Patent GB-982677-A (GB)
Title: Improvements in binary information transfer devices
IPC: G11C19/08
Filed: 1961-09-22
Abstract: 982,677. Magnetic logical circuits. INTERNATIONAL BUSINESS MACHINES CORPORATION. Sept. 22, 1961 [Sept. 23, 1960], No. 33963/61. Heading H3B. The stray magnetic fields of a plurality of controlling thin magnetic film elements 11, 12, 13, Fig. la, determines the stable state of an adjacent controlled thin film element 14. The controlling elements 11, 12 have stable states established by input signals, while element 13 is maintained in a selected stable state so as to function as a reference element. All the easy axes are arranged in the same direction 15. For the controlled element to be established in a stable state in accordance with the stray fields, it is first magnetized in the hard direction by energizing a conductive loop 16. When the energization is removed by opening switch 17, Fig. 1b the magnetization of element 14 falls back along the easy axis in a direction determined by the stray fields. As shown, for example, the controlled elements 11, 12 are switched to opposite states by input signals, and since reference element 13 provides a closed flux path with element 12 the controlled element takes up the magnetic state of element 11. With the reference element magnetized to the right as shown, the logical OR operation is performed on inputs to elements 11 and 12. On the other hand the AND operation is carried out if the reference element is magnetized to the left. In a modification, Fig. 3 (not shown), the reference element is replaced by a conductive loop around element 14, and the direction of loop current determines the mode of logical operation. Preferably the loop is pulsed only during the period in which information is to be transferred to the controlled element. In a further embodiment, Fig. 4, the reference element 23 has its easy axis 33 inclined by an angle e of between 5 and 50 degrees with respect to the general easy axis direction 30. This enables the reference element to return to a required stable state following temporary switching to the hard direction by a pulse in a conductor loop 29, this switching operation being necessary so that the controlling elements 21, 22 may take on stable states determined by the stray fields of respective preceding elements 27, 28. Since the direction of restoration of the reference element field depends on the hard axis direction to which it was switched, selection of the logical OR or AND operation depends entirely on the direction of pulse current in loop 29. A logical NOT circuit is shown in Fig. 6 in which the input is applied from element 39 to controlling element 41 by stray field action. The principles of operation are shown in Figs. 8a-8d. Initially controlling elements 42, 43 are switched to opposite directions along the easy axis 40 by current pulses in respective loops 52, 53, and element 41 is switched to the hard direction by a longer pulse in loop 51, Fig. 8a. When the longer pulse terminates, element 41 takes up a magnetic state along the easy axis in accordance with the stray field from element 39, Fig. 8b. Elements 42 and 43 are then switched to the hard direction by a pulse in a common loop 55, Fig. 8c. When this pulse ceases elements 41 and 43 together form a closed magnetic path as shown in Fig. 8d, and since element 42 takes up the same state along the easy axis as element 43, the resulting stray field is in the opposite sense to that which acted from element 39 to element 41. A logical AND or OR circuit combining the outputs of thin magnetic film shift registers 60, 80 as described in Specification 912,314 is shown in Figs. 9a-9f. As described in the prior Specification, each register comprises magnetic elements arranged in staggered formation in three planes A, B and C. The registers 60 and 80 have their final elements 70, 90 arranged in planes C and A respectively, Figs. 9a and 9b, and the reference element 75, Fig. 9d, is positioned in plane B. When assembled as shown in Figs. 9e and 9f, the elements 70, 90 and 75 interleave, the shift registers 60, 80 being mutually positioned at an angle of 45 degrees with respect to the reference element assembly 120 and an outgoing shift register 100. As the shift registers have a 90 degrees angle between them, the stray field from each final element 70, 90 cannot influence the other. The final elements are shaped as shown in Fig. 9f so that all the elements 70, 75, 90 have an edge 71, 76, 91 parallel with the edge 109 of the first element of shift register 100. The final elements are also thicker by a factor of #2 than the reference element so that equal stray field components are produced along the easy axis which lies in the plane of register 100. Information is shifted along the registers in the manner described in Specification 912,314, the conductor loops in planes A, B and C of registers 60 and 80 being pulsed in accordance with the pattens in Fig. 10a and 10b respectively. As each pulse in a plane terminates, the elements in that plane are switched into a stable state in the easy direction according to the stray field direction of the adjacent elements in an unenergized plane. Thus at time positions t 6  and t 10 , information is read into final elements 70 and 90 respectively (pulse patterns 60-C and 80-A in Figs. 10a and 10b). At time t 13  the cross field energization of element 110 in shift register 100 terminates as shown in Fig. 10c at 100-B, and the element takes up a magnetic state along the easy axis as determined by the stray fields of final elements 70 and 90 and the reference element. Spurious operation at other times is prevented by pulsing conductor loop 77 of the reference element as shown in Fig. 10d and by a step-wise reversal of the pulses in planes A and C of registers 60 and 80 respectively. The first element 110 of the register 100 is zeroed between times t 3  and t 5  by a strong pulse applied to a conductor loop 106, Fig. 10e. In a modification, Fig. 11, the conductor loop 106 is also pulsed between times t 12  and t 14  and functions in place of the reference element assembly 120. If this additional pulse REF is positive the circuit performs the logical AND operation, and if negative the OR operation. Constructional details are as described in Specification 912,314.