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(11) | EP 0 182 454 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Video system controller with a row address override circuit |
| (57) The present invention is a video system which includes a data processor (1), such
as a microprocessor, 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 manipulates inputs in a logic array. |