Patent GB-1286393-A (GB)
Title: Improved apparatus for displaying and editing information
Inventor: THOMPSON GLEN RUTHERFORD
IPC: G09G1/22
Filed: 1970-04-20
Abstract: 1286393 CRT displays A C COSSOR Ltd 19 April 1971 [20 April 1970] 18789/70 Heading H4T In apparatus for displaying and editing information, binary coded characters are stored in a circulating store synchronous with a major raster scan on a display tube, and are successively presented to a symbol generator responsive to each code to provide a corresponding video signal synchronous with a minor raster, scanned by the display tube at each character position traversed by the major raster; such video signals being applied to the display tube to cause successive characters stored in groups to be repeatedly delineated on the display screen as plurallines of characters, with each group corresponding to a specific line and the groups being separated by gaps of the store corresponding to line and frame flyback intervals of the major raster; the apparatus also comprising means for checking the first and last groups in the store during every recirculation, operative to transmit the first group to a unit receiving information from the display apparatus whenever the first group is full of characters and also to automatically fill the last group from the unit supplying the information when such last group contains no characters. A CRT 10 (Fig. 1) displays 540 characters in a frame of 54 Î 10 (+1 flyback line) with 10 character flyback intervals under control of crystal oscillator 12 (Fig. 2) subdivided by 8 to produce clock pulses CK and phase pulses PH1 to PH4 timing logic sequences in each clock period. Further subdivision by 7 produces character pulses CH and bit mark pulses BT1 to BT7, by 64 produces line pulses LN, and by 11 produces frame pulse FR. The states of the dividers 18 and 20 are coded to identify first and last characters FC, LC and line blanking interval LB, and also to provide line markers LL1 to LL11, and the waveforms are illustrated (Fig. 5, not shown). A precisely timed recirculating store 22 comprises a wire delay line 24 followed by a 7 bit shift register 26 in loop with normally open gates 28, 30, of which the latter is closed during line and frame flybacks by LB, LL11, so that the recirculating data comprises 10 spaced groups of 54-7 bit characters each corresponding to a display line, which successively shift through 26. When the 7 bits of a character load the register, they are transferred to staticizer 32 driving vertical and horizontal circuits 34, 36 deflecting the beam of monoscope 38 to the position of a predetermined character; V and H time bases being superimposed from 42, 40 triggered by pulse CH to develop a minor scanning raster, and the corresponding signal being gated at 46 to modulate display tube 10 whose beam is deflected by H and V time bases 48, 50 triggered by pulses LN, FR to describe a major 10 line raster, on which at each character position a minor raster is superimposed by combination of the output of 42 with that of 50. Data is   entered to store 22 by keyboard 52 and store 53 which is coupled to shift register 26 and also from input register 56 buffering a tape reader, computer, or other source over gate 54; while readout data is gated over 60 to output register 58. As data is fed in, it moves progressively up the display screen and on insertion the preceding data is progressed upscreen and out of store, and as new characters are keyed in one by one the preceding characters regress through the lines, so that at the beginning of the line of insertion the characters concerned and lines above them are impelled into the ends of the preceding lines i.e. each character is regressed 11 positions in the store. For control, (Fig. 6) flip-flop 62 is reset by each line pulse LN and is set by any data pulse DD at input of shift register 26; the changeover signalling by NE that the line is not empty. NE is gated by LL10 and LN to control flip-flop 64 to generate signal RX when the last line is empty, so as to demand data from a source, which enters a data line character by character, and then signals LS to reset flip-flop 64. Signal NE is also gated by LL 1, FC to indicate presence of a character in the first position of the first line, to set flip-flop 66 signalling TX to open gate 60, which instructs the output unit 58 to receive a data line; after which signal LR resets flip-flop 66. Thus when line 10 empties it is automatically filled from the source, while when the line fills it is automatically emptied. Flipflop 68 is set by NE gated with LL1 to signal by CL the presence of a character in the first line; at the end of which it is reset by LN. Operation of key 69 sets flip-flop 70 to impose a step on signal SP, which is gated with CL (if present) to set flip-flop 66 for transmission of any characters in the first line, and [SP+CL] sets flip-flop 72 to signal by SR an upward shift of one line, by reason of the insertion of a line period delay before the next frame pulse; SR being gated by LL11 to close gate 84 (Fig. 2) to suppress one line pulse from the counter. Gating of SR with LL11 and LH resets flip-flops 20, 72. A circuit 86 (Fig. 1) responds to CR synchronous with VTB 42 to bright up a cursor display bar under a selected monoscope character to indicate a point for correction, insertion, or deletion. Signal CR is generated (Fig. 7, not shown) in response to operator keys denoting LEFT, RIGHT, UP, DOWN for moving the cursor, which add or subtract a digit from corresponding cyclic counters respectively clocked through codes of 54 and 10 states by character pulses CH in presence of LB, and LN in presence of LL11; specific states being decoded to outputs CP and CS marking the position in a line and a line itself of the cursor, while a gate responds to CP, CS jointly to give CR, which transfers the contents of store 53 (representing a replacement character) from key board 52 (Fig. 1) into shift register 26 to erase and replace the character therein. For insertion and deletion, a delete key (or a character key and an insert key) sets sequential flip-flop and gate logic (Fig. 8, not shown) responsive to signals CR, FR to generate a signal SO closing gate 28 to delete a character from register 26, and advances subsequent characters one gate via by-pass gate 102 and registers 106, 108, or to advance the characters one place and insert a character on store 53 into the register 26 to fill the gap; in response to signal CR. Eight typeface codes represented by boxed symbols 1 to 8 of the monoscope select type faces and are assigned to four type combinations e.g. ROMAN, ROMAN ITALIC, BOLD, BOLD ITALIC by patchboard 138 whose output 140 denotes italic and outputs 142, 144 denote roman and bold; the former being light on dark by opening gate 46 to allow video to energize the display, and the latter being dark on light by opening gate 146 for energization through an inverter. Italic is displayed by opening gate 150 to skew the raster by subtracting part of the VTB signal from the HTB signal. A non-displayed cursor denotes a character in the first or last line which is being transmitted or received; a cyclic counter 152 (Fig. 6) and decoder 154 (responsive to RX and TX designating character position 1 on the rising edge of either signal, and the character TX or RX) sends signal NC calling for the next character, thereby adding 1 to counter 152. The resultant signal DP is gated with LL1 and TX to produce DT for gate 60 (Fig. 1) to open and is also gated with LL10 and RX to produce DR for gate 54 to open. Bits are clocked out of and into registers 56, 58 while monoscope 38 and display 10 are blanked in known manner. The first and last lines of characters are blanked to avoid confusion due to the automatic shifts.