DIGITAL VIDEO DISPLAY SYSTEM USING CATHODE-RAY TUBE

A digital video display system (DVDS) is disclosed for display of image, alphanumeric and other data on a cathode-ray tube (CRT) with sequential raster scan and two, four or eight gray shades. The DVDS includes a central processing unit for activating the system, selecting the X (horizontal axis) and Z (intensity modulation) modes, and designating the starting location of two successive rasters of data from a memory accessed by a data multiplexer subsystem (DMS). At the end of each raster, the DMS interrupts the computer for a new starting location of a raster of data to follow the next while a DVDS control subsystem is prepared for the next raster. The first word of raster data designates the Y-axis value to be transmitted to the CRT vertical deflection system through a static digital-to-analog converter. Each word thereafter contains a predetermined number n of bits for n/3, n/2 or n/1 display elements (DE) in the respective eight, four and two gray shade modes. DE groups are transmitted to the CRT intensity control through a static digital level select network. As each DE group is read, an X-axis integrator is incremented by one, two or four units depending upon the X-axis mode selected. A counter determines when all DE groups of a word have been displayed in each of the gray shade modes, and resets all of the DVDS, thereby shutting off display after one, two or three DMS-memory cycles in the eight, four and two gray shade modes, respectively, until the next word is automatically read out of memory as a separate counter in the DVDS keeps track of the DMS-memory cycles for the different gray shade modes.