Patent GB-1330748-A (GB)
Title: Apparatus for forming  display of graphical and alphanumeric  data
IPC: G09G5/24
Filed: 1971-09-08
Abstract: 1330748 Cathode-ray tube displays APPLIED DIGITAL DATA SYSTEMS Inc 8 Sept 1971 [9 Sept 1970] 41935/71 Heading H4T In a display system employing a video display device which may, inter alia, comprise a cathode-ray tube, a display consisting of both Alpha-Numeric characters and graphical patterns is produced by directing input data signals including control signals to the appropriate character or graphical pattern signal generator, respectively, the signals produced by which control a video signal generator controlling the ON-OFF condition of the display device. As shown in Fig. 1, coded data specifying the characters and the patterns to be displayed, together with control data, are supplied from a source 10 to a code interpreter 12 which routes the character and pattern data to a memory 14 and the control data to flip-flops (F/F) 16 and 18.  When Alpha-Numeric characters only are to be displayed F/F 16 is reset and the "0" output conditions AND gate 22 to pass character data from memory 14 via OR gate, 30, to a read only memory 32. The latter then produces the corresponding Alpha-Numeric pattern signals which are supplied via OR gate 34 to the video signal generator 36 the output signals from which control the ON and OFF condition of the beam of a cathode-ray display device (e.g. a T.V. monitor) 40 and additionally control the synchronization of the entire system. The resulting Alpha-Numeric characters are then produced as unblanked elements against a blanked background (or vice-versa) in a 5 x 7 dot pattern contained within a 6 Î 9 dot character space as shown in Fig. 3 in respect of the character A. When mixed Alpha-Numeric characters and graphical patterns are to be displayed the control data sets F/F 16 and in accordance with whether characters or graphical patterns are about to be displayed, respectively resets or sets F/F 18. In the latter (set) state the "1" output conditions AND gate 20 to pass character data from memory 14 via the non-inhibiting input of inhibited AND gate 26 to OR gate 30 and the operation proceeds as described above for Alpha-Numeric character display. When, however, graphical patterns are to be displayed F/F 16 remains set and F/F 18 is reset and the "1" output of the latter is fed to memory 14 as additional control data which is supplied to the inhibiting input of AND gate 26 and employed to condition AND gate 24 to pass the graphical pattern data from AND gate 20 to a graphics logic unit 28. The latter interprets the pattern data in terms of the 6 Î 9 dot character space shown in Fig. 4 which is considered to comprise six bit spaces b 1  ... b 6  and controls the video signal generator 36 to selectively blank or unblank the latter spaces, provision also being made to selectively control the nine dot positions within each bit space. When the display device comprises a cathoderay tube (which may be a storage display tube) non-interlaced line scanning which may be either horizontal or vertical is employed and a sinusoidal sweep signal may be included to sweep the scan over the full character height or width respectively. Other display devices may include plasma screens, light-emitting diodes and tungsten light bulb patterns.