Browse Prior Art Database

Keyboard Encoding Logic

IP.com Disclosure Number: IPCOM000092106D
Original Publication Date: 1968-Sep-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 87K

Publishing Venue

IBM

Related People

Igel, JJ: AUTHOR

Abstract

The outputs of single contact keyboard keys, not shown, are encoded into a six or eight-bit code. The keyboard is of the type having upper and lower shifts. Upper and lower shift signals are generated by logic circuitry 10 to provide proper encoding for each key. The upper and lower shift signals are applied to bit latches 1, 2, 4, 8, A, and B. These bit latches also receive inputs from Or's 15 which have their inputs connected to the keyboard contacts. Invalid character latch 20 is set if any key other than a numeric key is operated during the time a program control signal is available to restrict the upper shift to only numeric keys. When latch 20 is set, the Any Data key signal is inhibited and the keyboard data keys are locked out.

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Keyboard Encoding Logic

The outputs of single contact keyboard keys, not shown, are encoded into a six or eight-bit code. The keyboard is of the type having upper and lower shifts. Upper and lower shift signals are generated by logic circuitry 10 to provide proper encoding for each key. The upper and lower shift signals are applied to bit latches 1, 2, 4, 8, A, and B. These bit latches also receive inputs from Or's 15 which have their inputs connected to the keyboard contacts. Invalid character latch 20 is set if any key other than a numeric key is operated during the time a program control signal is available to restrict the upper shift to only numeric keys. When latch 20 is set, the Any Data key signal is inhibited and the keyboard data keys are locked out. The Any Data key signal is used to indicate that a data key is depressed and that the bit latches can be sampled. When a key is depressed, it is mechanically locked and remains locked until forward movement of a mechanical bail, not shown, takes place. When the bit latches are sampled, the keyboard is restored by the mechanical bail. When the bail is fully forward, the set of bail FWD contacts are made. The signal from these contacts is fed through delay 25 to reset latch 30. The resetting of latch 30 causes the bit latches to be reset.

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