Browse Prior Art Database

Data Terminal Using Table Lookup for Display Attributes

IP.com Disclosure Number: IPCOM000052611D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Brooks, EG: AUTHOR [+2]

Abstract

A display refresh buffer has two bytes for every character location, on for a character code to be displayed and another for a pointer into a table which can be loaded with combinations of display attributes.

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Data Terminal Using Table Lookup for Display Attributes

A display refresh buffer has two bytes for every character location, on for a character code to be displayed and another for a pointer into a table which can be loaded with combinations of display attributes.

Data terminal 10 includes a refresh buffer 11 having two bytes of storage for every character location of conventional raster-scanned CRT display 12. Control logic 13 addresses these bytes by pairs and transfers them over a 16-bit data path to 16-bit register 14. The eight bits representing the character code for the display location address a character generator 15, which outputs a serial stream of video dots to CRT display 12.

The remaining eight bits in register 14 form a pointer or index into a tabular memory 16 having 256 addressable locations each holding seven bytes of information. Each table location can therefore specify any combination of up to seven different attributes (such as reverse video, underline, blink, etc.) to be applied to CRT 12 for the character currently being displayed. Table 16 can be loaded with particular combinations at each of its addresses by logic 13 from buffer 11 during a special control sequence of data terminal 10. Storing constant-length pointers rather than variable-length attributes reduces the peak storage size and data-transfer rate required of buffer 11. The number of bits in the pointer can, of course, be made greater or smaller to accommodate a different numb...