CHARACTER DISPLAY SYSTEM

专利名称：CHARACTER DISPLAY SYSTEM申请号：AU4260072申请日：19720523公开号：AU432676B2公开日：19730201

摘要：1,224,224. Cathode-ray tube displays. SANDERS ASSOCIATES Inc. 30 Aug., 1968[1 Sept., 1967], No. 41633/68. Heading H4T. In an arrangement for tracing characters onthe screen of a cathode-ray tube each character is composed of a string of strokeschosen from a repertoire of strokes extending in various directions. Fourteen strokes a,a1, b to f, g, g1, h to k and m (Fig. 2) having twelve different directions are provided thetracing of which requires component deflections of + X,- X, + 2X, - 2X, + 2Y and - 2Y. Eachcharacter is traced in a space 26 (see also Figs. 1 and 3A) having X and Y dimensionscorresponding respectively to eight units of deflections and the lower left-hand cornerof which constitutes the origin at which the tracing commences. The different charactersare identified by signals contained in a memory 32 (Fig. 1) from which, on request, they aresupplied via a register 34 to a decoder 46 which provides output signals on individuallines indicative of the different characters. The latter signals are then supplied, togetherwith signals from a clock 50, to a gate matrix 48 which generates a succession of timedsignals selected one of which are supplied to the horizontal and vertical ramp generators52; 57 respectively and to an unblanking amplifier 62. The outputs of the rampgenerators are then combined in summing amplifiers 42, 40 with signals from apositioning circuit 36 (controlling the gross position of the character) and fed to the Xand Y deflection control means 22. Fig. 3A, shows the sequence of steps in tracing the

character A. Thus, commencing at the lower left hand corner, four of the c strokes (of therepertoire shown in Fig. 2) are produced during four clock pulses followed by four kstrokes during the next four clock pulses after which two e strokes (superimposed onthe last two k strokes) and two g strokes complete the character. All the deflectionsignals required for tracing this pattern are produced by a portion of matrix generator48 which is concerned solely with character A and which additionally produces unblankingsignals so that the beam remains blanked whilst being directed to the origin and duringthe two strokes e (which retrace the last two k strokes in the opposite direction) in orderto maintain uniformity of illumination. The character B (Fig. 3B) is traced in a similarmanner. Fig. 5, shows the gate matrix 48 of Fig. 1 including the portion 48-A concernedwith the tracing of the character A. Such portion comprises a number, five, of AND gates70, such number being determined by the changes required in stroke direction and inbeam unblanking when tracing the character. All the of gates receive as a first input aconstant signal on output line 46-A of decoder 46 (identifying the character A) and haveas second inputs various sequencies of the timing pulses from clock 50 (Fig. 1)

commencing with pulse T10 (pulses T1 to T9 allowing time for the positioning circuit 36to effect the required shift). During the interval T10 AND gate 70-1 produces an outputpulse which is fed to OR gates 74a, 74e and 74g. Likewise during the intervals T14, T18,T25 and T22 the other AND gates 70 produce output pulses which are supplied to thevarious OR gates 74a to 74g as shown. Of the latter gates, 74a to 74f inclusive areconcerned respectively with controlling deflections of +X, -X, +2X, - 2X, +2Y and -2Y unitsand gate 74g is concerned with unblanking requirements. The outputs of all these gatesare fed to similar respective bi-stable circuits 80a ... 80g comprising conventional bi-stableflip-flops with gated inputs the outputs from the bi-stable circuits being utilized tocontrol the appropriate deflection and blanking circuits. The arrangement operates asfollows. Considering circuit 80a (the operation of the others being identical), the outputpulse from OR gate 74a during period T10 (curve 78, Fig. 6) together with the negativetransition of a pulse train T s (from clock 50) causes the flip-flop FF to change its state

and produce an output 83 on line 81d which is maintained until the next output pulsefrom gate 74a during period T18. The output on line 81d controlling the +X deflection issupplied to input 51a of the horizontal ramp generator 52 which then generates adeflection signal having a slope 67 one unit (see 85a, Fig. 7) and which corresponds to thehorizontal component of the c and k strokes 1-8 (Fig. 3A). Simultaneously, i.e. duringperiod T10, the output from AND gate 70-1 is applied to OR gate 74e the output fromwhich is applied to bi-stable circuit 80e which controls the vertical ramp generator 57 toproduce a deflection (104a, Fig. 7) signal having a slope of two units (+2Y) correspondingto the vertical component of the c strokes 1-4 (Fig. 3A). This deflection signal ismaintained until period T14 when the next input to OR gate 74e terminates theproduction of this deflection signal. The latter input (from AND gate 70-5) is aslosupplied to OR gate 74f which then controls bi-stable circuit 80f to produce a deflectionsignal (104b, Fig. 7) having a negative scope of two units (-2Y) corresponding to thevertical component of the k strokes 5-8 (Fig. 3A) and which is maintained until the nextinput to OR gate 74f during period T18 from AND gate 70-9. During period T10 theoutput from AND gate 70-1 is also supplied to OR gate 74g which supplies an output tobi-stable circuit 80g to unblank the beam so that the c and k strokes are visible on thetube screen. At period T18, however, when the output of AND gate 70-9 is employed tocontrol the tracing of the e strokes 9 and 10 (Fig. 3A) by utilizing inputs to OR gates 74aand 74b to terminate the + X and - 2Y deflection signals and inputs to OR gates 74b and74e to produce the - X and + 2Y deflection signals required for the e strokes, an input isalso supplied to OR gate 74g which terminates the unblanking output of bi-stable circuit80g so that the e strokes, which retrace k strokes 8 and 7 are blanked out. The g strokes11 and 12 are then traced during period T20 the beam being again unblanked and duringperiod T22 the beam is again blanked which it is being returned to the origin on i stroke13. Other characters are traced in similar manner by supplying the appropriate decoderoutput 46-A to 46-N to the corresponding section 48A to 48N of the gate matrix. At the

end of the tracing of a character the cessation of an output signal from an OR gate 150having inputs from each of the bi-stable circuits 8a ... 80b operates via an inverter 151 toreset the clock 50 so that the next timing signal is a T41 signal (the last of the cyclicoutput pulses from the clock) which prepares the system to display the next character.The matrix sections 48-A to 48-N comprise individual plug-in modules so that thecharacter set may be readily changed, the clock cycle being enlarged if the new characterset involves larger or more complex characters. A reduction in the number ofcomponents utilized in the matrix sections of Fig. 5 may be effected by taking intoaccount the fact that many characters of a set require the same combination of strokecomponents and unblanking during the same stroke interval (Fig. 8, not shown). Areduction in the number of such components may also be effected by modifying theclock and distributer 50 (Fig. 1) so that it produces timing signals defining 2, 3, 4, or morestroke intervals (Fig. 9, not shown) and modifying the matrix sections to utilize suchtiming signals (Fig. 11 not shown).

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