Selective control of window related overlays and underlays

摘要

Apparatus and methods for selectively controlling by window the number of overlay planes, the number of overlay palettes, and the overlay/underlay plane masks in a graphics video display system. A logic/multiplex control translates overlay and underlay data patterns from a multiple plane VRAM (Video Random Access Memory), referenced to the graphics system frame buffer, into window specific patterns. The window related translation is conveyed to conventional RAMDACs (Random Access Memory Digital-to-Analog Converters) for raster scan synchronized digital-to-analog conversion. The translation as provided by the controller is responsive to data selectively and dynamically written into a random access memory, thus providing translation of overlay/underlay data into window distinct and selective overlay/underlay palette functions.