Video system controller with a row address override circuit.

摘要

The present invention is a video system which includes a data processor (1), such as a mircoprocessor, for processing data, a video memory (5) for storing data from the data processor corresponding to an image to be displayed, a display (11), such as a raster scan cathode ray tube, for displaying the image data stored in the video memory means, and a video system controller (3) connected to the video memory (5) For controlling the transfer of data from the video memory (5) to the display (11) and between the data processor (1) and the video memory (5). The video memory (5) is preferrably a multiport dynamic randon access memory including an addressable memory array. The video system controller (3) performs a number of functions including refresh of the dynamic random access memory, multiplexing of the various access requests of the video memory and control of the blanking interval of the display. This is accomplished by having a first portion which operates synchronously with the video memory (5) and a second portion which operates synchronously with the data processor (1). The transfer operations in the video system controller are preferrably controlled through the use of a programmable state machine which manipulate inputs in a logic array. <IMAGE>