Keyboard scanner apparatus and method

A digital keypad input device comprises a controller for driving a plurality of I/O signal lines selectively in input, output, and high impedance states. Each line operated in the output state presents an output logic signal that is detected, via a corresponding switch when closed, by another I/O li...

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Bibliographic Details
Main Authors FREEMAN; MARK S, MCELHINNEY; BRIAN S
Format Patent
LanguageEnglish
Published 06.03.1990
Subjects
BASIC ELECTRIC ELEMENTS
BASIC ELECTRONIC CIRCUITRY
CALCULATING
CODE CONVERSION IN GENERAL
CODING
COMPUTING
COUNTING
DECODING
ELECTRIC DIGITAL DATA PROCESSING
ELECTRIC SWITCHES
ELECTRICITY
EMERGENCY PROTECTIVE DEVICES
PHYSICS
RELAYS
SELECTORS
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Summary:A digital keypad input device comprises a controller for driving a plurality of I/O signal lines selectively in input, output, and high impedance states. Each line operated in the output state presents an output logic signal that is detected, via a corresponding switch when closed, by another I/O line operated in the input state. Other lines are operated in the high impedance state. The method of the invention enables the number of manual switches to exceed the number of I/O lines.
Bibliography:Application Number: US19880177078