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Browse Prior Art Database

Liquid Crystal Display Subsystem Failure Isolation Method

IP.com Disclosure Number: IPCOM000111332D
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2005-Mar-26
Document File: 2 page(s) / 94K

Publishing Venue

IBM

Related People

Rodriques, L: AUTHOR [+2]

Abstract

Described is a hardware implementation to provide a manufacturing test method of isolating Liquid Crystal Display (LCD) subsystems and drive video subsystems, as used in tablet or lap top type of Personal Computer (PC) systems.

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

Liquid Crystal Display Subsystem Failure Isolation Method

      Described is a hardware implementation to provide a
manufacturing test method of isolating Liquid Crystal Display (LCD)
subsystems and drive video subsystems, as used in tablet or lap top
type of Personal Computer (PC) systems.

      Typically, when a failure occurs on a tablet or lap top PC
system that causes the video to fail, difficulty can be experienced
in determining what subsystem caused the failure.  Since the
diagnostics relys on the screen to show error codes, a blank or
distorted screen makes such codes useless.  The concept described
herein provides a way to isolate the LCD subsystem and the video
subsystem driving it.  A circuit is implemented to isolate failures
between an LCD subsystem and a system planar video subsystem.  The
circuit provides an LCD generated data pattern to be inserted to the
LCD's data bus.  This pattern, together with the video clocks from
the subsystem, displays a black and white self test pattern if the
LCD subsystem is functioning properly.  A test mode is activated by a
signal generated by the planar which is activated by using the
brightness/contrast controls of the system.

      In the prior art, when there was a video failure that was not
detected during Power-On System Test (POST) procedures, the failing
subsystem could be isolated by inserting data into the LCD data bus.
By driving the LCD data bus high and low while maintaining the clock
signals to the LCD panel, alternating black and white patterns could
be displayed.  If the patterns were displayed correctly, the LCD
subsystem was considered OK and the failure could be determined to be
in the video subsystem driving the display.  If the pattern was
distorted with missing or different intensity rows or columns, the
failure would be in the LCD.  However, if the LCD display and the
video subsystem driving the display both failed to show a working
image, it was impossible to determine if the LCD panel or the driving
electronics failed.

      The concept de...