3886543 (1975-05-01), Marin
patent: 3949365 (1976-04-01), Kashio
patent: 3973256 (1976-08-01), Stoesser et al.

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