Graphic display system containing a video direct access memory with a shared slider register and a running counter

摘要

A graphics system includes a random access memory (105) with a split serial register (109) having low and high halves of a plurality of storage elements, an access start point address register (137), and an arrangement (140, 142, 145) for stopping an access run at the end of a predetermined run length. Thus, there are specified both start and stop point addresses for a read data access operation from the split serial register in a graphics processing system. By using these start and stop point addresses, the operating speed of the graphics processing system is increased. The random access memory also includes a multiplexer (160) for coupling a column of storage cells from the memory array to storage elements of the split serial register (109). Data stored in either a low half or a high half of the addresses of the memory array may be selectively coupled through the multiplexer to either a low half or a high half of the split serial register. For a tile oriented graphics display operation, this arrangement increases the number of choices of where within the random access memory array to store specific bits of the tile data to be displayed. Data representing a tile can be mapped into a single row of the random access memory array. IMAGE