GB1471284A - Method and apparatus for generating a travelling display - Google Patents

Abstract

1471284 Control of displays BUNKER RAMO CORP 27 June 1974 [27 July 1973] 28632/74 Addition to 1395922 Heading G4H A cyclically refreshed display device which generates a plurality of writing strokes for each display line, information characters being displayed by selectively changing the visible state of M bits of each of N strokes for each character, incorporates means for causing the display to travel in fractional stroke increments, comprising: counters 40 and 38, each unit increment of which corresponds respectively to a predetermined fractional stroke increment and to a full stroke increment of the display, means 72-90 for determining the number of predetermined fractional stroke increments by which the display is to be incremented, means 92 responsive to this number for incrementing counter 40 thereby, and means 106-150, 62, 60 responsive to the counter outputs for controlling both the stroke and the bit thereof at which display of the first of a series of characters begins. The present invention is a modification of the C.R.T. display of Specification 1,395,922 which displays alphabetic stock 10 codes and numeric prices in matrix form on staggered lines L2, L3 (Fig. 3A). Display data 18 is input to a memory 10 via a buffer 20, a detector 22 incrementing a counter 16 and a detector 34 adding an extra 0 or 1 bit according as the data is for line L2 or L3. During read-out under control of counter 12, this bit is detected at 44 and gate 52 or 68 is enabled at L2 or L3 time accordingly, the data passing to a generator 58 and a display 63. Circuitry 72-78 determines how many stored characters have still to be displayed, which number provides an output 94 from a circuit 92. The fraction of a stroke is one-third of a stroke (3 bits) here: the corresponding output 94 (e.g. 94A=3 bits) causes counter 40 to be incremented, counter 38 being incremented if there is an overflow therefrom. At the end of a line, one of gates 106 is enabled (depending on the output of counter 38) at the corresponding stroke in the next character time; the output from the gates is fed to a flip-flop 142 and a 6-character delay 146. A clocking input to flip-flop 142 and a flip-flop 62 is obtained from one of gates 136 at a bit time corresponding to the count in 40. The set output from 142 triggers the line retrace operation in the display; at the same time flip-flop 62 is reset to disable gate 60 to prevent display during line retrace. After 6 character times, delay 146 applies a set input to flip-flop 62, which is clocked by the output from 136, thus enabling gate 60 again. The net result of this is that the first strokes and/or bits of the first word are not displayed, and the corresponding portions of the next new word are displayed at the end of the line, the minimum portion being 3-bits (onethird stroke). A similar operation takes place for a non- travelling display, using gates 130, 134 enabled during bit 1 of stroke 1.