Abstract: A cursor circuit for an on-the-fly digital television display system. The host digital television display system employs an intermediate buffer which stores a coded representation of the symbol only during the period of its display. In order to obtain access of the encoded symbol in storage with a conventional light pen, the circuit secures the identity of the encoded symbol in the intermediate buffer during the first display frame. This identity is the address of the symbol as stored in a refresh buffer. This identity is made available for accessing the refresh buffer during a second display frame. This enables convenient access of the encoded symbol in an on-the-fly digital television display.

Abstract: A video generator is disclosed for use in a digital television display system, for converting randomly occurring data signals representing graphical patterns into a time-sequential video signal for use with a sequentially line scanned display device. The circuit is comprised of a threaded buffer connected to receive the data signals and adapted to sort the data signals into groups ordered by extremal scan line positions for the pattern represented. An intermediate buffer has a first input connected to the output of the threaded refresh buffer for storing the ordered data signals once during each display field before the display of the pattern represented and outputting the ordered data signals in synchronism with the line scans of the display. A graphical pattern generator is connected to the output of the intermediate buffer for decoding the ordered data signals outputted therefrom and generating on a first output line components of the pattern represented which lie along the display line to be scanned.

Abstract: Apparatus is disclosed to implement a recursive technique to generate the coordinates of horizontal raster line components which intersect a conic-section shape to be represented. The apparatus cooperates with a refresh buffer which stores the video data in coded form to be read out ordered by raster line location and an intermediate buffer which permits these coded data to be read as many times as is needed during the course of displaying one frame of pictorial information, and then to be dropped, and a partial raster assembly storage which permits data to be written randomly along a given raster line.