Abstract :
An attempt is being made to produce low-cost real-time displays by utilizing the much improved performance of the latest range of 16 and 32-bit microprocessors. The Video Display Processor (VDP) section of these displays must operate at speeds which necessitate the use of special purpose TTL circuitry. If conventional pixel mapped frame buffers are used in the VDPs this results in large memories and a considerable amount of TTL circuitry to enable the rapid filling of these memories. Frame buffer size and associated circuitry can be drastically reduced by using run length encoding. Duplication of frame buffers allows access to one buffer by the screen refresh circuitry whilst giving unrestricted access to the other buffer by the filling circuitry. Whilst this doubles the memory size, the consequent increase in available filling time allows the use of slower memories and simplifies the control circuitry. This paper describes a VDP using run length encoding and dual frame buffers which satisfies the criteria of fast operation and low cost.
