Browse Prior Art Database

Keyboard Port Adapter for Personal Computers

IP.com Disclosure Number: IPCOM000106799D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 113K

Publishing Venue

IBM

Related People

Kangas, PD: AUTHOR

Abstract

Disclosed is an attachment for Personal Computer (PC) systems that provides a Keyboard Port Adapter (KPA) to enable Input/Output (I/O) port expansion for peripheral device attachment without interfering with normal keyboard operation.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Keyboard Port Adapter for Personal Computers

      Disclosed is an attachment for Personal Computer (PC) systems
that provides a Keyboard Port Adapter (KPA) to enable Input/Output
(I/O) port expansion for peripheral device attachment without
interfering with normal keyboard operation.

      PC systems often use up all available I/O ports when connecting
various peripheral devices.  When all of the ports are used up, the
usual solution is to add expansion circuit cards, or similar devices,
so as to increase the number of I/O ports to enable the number of
peripheral devices that can be added to a system.  However, this is
not always possible due to the limited number of card slots available
in a system.

      In order to eliminate the need to add expansion circuit cards
but to enable additional devices to be added, the concept described
herein provides a means whereby the keyboard port of a PC can be
multiplexed through the addition of a KPA.  This provides an
additional I/O port without interfering with the existing keyboard
operation, or the need for additional expansion circuit cards.  The
KPA may be used to communicate with either an intelligent peripheral
device, or to directly drive an indicator panel or like device.  The
KPA can also be used to drive a lighted status panel for telephone
equipment as well as other applications.

      Fig. 1 shows a block diagram of a PC system with the KPA
installed in series with the keyboard and the added peripheral
device.  Circuitry within the KPA will relay data to and from the
keyboard and also transmit data to the added external peripheral
device.  The Central Processing Unit (CPU) within the PC will
periodically transmit a control byte to the keyboard for various
functions, such as to turn on or off various keyboard function
lights, such as the cap or num lock lights and to set the typomatic
rate and delay.  The keyboard responds to a small number of character
codes, but a majority are not used.  These unused codes are used by
the KPA to communicate with the external attached peripheral.  The
KPA is different from "wedge" type adapter devices in that it
provides a general purpose output function rather than keyboard
emulation for the input device.

      Fig. 2 shows...