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Browse Prior Art Database

Keyboard Detection in a Pen-Based Computer System

IP.com Disclosure Number: IPCOM000112754D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Debauche, BJ: AUTHOR [+4]

Abstract

Disclosed is a keyboard interface circuit capable of detecting the attachment of an optional keyboard to a pen-based computer system. While While the computer system typically receives inputs written on its display screen using a stylus, alphanumeric inputs can also be made by means of an attached keyboard. With the keyboard interface circuit, the host processor is ready at all times to receive and process the diagnostic code generated by the keyboard upon the application of electrical power. After the presence of the keyboard is detected, the computer system periodically issues a command to the keyboard. If the keyboard fails to respond to this command, an assumption is made that the keyboard has been disconnected.

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

Keyboard Detection in a Pen-Based Computer System

      Disclosed is a keyboard interface circuit capable of detecting
the attachment of an optional keyboard to a pen-based computer
system.  While While the computer system typically receives inputs
written on its display screen using a stylus, alphanumeric inputs can
also be made by means of an attached keyboard.  With the keyboard
interface circuit, the host processor is ready at all times to
receive and process the diagnostic code generated by the keyboard
upon the application of electrical power.  After the presence of the
keyboard is detected, the computer system periodically issues a
command to the keyboard.  If the keyboard fails to respond to this
command, an assumption is made that the keyboard has been
disconnected.

      Microcode in the service processor of the pen-based computer
system is used with the keyboard interface circuit in the detection
of keyboard presence.  The service processor keeps a 'keyboard
present' flag, which it updates every 25 msec.  The system processor
can query this flag to know instantly whether the keyboard is
attached.  Thus, the system processor is relieved from a need to
communicate directly with the keyboard to determine its presence.

      The Figure shows the keyboard interface circuit 10 on the
system board 12, and the associated interface circuit 14 of the
keyboard 16.  The keyboard is connected to the system board through a
connector 17, which extends at an edge of the system board and at an
aperture of the system cover (not shown) to allow the connection of
an external device.  A cable may also extend between the system board
and the keyboard.  Five-volt power, indicated as KBDVCC, is supplied
by the system to the  key...