Patent GB-783391-A (GB)
Title: Improvements in or relating to digital data-storage systems
Filed: 1955-12-08
Abstract: 783,391. Electric digitaldata-storageapparatus. COX, B., and GOLDBERG, J. Dec. 8, 1955 [Jan. 10, 1955], No. 35314/55. Class 106 (1). Apparatus for transferring data from a first tape to a second tape comprises means to transfer data in an ordered sequence from the first tape to a plurality of registers, means to transfer data in an ordered sequence from the registers to the second tape, means to prevent transfer into a register when data is being transferred out of the register, and means to prevent transfer out of a register when data is being transferred into the register. As described, three shifting registers RA, RB, RC, Fig. 1, are provided, each capable of storing a word. The first data word read from the first tape and arriving on a common input channel A, is fed into the register RA, the second word into RB and the third word into RC. Control of the gating arrangements for this sequence is exercised by a first three-stage counter, Fig. 2, having outputs 1, 2 and 3 operative only when the corresponding stage is operative, and outputs 1, 2 and 3 operative when the corresponding stage is not operative. A second counter, Fig. 3, similarly arranged, its three stages referenced 11, 12 and 13, controls the reading out of words from the three registers RA, RB and RC in succession via a common channel B to the writing head of the second tape. The means to prevent read-in and read-out from one register occurring simultaneously include groups of AND gates similar to that shown in Fig. 4. Operation. A master start pulse is developed in a generator 35, Figs. 1, 2 and 3, e.g. upon pressing a " start " button. This sets both counters to the first stage and sets a flip-flop 32 which transmits a signal to each AND gate 26A, 26B, 260. The signal C = 1 from the first counter opens the AND gate 26A and allows a signal to pass via OR gate 24A to the shift pulse generator 20A which, receiving clock pulses a from a generator 22, steps the shift register RA along to receive the first word. When an " end of word " signal is received by a device 84, Fig. 2, it steps the first counter to stage two thus transferring the input from the tape to feed the second word into the register RB. Similarly the next " end of word " signal steps the counter to stage three and the C = 3 input at AND gate 260 allows the third word to pass into the register RC. Transfer of data from the registers to the second tape is initiated when the first counter steps to stage two. Signals C = 11 and C = T open AND gate 102, Fig. 4, and, via OR gate 100, render operative a word pulse generator 112. A signal from the generator 112 passes via a " word start " device 60, and AND gate 56 to set a flip-flop 54. This provides an input signal to AND gates 48A, 48B and 480 and, since the first of these receives both C = 1 and C = 11, the shift pulse generator 20A is again brought into operation to feed out the registered word through AND gate 130 to the writing head. When the end of the word is reached a signal appears in a device 62, Figs. 1 and 3, which steps the second counter to stage 12, and resets the flip-flop 54. Normally, the second shift pulse generator 20B will be started by a further reversal of the flip-flop 54 and the coincidence of signals C = 12 and C = 2 at AND gate 48B. Read-in and read-out from the registers RA, RB and RC continues in this way unless read-in tends to " overtake " read-out. If the entry of a word into a register is completed before read-out from the next succeeding register, one of the AND gates 120, 122, 124 responds, causing the setting of a flip-flop 110. This causes the following sequence to occur under the control-it is suggestedof a fourstage ring counter: the first tape is stopped and marked, driven in reverse for a suitable distance, wiping off any previous marks which may be encountered, then driven forward again. By the time the interruption mark is reached the delay in read-out will, normally, have been cleared and a signal from a device 44 that the first tape is running forward, together with a signal from the mark detector 46 at AND gate 42, causes a resumption of the read-in process. The setting of flip-flop 110 also provides an input (= 1) at OR gate 100, Fig. 4, which maintains operation of the word pulse generator 112 for read-out to the second tape, but when both counters reach similar stages one of the AND gates 140, 142, 144 responds and resets the flip-flop 110, restoring control of read-out to normal.