Browse Prior Art Database

Keyboard Simulator Circuit

IP.com Disclosure Number: IPCOM000036647D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Villar, BJ: AUTHOR

Abstract

This article describes a circuit arrangement which allows a personal computer (PC) to initial program load (IPL) error-free without a keyboard attached for applications where tampering is to be prevented such as in token ring bridges and/or where space is limited.

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Keyboard Simulator Circuit

This article describes a circuit arrangement which allows a personal computer (PC) to initial program load (IPL) error-free without a keyboard attached for applications where tampering is to be prevented such as in token ring bridges and/or where space is limited.

In this application PC systems will be used as token ring bridges in local area network applications which must resist tampering for security reasons. These PC systems may also be mounted in a rack with no space for a keyboard, thus the need for a small keyboard simulator.

The keyboard simulator circuit of this disclosure contains a microprocessor which is programmed to deliver the same handshaking signals that the keyboard provides during the CPU's power-on self-test (POST) sequence. It will allow for error-free IPL in case primary power is interrupted or the unit is turned off for maintenance or updates. This circuit with minor microcode changes also can be used on any PC system with an intelligent keyboard. A light-emitting diode (LED) indicator on the keyboard simulator box lights up when the CPU has completed its POST and is used as a power as well as good signal indicating all handshaking signals have been received.

The circuit is shown in the drawing. This circuit communicates with the PC through the standard keyboard port from where it also receives its power, providing all responses required by the POST.

After an initial power-on-test, the microprocessor IC1 monitors...