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Keyboard Controller

IP.com Disclosure Number: IPCOM000043380D
Original Publication Date: 1984-Aug-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Dean, M: AUTHOR [+2]

Abstract

In an IBM Personal Computer compatible microcomputer system, a dedicated microcontroller couples a non-compatible keyboard to the system. The keyboard uses a serial bidirectional transmission system including parity bits. The scan codes differ from those of the IBM Personal Computer keyboard, and each key break is represented by two bytes. On receiving data from the keyboard, the microcontroller checks parity and requests re-transmission if a parity error is detected. If a byte of data received is the first of a two-byte key break sequence, the microcontroller waits to receive the second byte before converting the scan code.

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Keyboard Controller

In an IBM Personal Computer compatible microcomputer system, a dedicated microcontroller couples a non-compatible keyboard to the system. The keyboard uses a serial bidirectional transmission system including parity bits. The scan codes differ from those of the IBM Personal Computer keyboard, and each key break is represented by two bytes. On receiving data from the keyboard, the microcontroller checks parity and requests re-transmission if a parity error is detected. If a byte of data received is the first of a two-byte key break sequence, the microcontroller waits to receive the second byte before converting the scan code. All correct code is converted by the microcontroller to IBM Personal Computer keyboard format and is stored in an output buffer which is located at the same I/O address as used by the IBM Personal Computer interface.

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