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Restoring Keyboard Indicator State After Disconnect

IP.com Disclosure Number: IPCOM000035996D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28

Publishing Venue

IBM

Related People

Authors:
Trinh, HC [+details]

Abstract

This article describes a personal computer keyboard interrupt handler to detect the presence of basic assurance test (BAT) code generated each time the keyboard is plugged in. Indicator bits O, 1 and 2 are set to O, causing a mismatch to indicator bits 4, 5 and 6, forcing the keyboard interrupt handler to set the keyboard indicator according to the bit value in indicator bits 4, 5 and 6, thereby restoring the previous state.