Patent GB-977986-A (GB)
Title: Improvements in magnetic memory elements and matrices
Inventor: HARMAN MICHAEL GODFREY
IPC: G11C7/00
Filed: 1962-01-09
Abstract: 977, 986. Digital data storage. NATIONAL CASH REGISTER CO. Jan. 8,1963 [Jan. 9, 1962], No. 746/62. Heading G4C. [Also in Divisions H1 and H3] A magnetic storage element comprises a storage flux path and a plurality of independent write legs coupled thereto, each write leg including an enabling winding and a write winding, the flux in the storage path being switched to a direction dependent on the polarity of the write winding current applied to a single write leg when the write winding and the enabling winding are energized simultaneously. The element may also have a plurality of independent read means, and when used in a matrix which may be a control circuit for a computer different word lines may be switched at the same time. Basic arrangements using bias. A storage element is shown in Fig. 1 in which a core of material having a rectangular hysteresis characteristic is formed with a single write leg 1, two storage legs 7 and 8 which together provide a storage flux path 6, and independent read out apertures 9, 10 and 11. The write leg only is shown in Figs. 1A to 1F and is provided with a continuously energized bias winding B, a write winding W and an enable winding E. The bias current establishes fluxes about write leg apertures 4 and 5 as shown in Figs. 1A and 1B, and when the bias is neutralised by simultaneously energizing the enable and write windings a flux which traverses the storage path is produced as shown in Figs. 1C and 1D, the flux direction being determined by the write winding polarity. When the enable and write winding energizations terminate the storage path flux is modified by the bias as shown in Figs. 1E and IF, the flux then passing in opposite directions through the respective storage legs 7 and 8. The storage flux path is further modified whenever read out takes place by energizing a read winding R1 to R3, Fig. 2, each read out operation inducing an output in the associated sense winding S1 to S3. The read out operation is possible only once for each read out aperture provided since a localised flux is produced about the interrogated aperture; however the equivalent storage condition may be reestablished when required by pulsing a restore winding Q. In a modification, Fig. 3, the restore winding is normally energized and produces a clockwise flux in that part of the legs 7 and 8 between the read out apertures and the central opening. The flux in the outer part of the legs 7 and 8 has a direction determined by the writing operation. To read out, the winding Q is de-energized, a read winding (only R1 is shown) is pulsed, and winding Q subsequently reenergized. A further modification is shown in Fig. 4 in which each read location comprises radial apertures 12, 13, 14, reading being effected by overcoming a permanent read bias in winding RR by pulsing a read enable winding RE and a read winding R simultaneously. In Fig. 5 independent read out apertures 19, 20 are arranged radially and each aperture has its own read and sense windings R1, S1. To avoid spurious outputs all the read windings should be energized simultaneously. Provision of several write legs. The write legs of Fig. 1 may be repeated in a series formation with the extremities connected to the storage legs 7, 8. Several enabling windings may be provided either on respective write legs or on a single write leg so that simultaneous energization is necessary to overcome the bias. Alternatively as shown in Fig. 6, the separate write legs 1a, 1b may be connected in parallel or may be connected to a different part of the storage flux path as in the case of write leg 1c. Basic arrangement without bias. A storage element comprises a write leg 39, Figs. 9A to 9F, and a read leg, Fig. 10. Four write leg apertures 40-43 are provided which are threaded by an enable winding E and separate windings W 0  and W 1  for writing binary zero and binary one respectively. The write leg forms part of the storage flux path as shown in Figs. 9C to 9F. The enable and one of the two write windings are energized simultaneously to store a binary digit. The flux produced by the enable winding above is shown in Fig. 9B, and the storage flux distribution which is produced by and remains after the enable and write energizations occur simultaneously is shown in Figs. 9C and 9D for binary zero and binary one respectively. Figs. 9E and 9F show that the direction of the storage flux in the vertical legs 37 is unaffected by subsequent pulsing of winding W 0  and W 1  when a binary one or binary zero is stored, respectively. Reading is effected by applying a read enable pulse to winding RE, Fig. 10, to neutralise a permanent read bias in winding RB at the same time as a read winding S is energized. Matrix assembly. Biased elements 29, 30... are used, each having two write legs 1a, 1b, Fig. 7 and a single read aperture 31. Threaded through the various apertures are two separate enable and write windings Ea, Eb and Wa, Wb, bias windings B, and two separate read and sense windings Ra, Rb and Sa, Sb. A row of elements may be formed from a single strip of ferrite, and the read and enable windings may be formed by a printing technique. The storage path of an element is indicated by the broken line 6, and the arrangement operates in the manner previously described. The matrix assembly is shown in Fig. 8, and comprises strips 34, 35, 36... of the elements shown in Fig. 7. The read and enable windings of each strip are connected to respective read and enable drivers RDa, RDb and EDa, EDb, and the write and sense windings are threaded through aligned strip apertures and connected to respective write drivers and sense amplifiers WDa, WDb and SAa, SAb. Thus a binary word can be written into one strip by energizing, for example, an enable driver EDa and appropriately energizing write drivers WDa, and at the same time a word can be written into another strip by energizing an enable driver EDb in coincidence with appropriate energization of drivers WDb. To read two strips simultaneously the respective read drivers RDa and RDb are energized and provide parallel outputs at the appropriate sense amplifiers SAa and SAb. The same word may also be read simultaneously by both sense amplifiers by energizing both the read drivers of a strip.