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Browse Prior Art Database

Display System Having Overlay Synthesis Circuitry

IP.com Disclosure Number: IPCOM000112329D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Miyazaki, Y: AUTHOR [+2]

Abstract

Disclosed is a overlay and a background image synthesis circuit using a color palette digital analog converter. This overlay synthesis circuit forces or modifies the background image data by the overlay data or by background data itself.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 75% of the total text.

Display System Having Overlay Synthesis Circuitry

      Disclosed is a overlay and a background image synthesis circuit
using a color palette digital analog converter.  This overlay
synthesis circuit forces or modifies the background image data by the
overlay data or by background data itself.

      Fig. 1 shows color palette digital analog converter (1),
background image data memory (2), overlay data memory (3), overlay
synthesis circuitry (4) and central processing unit (5).

      The central processing unit (5) refreshes the overlay memory
independently from background image data memory to draw lines or
characters.

      The overlay data from the overlay memory (3) forces the
background data from the background memory (2) to a reserved data in
the overlay synthesis circuitry (4).  This forced data addresses a
reserved area of the color palette, then digital analog converter (1)
outputs the value in the palette as a overlay color to any display
monitor.

      The force data value reserves some color palette address for
overlay color.  When background data value is same as a overlay
reserved value, the overlay synthesis circuit modifies background
data to unreserved value for not confounding background and overlay
data.

      Fig. 2 shows the reserved value is 255 and the overlay data is
active then the overlay synthesis circuit forces any background data
to 255.  If overlay data is inactive and image data is 255 then the
overlay synthesis...