Patent GB-959604-A (GB)
Title: Word selection matrix
IPC: G11C7/02
Filed: 1961-09-29
Abstract: 959,604. Circuits employing bi-stable magnetic elements. SPERRY RAND CORPORATION. Sept. 29, 1961 [Feb. 7, 1961], No. 35346/61. Heading H3B. A magnetic film element 10, Fig. 1, having easy and hard directions of magnetization is biased continuously in the hard direction by current in a transverse bias conductor 12, the magnetization being temporarily switched to the easy direction in one sense or the other by applying a steering pulse of selected polarity to a longitudinal conductor 14, and coincidently neutralizing the hard direction bias by applying a cancelling pulse of shorter duration to the transverse conductor. Magnetic switching to and from the easy direction occurs at the commencement and termination of the shorter cancelling pulse and induces output pulses in a sense conductor 16, at these times. The arrangement may be used in a storage system comprising a selection switch 30, Fig. 3, and a memory array 32, all the switch elements 10<SP>1</SP>-10<SP>N</SP> and memory elements 1 comprising magnetic films. To read out a word stored in the memory, a selected word line is pulsed by temporarily displacing the magnetization of a switching element 10<SP>1</SP>-10<SP>N</SP> to the easy direction so as to induce switching pulses in the associated sense conductor 16<SP>1</SP>-18<SP>N</SP>. This is effected by applying a cancelling pulse to the common bias conductor 12 of the switching elements and at the same time energizing a selected longitudinal conductor 14<SP>1</SP>-14<SP>N</SP> with a steering pulse. As the sense conductors are all terminated by common strips 34, 36, the return current is distributed among the other sense conductors and has no effect on other storage elements. In a modification, Fig. 4 (not shown), each switching element has a separate bias conductor. A storage system comprising three memory planes 36<SP>1</SP>-36<SP>3</SP> and a switching matrix 50 is shown in Fig. 5. The switch elements 50<SP>1</SP>- 50<SP>9</SP> have co-ordinate bias and longitudinal conductors 52<SP>1</SP>-52<SP>3</SP> and 54<SP>1</SP>-54<SP>3</SP>, and to read or write a word in a selected memory plane one each of the co-ordinate conductors is coincidently energized by a cancel and a steering pulse respectively, the polarity of the steering pulse determining the direction of the induced sense pulse. Each memory element in the selected word line, e.g. elements 59, 60, is switched towards the hard direction by the sensing pulse transmitted from the switching matrix, and an output is induced in the associated memory sensing conductor 61 indicative of the remanent directions. To write information into the memory, the input conductors 57 are suitably pulsed while the memory elements are temporarily switched to the hard direction by the sensing pulse from the switch. In order to reduce the bias current, each magnetic film element 70 in the switching matrix may be divided into three segments X, Y, Z, Fig. 7, the bias conductor 72, longitudinal conductor 74 and sensing conductor being arranged as shown. Each film element in the switching matrix may alternatively comprise two films 80, 82, Fig. 8, which are deposited on substates 81, 83 and have the bias longitudinal and sense conductors 84, 86, 88 arranged between them. In a modification the bias conductor may be positioned outside the film pair. Specification 845,604 and U.S.A. Specifications 2,900,282 and 3,026,958 are referred to.