Coded data generation or conversion – Bodily actuated code generator – Including keyboard or keypad
Patent
1996-07-08
1997-10-14
Hofsass, Jeffery
Coded data generation or conversion
Bodily actuated code generator
Including keyboard or keypad
341 22, 341 24, 345168, 345174, 364707, 36470912, H03K 1794, H03M 1100
Patent
active
056776870
ABSTRACT:
The present invention is directed to a system and methodology where virtually no DC power dissipation is used during keyboard scanning or key closure. This is done by replacing the passive pull-up (or pull down) resistors of previous schemes by input/output (I/O) circuits with repeaters and utilizing a scanning protocol and methodology which take advantage of the bidirectional I/O devices with repeaters. In a preferred embodiment, a plurality of CMOS bidirectional I/O circuits with repeaters are used, one for each row and column line in a switch matrix. A low power, switch activation scanner circuit determines activation of a switch. The circuit is coupled to or may include a plurality of switches, arranged in rows and columns, each row output line intersecting each column output line at a different node, for coupling a first row to a first column at a first node when a first switch of the plurality of switches is activated. A plurality of bidirectional input/output devices is arranged as two sets arranged in a matrix fashion. A first set of the two sets is comprised of a plurality of rows and a second set of the two sets comprising a plurality of columns. Each input/output device is comprised of an input to the input/output device, an output coupled to an output line, an output control for controlling the output of the input/output device such that a predetermined control signal coupled to the output control enables a signal coupled to the input to pass through to the output or places the output in a high impedance state, and a repeater circuit, coupled to the output of the input/output device, for holding the most current signal level at the output when the I/O device output is in a high impedance state.
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IBM Technical Disclosure Bulletin, "Key Coding Arrangement" by F. Buffard, vol. 21, No. 11, Apr. 1979.
Edwards, Jr. Timothy
Hofsass Jeffery
VLSI Technology Inc.
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