Browse Prior Art Database

Video Graphic Adapter Port Diagnostic Wrap Plug

IP.com Disclosure Number: IPCOM000109975D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 120K

Publishing Venue

IBM

Related People

Sugi, H: AUTHOR

Abstract

Disclosed is a system that allows diagnostic tests over the Video Graphic Array circuits. The Video Graphic Array circuits are modified in monitor ID detection circuits and synchronization circuits. A test tool is newly made.

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

Video Graphic Adapter Port Diagnostic Wrap Plug

       Disclosed is a system that allows diagnostic tests over
the Video Graphic Array circuits.  The Video Graphic Array circuits
are modified in monitor ID detection circuits and synchronization
circuits.  A test tool is newly made.

      The Video Graphic Adapter interface has monitor identification
pins for the purposes that the personal computers can recognize the
type of currently attached cathode ray tube displays.  Each monitor
identification pin state is conventionally readable through a
read-only monitor identification register.

      These 3 monitor identification pins are used for the diagnostic
purposes.  Each of the 3 monitor identification pins is also
connected through an analog-to-digital converter and to one of "color
test register 0" through "color test register 2".  See Fig. 1.  The
"color test register 0" through "color test register 2" are readable
through the system bus.  The analog-to-digital converter is capable
of recognizing the red or green or blue current value.

      The connections between the 3 monitor identification pins and
monitor identification register are switchable through "diagnostic
enable register".  The connection is made when a "normal" value is
written to "diagnostic enable register" through the system bus.
Theconnection is broken when a "diagnostic" value is written.  The
status of "diagnostic enable register" is readable through the system
bus.  The VGA interface has horizontal synchronization and vertical
synchronization pins.  Both of them are usually driven by output
circuits.

      The horizontal synchronization pin is also connected to
"horizontal synchronization in register".  The pin state is readable
through the register.  The connection between horizontal
synchronization pin and the horizontal synchronization driving
circuits is switchable through the "horizontal synchronization out
enable register".  See Fig. 2.  The connection is made when a
"normal" value is written to the "horizontal synchronization out
enable register".  The connection is broken when a "diagnostic" value
is written.  The status of the "horizontal synchronization out enable
register" is readable through the system bus.

      The vertical synchronization pin is also connected to the
"vertical synchronization in register".  The pin state is readable
through the register.

      The ...