GB1207032A - Feed control system - Google Patents

Abstract

1,207,032. Selective signalling. R.C.A. CORPORATION. 24 May, 1968 [29 June, 1967], No. 24835/68. Heading G4H. A printer, Fig. 1, in which the paper feed is controlled by one of a plurality of programmes punched in a photo-electrically read tape loop 58, is characterized in that a plurality (eight) of rows of the loop are recorded in image form in a high speed store, whereby when paper feeding has to take place the control circuit can " look ahead " and if the paper has to be moved a sufficient number of lines (e.g. more than nine lines) the drive can be at high speed reverting to low speed just before the desired position is reached. Each track on the programme loop of tape, Fig. 2, relates to a different programme, and the holes are punched in row positions corresponding to lines on the paper in which printing is to occur. Thus, in the example shown, programme No. 4 will cause the paper to stop at lines N+2, and N+3. In prior arrangements, the position of the programme loop read station corresponds to the line of paper under the print hammer-the " print line "- and paper feeding continued until a hole was sensed in the operative programme. In the present arrangement, the programme loop read station is positioned eight rows in advance of the print line, and an image of the intervening eight rows of the programme loop is retained in a high speed core store arranged so that the eight bits relating to any one of the twelve programmes on the programme loop can be addressed by a single number. For example, as shown, address 84 in the store corresponds to programme No. 4 on the loop. As the rows on the programme loop are successively read, when paper feed is occurring, the data in the core store is successively shifted to the right so that nine rows. of the programme loop (the one currently being read, and the eight in the core store) are always available fcr use in determining the speed of paper feeding. The control circuit for updating the core store as successive rows of the programme loop are read is shown in Fig. 3. When a row is read 62, Fig. 3, it is entered into a buffer 102 under the control of clock-pulses derived from a photo-electrically sensed disc 42, Figs. 1, 3. Under the control of relatively high frequency clock-pulses 110, Fig. 3, the eight bits (plus possibly a ninth parity bit) in address position 81 of the core store 100 are read into a shift register 172. This register is then shifted to the right taking in one bit from the buffer 102 at the left and losing one bit at the right. The result is then read back to the main core store 100 and updating of address No. 81 is complete. A similar operation is performed for the remaining eleven addresses in the store 100. Control of paper feed speed is effected by logic 174, Fig. 3 (Fig. 4, not shown), which, when that row of the main store 100 that corresponds to the particular programme exercising control has been transferred to the shift register, has available to it nine bits of the programme from which the appropriate speed can be determined.