Display refresh memory apparatus utilizing one half frame updating

摘要

Refresh memory apparatus for use in a CRT raster display system utilizes half field storage memories for ping ponging between updating and readout. In one TV mode of operation the even and odd raster lines are stored in the respective memories and in another TV mode the top and bottom halves of the frame are stored therein. The most significant bit and least significant bit of the vertical address signals are multiplexed to control the ping pong reading and writing of the memories and are multiplexed with the remainder of the address signal to provide the read and write addresses for the memories. The multiplexers are controlled in accordance with the TV mode in which the system is operating.