Browse Prior Art Database

Low-Cost Analog Drive Circuit for Monochrome Analog Cathode Ray Tube Displays

IP.com Disclosure Number: IPCOM000035096D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 59K

Publishing Venue

IBM

Related People

Baldwin, DM: AUTHOR [+2]

Abstract

There have been developed Analog Cathode Ray Tube (CRT) Controllers for controlling video CRT output. These controllers consist mainly of gate arrays, memory, and a Video Digital-to-Analog Converter (DAC). The controllers will drive both color and monochrome CRT's. In one color application, the Video DAC provides extensive control of display colors, allowing the use of 256 colors similtaneously. In the monochrome application, the Video DAC allows the use of 64 shades of gray.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 3

Low-Cost Analog Drive Circuit for Monochrome Analog Cathode Ray Tube Displays

There have been developed Analog Cathode Ray Tube (CRT) Controllers for controlling video CRT output. These controllers consist mainly of gate arrays, memory, and a Video Digital-to-Analog Converter (DAC). The controllers will drive both color and monochrome CRT's. In one color application, the Video DAC provides extensive control of display colors, allowing the use of 256 colors similtaneously. In the monochrome application, the Video DAC allows the use of 64 shades of gray.

Conventionally, however, monochrome CRTs have been digitally controlled, and offer only two shades of gray: normal and high intensity. The above sophisticated and expensive CRT controllers are not required for these, and the present invention provides a simple Analog Drive circuit that replaces the Video DAC in the CRT Controller described above for applications where two shades of gray are adequate and color support is not required.

Fig. 1 shows an overview of the prior CRT control circuit for color. Three main groups of signals interface the Video DAC to the control circuit: Palette (PA0-PA7), Control, and Data (DB0-DB7). Through this interface, extensive control of the DAC is possible. In the color mode, 256 colors may be programmed (and then displayed) from a total of 260,000 colors. As indicated above, in monochrome mode 64 shades of gray may be accessed. In a color mode, the DAC drives the CRT with 3 analog video signals: Red, Green, and Blue. In the monochrome mode, only the Green signal is used.

As shown in Fig. 2, an Analog Driver circuit replaces the DAC for monochrome applicatio...