Patent GB-1330548-A (GB)
Title: Data idsplay systems
IPC: G09G1/10
Filed: 1971-08-20
Abstract: 1330548 Cathode-ray tube displays SIEMENS AG 20 Aug 1971 [25 Aug 1970] 39102/71 Heading H4T In a data display system in which characters formed from one or more straight lines are displayed on the screen of a cathode-ray tube by producing unit (X, Y) deflections of the beam within a notional co-ordinate grid which has the same shape and dimensions for each character, the operation is controlled by an image-generator which includes a fixed-value store containing a separate information block, each having the same number of words, for each character, a desired block address is selected by signals from an image repeater store which, driven by a synchronous counter, repeatedly and successively supplies signals indicating the characters to be displayed, the address of a word within a block is determined by the synchronous or another counter and the output of the fixed value store is supplied to a read-out register which supplies an output describing the beam control required to display the selected character. As shown in Fig. 1, coded (7-bits and parity bit character) indicating signals derived from the image-repeater store (not shown) are fed serially to a shift register 11 which supplies a 7- bit output to a recoder 12 supplying one 6-bit output comprising control signals (e.g. beam bright-up signals) to a logic circuit 13 and a second 6-bit output comprising character indicating signals to the fixed value store 14. A character code Zc (see Figs 2a and 2b which show two possible organizations of the store 14) comprising the latter output addresses the required block B1-B64 and the count Z of the synchronous counter 15 (of the image repeater store), which supplies a 5-bit output, addresses the required word W. The store 14, which comprises a pre-wired magnetic core store then supplies, via a readout register 16, a 4-bit output specifying (see Fig. 3a) the sign and magnitude (= stroke or no stroke) Vx, V and Vy, Y of the X and Y deflections respectively required to trace the character, to a logic circuit 21 which produces the actual beam deflection quantities TX, TY and additionally, supplies a single bit output, specifying beam blank-unblank H/D, to the logic circuit 13. The 4-bit output from readout register 16 is also supplied to position registers 17, 18 which, via respective D-A converters 19, 20, provide outputs HSx, HSy for holding the beam at required positions within a character and because the time of reproduction of each character is constant (since each character consists of the same number of words) the position of a character on the screen is indicated by the count of counter 15 and such count is supplied via switch 24 (closed except during frame (BR) and line (ZR) fly-back) to a D-A converter 22 which provides outputs Hx, Hy for holding the character grid at successive positions on the screen during the tracing of a character, whilst the last character element W20 operates to displace the beam to the origin An from which the tracing of the next character commences. During frame and line fly-back periods the signals producing the latter via D-A converter 23 open switch 24 to interrupt the count supplied to D-A converter for the fly-back intervals. Fig. 3a, shows the pattern of the 5-bit output from read-out register 16 (Fig. 1) for word elements W1-W20 concerned in the tracing of the character A (Fig. 3b). Details of the logic circuits 13 and 21 are described with respect to Fig. 4 (not shown) and of the position registers 17 and 18 with respect to Figs. 5a and 5b respectively (neither shown).