Keypad logic interface circuit

Details Keypad logic interface circuit Keypad logic interface circuit

1980-11-30

1982-11-02

Popek, Joseph A.

H04M 150

Patent

active

043574963

ABSTRACT:
A keypad logic interface circuit (200) provides a switch closure output signal representative of a selected one of a plurality of digits on a crosspoint contact array keypad (100). The selected one of the plurality of digits provides the switch closure signal by diverting a source current (225) from a first to a second direction. The circuit encodes each one of four column outputs from the keypad into a two-bit code. An output signal from two or more columns at the same time causes the circuit to produce an inhibit output signal reflecting a multiple button-push condition. The circuit also encodes each of four row outputs from the keypad into a two-bit code and produces an inhibit output signal when multiple row output signals are received.

REFERENCES:
patent: 4196318 (1980-04-01), Nelson
American Microsystems, Inc., S2559 Digital Tone Generator, Jun. 1977, pp. 1-12.

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