Image Number 5 for United States Patent #4897812.
A graphics adapter of the type whose operation is controlled by control data stored therein. The graphics adapter has two sets of loadable control data, one of which is used by a graphics processor in the graphics adaptor and the other of which is used by the processor for the system in which the graphics adapter is used. Because each processor has its own set of control data, control of the graphics adapter is rapidly and easily switched between the processors. Included in the graphics adapter is graphics control apparatus which contains storage for two sets of control data and operates under control of one or the other of them as determined by signals from the graphics adapter. The graphics control apparatus further includes state storage for retaining state necessary for resumption of operation for one processor after the other has used the graphics adapter. The graphics control apparatus can perform both byte and word operations and can emulate byte operations while operating in word mode. Further, the graphics control apparatus may employ either an external or an internal mask to mask data.