Patent GB-926016-A (GB)
Title: Information transfer superconductor circuit
IPC: G11C19/32
Filed: 1959-09-22
Abstract: 926,016. Superconductive circuits. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 22, 1959 [Dec. 22, 1958], No. 32284/59. Class 40 (9). [Also in Group XIX] A data-stepping circuit which may be used as a stepping register, a counter or a parallel-toserial converter, employs cryotrons and each stage of the circuit comprises a cryotron flipflop controlling the conductivity of a pair of output lines on one of which the stepping pulse appears to set the flip-flop of the next stage, gate conductors associated with the output lines having control coils wound in such manner that the transferring flip-flop is not affected by the state of the preceding flip-flop until the stepping pulse is removed. The flip-flop of stage B consists of two conductive paths extending between terminals 14B and 15B across which a potential difference always exists: the path 10B, which is superconductive to represent 0, comprising coils 17B and 20B, cryotron gate 24B and coil 26B; and the path 12B, which is superconductive to represent 1, comprising cryotron gate 18B and coils 30B, 34B and 36B. The flip-flop is set by external signals to coils 40B or 44B, or by signals controlled by the state of the flip-flop of the preceding stage to coils 42B or 46B. The cross-coupling coils 17B, 34B ensure the stability of the current paths. The state of the flip-flop is exhibited by one of the conductors 28B, 38B being resistive. From terminal 54B to which the stepping pulse is applied two paths extend: 56B which includes gate conductor 32B, self-biasing coil 60B and coil 46C on the gate conductor 18C; and 58B which includes gate conductor 22B, self-biasing coil 62B and coil 42C on gate conductor 24C. The coils, e.g. 30B and 60B, are wound on gate conductor 32B in opposition and the stepping pulse is of such magnitude that a current through coil 60B alone is not sufficient to send conductor 32B resistive, but is such that if both coils are energized the effect of coil 32B is nullified. Assume that stage A contains 0, stage B, 1. Initially line 56A is superconductive, and in stage B current flows in path 12B through coil 30B to render conductor 32B resistive, leaving path 58B superconductive. The transfer pulse is applied at terminals 52A, 52B and in stage B takes path 58B to energize coil 42C to set the flip-flop to 1. Stage A conducts the stepping pulse through coil 46B rendering path 12B resistive and causing energization of coil 20B in path 10B. The effect of the coil 20B is nullified by the action of self-biasing coil 62B through which the stepping pulse is passing, so that conductor 22B remains superconductive until the pulse ceases when stage B will assume the state 0 with conductor 22b resistive. Although both conductors 22B and 32B are superconductive at some time there will be no tendency for the already flowing current in superconductive path 58B to take path 56B. Since the counter wound coils on conductors 22B and 32B are coupled and both conductors are superconductive there is a tendency that current in paths 56B, 58B which form a closed loop may persist. This may be obviated by connecting another coil in each of the paths 10B, 58B, 12B or 56B, coupling the coils in associated paths in a sense opposite to the coupling of coils 30B and 60B, 20B and 62B. A closed ring counter may be constructed by connecting the paths 58C, 56C to coils 46A, 42A, respectively, and an open ring counter by connecting path 58A to coil 46A instead of to ground. This connection may be used in a parallel-to-serial converter to clear the register as the word is stepped out. Read-out of the register after each stepping pulse without destroying the contents is obtained by connecting the paths, e.g. 56A, 58A to binary one or zero output connections, instead of to ground. Persistent current cryotrons may be used instead of the gates described. Specifications 862,178, 887,112, 887,113, 887,654 and 926,015 are referred to.