Browse Prior Art Database

Display Clearing Method

IP.com Disclosure Number: IPCOM000074462D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Cummins, DA: AUTHOR

Abstract

This is a method of selectively clearing positions of a video display that are not necessarily on integral line boundaries and also provides a method of erasing several displays concurrently.

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Display Clearing Method

This is a method of selectively clearing positions of a video display that are not necessarily on integral line boundaries and also provides a method of erasing several displays concurrently.

The arrangement shown in Drawing A provides for refreshing several video displays sequentially from a core storage unit 5. The data is accessed in a line sequence, i.e., character line 1 display 1, line 1 display 2, line 1 display 3,..., line 2 display 1, line 2 display 2, etc. The data is read into the storage data register (SDR) 8 and is passed to the displays. The program control unit can alter the data in storage via the storage address register 7 and the SDR. If the program requires to blank a section of the screen, two special characters are written into the core storage. These are the "START ERASE" and the "END ERASE" characters and are written into the storage location containing the first character to be erased and the last character to be erased, respectively. When the Control Decode 9 reads the start erase character, it forces a blank character back into storage and passes a blank character to the display currently being refreshed. In addition, it sets a "1" into the shift register 11. The remaining characters for the line currently being refreshed are forced to a blank. The following line in storage is associated with another display that is not necessarily to be erased, so the erase function is stored in the shift register 11. The shift r...