With a data display terminal having an electron beam tube, an image repetition memory serves for cyclically regenerating the display. With a change of the display, a complete overwriting can be necessary. However, the overwriting of the image repetition memory cannot interrupt the regeneration operation. The beam flyback times during an image cycle do not suffice in order to overwrite the entire image repetition memory. Therefore, data are written into the image repetition memory during a forward line scan and are simultaneously written into a line buffer designed as a clock interface. With this technique, an entire image repetition memory can be written during an image cycle.
A method and apparatus for improving bandwidth of sequential access to a display data memory. Display data and tag information related to consecutive data repetitions are stored. No display memory access is needed to output data to the CRT during the time periods when data is being repeated, thus increasing display memory bandwidth. Display data from a location in display memory is stored in a latch, and is output from the latch until the tag information indicates no more data repetitions occur.
