Digital indicia generator employing compressed data

Abstract

A display indicia generator driven by compressed data is arranged to draw indicia on a display coordinated with signals from an external environment. For drawing a line, for example, the compressed data includes coordinates of a point on the line, a slope of the line and a length of the line. The display includes a deflection system for deflecting a writing beam, such as a cathode ray beam, over the display area in a predetermined pattern, i.e., a raster scan or PPI display. The signal source for the external signals to be displayed is coupled via a mixer to the unblanking control of the display. Another input to the mixer comes from the indicia generator which is arranged to enable the beam when it reaches a point, such as the start point on the line. On each succeeding coordinate scan, counters keep track of the portion of the sweep during which the beam should be unblanked so as to display the line. At the completion of the frame, the indicia has been generated concurrently with the signals. Both raster scan and PPI scan embodiments are disclosed.