Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Cathode Ray Tube Video Refresher

IP.com Disclosure Number: IPCOM000077519D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 4 page(s) / 81K

Publishing Venue

IBM

Related People

Rittenhouse, LE: AUTHOR [+2]

Abstract

There is described herein a system for refreshing a raster scanned cathode-ray tube (CRT) display terminal system. The system provides the capability for displaying both characters and vectors. In the system, there is utilized a "line buffer" which contains commands to specify one horizontal line of the display raster. The commands in the line buffer are updated with only those changes required to draw the next line. Those commands for sections of the raster line that are not changed remain unmodified.

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 39% of the total text.

Page 1 of 4

Cathode Ray Tube Video Refresher

There is described herein a system for refreshing a raster scanned cathode- ray tube (CRT) display terminal system. The system provides the capability for displaying both characters and vectors. In the system, there is utilized a "line buffer" which contains commands to specify one horizontal line of the display raster. The commands in the line buffer are updated with only those changes required to draw the next line. Those commands for sections of the raster line that are not changed remain unmodified.

The system effects the minimizing of the command traffic from the memory of the controlling central processor to provide for displaying both characters and vectors, and to provide local modification of commands in the line buffer without requiring communication with the central processor unit.

In Fig. 1, there is shown a block diagram of the system. It contains a computer 10 which is depicted as comprising a CPU 12 which communicates with a main storage 14. Main storage 14 retains the list of display commands. A control logic stage 16 intercommunicates with the main storage 14 and controls a display line buffer 18. The display line buffer 18, in turn provides an input to the display control stage 20, the output of display control 20 being the composite video signal which is displayed in display unit 22 that may suitably be a raster scanned CRT terminal, as is utilized in a conventional interactive graphics system. The list of display commands is stored in main storage 14 and managed by CPU 12. The display commands can be transferred to control logic 16 under cycle-steal control arrangement.

The control logic stage 16 decodes the control portion of a command and places the command in the proper place of the display line buffer. In addition, control logic stage 16 provides the local modification of the commands in the display line buffer when such modification is required.

The display control stage 20 decodes the commands in the display line buffer and generates the composite video signal for display unit 22. This composite video signal contains the line intensity as an analog voltage mixed with the horizontal or line, and vertical or frame synchronization pulses. The display control stage 20 also signals the control logic when the display line buffer is to be updated. Suitably, the display unit 22 can be a raster scanned CRT display unit similar to a television monitor.

Within the contemplation of the operation of the system shown in Fig. 1, there can be carried out the technique of loading display line buffer 18 with display commands and commands to locally modify the display line buffer. Thus, commands transferred to display line buffer can include commands for a display line and for changes in the display line. Also, within the contemplation of the operation of the system, there may be carried out a method for decoding characters where a representation, such as an eight-bit representation for a ch...