Browse Prior Art Database

Display Architecture for Rapid Character Update

IP.com Disclosure Number: IPCOM000040497D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gupta, S: AUTHOR [+2]

Abstract

In an all-points-addressable (APA) display, each bit of a bit buffer memory corresponds to a pixel of the display. An architecture is provided in which memory words in the bit buffer memory are addressed (or mapped) in a vertical arrangement. In addition to the vertical addressing feature, the present invention includes write masking, logical functions, and barrel shifting. Write masking defines which bits in the bit buffer memory can (and cannot) be written over. The vertical arrangement permits the display to use existing microprocessor functions which facilitate the rapid movement of memory words (or blocks of memory words) in memory.

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Display Architecture for Rapid Character Update

In an all-points-addressable (APA) display, each bit of a bit buffer memory corresponds to a pixel of the display. An architecture is provided in which memory words in the bit buffer memory are addressed (or mapped) in a vertical arrangement. In addition to the vertical addressing feature, the present invention includes write masking, logical functions, and barrel shifting. Write masking defines which bits in the bit buffer memory can (and cannot) be written over. The vertical arrangement permits the display to use existing microprocessor functions which facilitate the rapid movement of memory words (or blocks of memory words) in memory. To allow for various conditions, such as the overlapping of contents of one character block with the contents of another, data previously entered for display is logically combined with new data to provide a desired result. Barrel shifting accounts for the difference between the position of a character image as stored in a font table and the relative position the character is to occupy in a character block on a display. For example, in the font memory, a 7-by-7-bit character may be positioned in the lower left of a 16-by-16-bit block in the font table. If transferred to the bit buffer memory, the character will normally be positioned in the lower left of the bit buffer character block. The barrel shifting permits the character to be shifted (horizontally) in the bit buffer memory. Th...