Browse Prior Art Database

Automatic Horizontal Centering Adjustment

IP.com Disclosure Number: IPCOM000112547D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Sohda, M: AUTHOR [+2]

Abstract

In a device which provides a function of converting analog signals of CRT (Cathode Ray Tube) port (like PS/2 monitor interface) to digital signals and timings required for a digital display (like TFT/LCD panel), and which equips with PLL (Phase Lock Loop) to generate a dot clock and ADC (Analog to Digital Converter), it is very severe to display all video data in the limited display resolution of the panel correctly. In case of VGA (Video Graphics Array), the horizontal resolution of the displayed image is 640 dots. On the other hand, the resolution of the panel for VGA is also 640 dots. Hsync (Horizontal Synchronous pulse) provides rough horizontal position of the video image data and it will be varied by displayed modes and PS/2 systems.

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Automatic Horizontal Centering Adjustment

      In a device which provides a function of converting analog
signals of CRT (Cathode Ray Tube) port (like PS/2 monitor interface)
to digital signals and timings required for a digital display (like
TFT/LCD panel), and which equips with PLL (Phase Lock Loop) to
generate a dot clock and ADC (Analog to Digital Converter), it is
very severe to display all video data in the limited display
resolution of the panel correctly.  In case of VGA (Video Graphics
Array), the horizontal resolution of the displayed image is 640 dots.
On the other hand, the resolution of the panel for VGA is also 640
dots.  Hsync (Horizontal Synchronous pulse) provides rough horizontal
position of the video image data and it will be varied by displayed
modes and PS/2 systems.  When the image is displayed in CRT, this
does not cause any trouble because of wide display area of CRT.  But
when the image is displayed in the panel for VGA, user might miss
some video data of the edge of the image from the screen without any
user horizontal position adjustment.

      This article describes a method to adjust the horizontal
position of video image data into the display area of the panel,
automatically.

      Fig. 1 shows an example of the configuration.  It is assumed
here that the resolutions of both the panel and the displayed image
are 640 dots and a signal of "Display Timing" provides an exact
horizontal (/vertical) position of the panel.  The ci...