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Browse Prior Art Database

Automatic Video Frequency / Mode Detection and Adjustment

IP.com Disclosure Number: IPCOM000115021D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 68K

Publishing Venue

IBM

Related People

Nishimura, H: AUTHOR [+3]

Abstract

This article describes a method to detect video frequency and mode, and to set the proper video parameters for adjustment to display the best screen image automatically on CRT compatible LCD units.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 64% of the total text.

Automatic Video Frequency / Mode Detection and Adjustment

      This article describes a method to detect video frequency and
mode, and to set the proper video parameters for adjustment to
display
the best screen image automatically on CRT compatible LCD units.

      Considering CRT compatible LCD units, the video interface is
analog interface, and dot clock is not supplied from the attached
systems though dot clock is needed to drive the video data on LCD
panel.

      Video frequency/mode detection is required to reproduce dot
clock by PLL (Phase Locked Loop) circuits, and to set proper video
parameters for displaying the clear screen image on CRT compatible
LCD units.

      Three parameters are measured by base clock, H-sync and V-sync
signals for video frequency/mode detection.  Comparing H-sync signal,
base clock should be rather too fast, and is equipped on CRT
compatible LCD units.  The parameters are defined as "W", "X" and "Y"
and they are shown in Fig. 1 (a), (b) and (c) respectively.

      Definition of "W" is H-sync period counted by base clock,
definition of "X" is total line numbers and definition of "Y" is
H-sync pulse width counted by base clock.

Flow for video frequency/mode detection and adjustment is described
below (Fig. 2).
  1.  Detecting parameters W/X/Y from H/V-sync signals of the
attached
       system.
  2.  Controller searches W/X/Y combination from memory for video
       frequency/mode detection.  W/X/Y...