Browse Prior Art Database

Color Display Window Control

IP.com Disclosure Number: IPCOM000062352D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Beaven, PA: AUTHOR

Abstract

In a color graphics display, a multiplane all-points-addressable (APA) buffer controls a palette from which an analog video signal is generated to drive a CRT. As disclosed, partitioning or windowing is provided by an additional APA plane which is used to control the source of displayed data. This source can be selected either from other APA planes or from digital or analog ports. Fig. 1 shows an APA graphics adapter providing video signals to a raster-scanned CRT display. If the APA buffer contains n planes, each picture element (pel) on the display can assume one of 2n colors, as determined by a mapping contained in a palette store. The palette store output is passed through a digital-to-analog converter (DAC) to provide analog video for a display monitor.

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Color Display Window Control

In a color graphics display, a multiplane all-points-addressable (APA) buffer controls a palette from which an analog video signal is generated to drive a CRT. As disclosed, partitioning or windowing is provided by an additional APA plane which is used to control the source of displayed data. This source can be selected either from other APA planes or from digital or analog ports. Fig. 1 shows an APA graphics adapter providing video signals to a raster-scanned CRT display. If the APA buffer contains n planes, each picture element (pel) on the display can assume one of 2n colors, as determined by a mapping contained in a palette store. The palette store output is passed through a digital-to-analog converter (DAC) to provide analog video for a display monitor. Graphics update algorithms, screen regeneration, CRT function, APA support functions and a PC bus interface are provided by the APA controller. Two additional planes are provided for character shape and an attribute code to control the character appearance. In Fig. 2, one additional plane, the control plane, is encoded with information to select the source of video data to be transmitted to the display. For example, a byte of the control plane could be coded to select from: - all remaining APA plans - a subset of the APA plans - video port 1 (see Fig. 2) - video port 2 - video port 3. Further encodings are possible. For example, - mix two sources of video according to a defined se...