Reduced Logic for Boolean Operations on Raster Display Refresh Buffers
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Raster graphics displays commonly employ a refresh buffer, a large RAM (random-access memory) storage comprising one or more frame buffers. Each frame buffer consists of a rectangular array of bitlists, one bitlist per separately illuminable point (pixel) on the display screen. These bitlists or lists of bits each represent a greyscale or color index, an index into a video lookup table. This article describes a mechanism whereby the hardware logic associated with changing the contents of frame buffers is reduced, saving card space (real-estate) and cost. This becomes particularly important in the case of a very high performance design which: (a) Provides the full set of sixteen boolean operators: Bitlist-NEW < -- Bitlist-OLD boolop Current-Color (b) Provides for flexible assignment of the RAM storage into frame buffers.