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Nine Dot Line Drawing Character Generation with Eight Bit Wide Character Generator

IP.com Disclosure Number: IPCOM000045274D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Miwa, I: AUTHOR [+2]

Abstract

The 9th dot of a 9-dot line drawing character is generated from an 8-bit wide character generator by ANDing a line drawing character attribute bit and the 8th bit of an 8-bit output from the character generator.

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Nine Dot Line Drawing Character Generation with Eight Bit Wide Character Generator

The 9th dot of a 9-dot line drawing character is generated from an 8-bit wide character generator by ANDing a line drawing character attribute bit and the 8th bit of an 8-bit output from the character generator.

Some raster scan CRT character displays use a character generator to generate relatively simple business graphics, such as a table or bar chart. Some basic line drawing characters or graphic characters, which are required to compose graphic patterns, are stored in the character generator and used to display line segments at addressed character boxes on the screen. In recent character displays, a 9x16-dot character box is used to display a character. However, commercially available character generators are generally 8-bit wide. Therefore, in order to generate 9-dot line drawing characters with such an 8-bit wide character generator and thus display lines without discontinuities between character boxes, an additional one bit must be generated for the 9th dot.

The figure shows a circuit to do this. The refresh buffer stores a line drawing character bit as a character attribute for each character code, which is set ON when a line drawing character is to be generated. The attribute bit from the refresh buffer and the 8th bit of the 8-bit output from the character generator ROS (read-only store) are applied to an AND gate with its output connected to the serializer shift register...