Patent GB-1134474-A (GB)
Title: Magnetic core memory
IPC: G11C11/06
Filed: 1967-04-28
Abstract: 1,134,474. Circuits employing bi-stable magnetic elements. INTERNATIONAL STANDARD ELECTRIC CORP. 28 April, 1967 [3 May, 1966], No. 19774/67. Addition to 1,071,998. Heading H3B. In a magnetic storage arrangement as described in the parent Specification in which a preparatory pulse switches all the cores to the " 1 " state before writing and reading pulses, all of the same " 0 " driving polarity, are applied in turn, a half-current disturb pulse is additionally applied immediately following each of the pulses. Each disturb pulse is of opposite polarity to the pulse immediately preceding, and to avoid the use of bipolar inhibit drivers only the write disturb and read disturb pulses are passed through the inhibit line as shown in Fig. 5. To write a " 0 " in the store at a selected location, half-current " 0 " switching pulses W are coincidently applied to X and Y lines, followed by a write disturb pulse Z 0  in the inhibit line. No separate disturb pulse is necessary when core switching is prevented by a half current inhibit pulse Z 1  to enable a " 1 " to be stored. Following reading by applying coincident read pulses R of the same polarity as the write pulses to switch " 1 " state cores to the " 0 " state, a disturb pulse is applied to the inhibit line. The disturb pulse following the preparatory pulse is applied either to all the X lines or all the Y lines, Fig. 6, and is of the same polarity as a read or write pulse. Each of the X (or Y) lines is disturbed in turn, and for this reason the disturb pulse is made up of a series of pulses Y 1 -Y m , one for each line. A suitable control circuit is shown in Fig. 7 in which ZX and ZY are counters controlling electronic switches SX1-SXn, SY1-SYn in the X and Y drive lines respectively, Fig. 1 (not shown), and DL is a delay line from which the various pulse timings are determined. In response to a reading or writing instruction BR or BW and the presence of a clock pulse CL, gates O1, U1 are opened and a pulse passed down the delay line. Between tappings 1 and 4 on the delay line, and during the writing phase, gate U2 is opened and applies an inhibition criterion to inhibition drivers (TZ1, TZ2 . . . ), these drivers in conjunction with information criteria (INF1, INF2. . . ) determining the binary value to be written. At tapping 3 an instruction PWD is produced which causes the inhibition drivers to apply the short duration write disturb pulse. Between tappings 2 and 3 gate U3 is opened and causes the X and Y over BTX, BTY to transmit X and Y drive pulses. For reading the same sequence takes place except that gate U2 remains closed and no inhibition criterion is produced. For producing the preparation pulse, the inhibit drivers receive an instruction (I) to generate a full current inhibit pulse. The subsequent disturb pulses are produced in response to an instruction BP which transmits a pulse down the delay line and disables gate U4 and the X drive circuit. When the pulse reaches tapping S the counter ZY is stepped once. Repeated disturb pulses Y 1 -Ym are generated by passing repeated pulses along the delay line, the counter being stepped to a further Y line each time. At the end of the count a signal C through gate U6 indicates termination E.