Patent GB-1432454-A (GB)
Title: Magnetic shift register store
IPC: G11C11/14
Filed: 1973-08-30
Abstract: 1432454 Magnetic storage arrangements PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 30 Aug 1973 [2 Sept 1972] 40833/73 Heading H3B In a moving magnetic bubble domain arrangement, Fig. 5, in which domains 5 representing "0" and "1" bits are respectively propagated along two adjacent paths 2, 3, the paths are arranged sufficiently close with respect to the bubble diameter that a bubble in one path prevents, by magnetic interaction, a bubble in the other path from overtaking in the direction of domain propagation. The propagation paths may be formed by spaced strips of soft magnetic material on a plate of anisotropic magnetic material capable of supporting bubble domains, or may be formed by parallel grooves or scratches on the plate, each groove or scratch separating one propagation path from the other. In a further construction, Fig. 4 (not shown), two propagation paths are obtained by providing a single strip of permanently magnetized material on the plate, one propagation path being obtained along each edge of the strip. In the arrangement shown in Fig. 5, domains from a generator 9 are projected along a single path 8 to a branch point 12, where bubbles representing a "0" bit are diverted to an upper path 2 while bubbles representing a "1" bit are diverted to a lower path 3. Separation of the "0" and "1" domains is effected by the direction of current in a loop 11 coupled to patl 2. Magneto resistive detectors 13<SP>1</SP>, 14<SP>1</SP> are provided in the two paths for read out, the read out signal passing to an OR gate 15. Synchroniz ation between input and output is obtained by a feedback circuit including an OR gate 16. In a modification, Fig. 6, a continuously circulating bubble system is obtained by recombining the two paths at the readout point and providing a feedback path 20 between outlet and inlet. Bubble transport is effected by alternating current from a source 21 in loops 8. A wire loop bubble detector 23 controlling a multivibrator 24 is used for read out, the multivibrator switching each time a successive bubble is detected in a different path. A further arrangement, Fig. 7, has the two propagation paths 2, 3 terminated by a curved link 26 extending between magnetoresistive detectors 13<SP>1</SP>, 14<SP>1</SP>. In this arrangement a domain in one path will proceed directly along the loop unless the next domain in the series is in the other path. Thus a binary "0" bubble 27 detected by 13<SP>1</SP> denotes that the next bubble 28 in a series 27, 28, 29, 30 is a binary "1". Detector 14<SP>1</SP> will not become operative until reached by bubble 29, denoting that the next bubble 30 represents a binary "0". Each detected bubble is destroyed by a current pulse applied to a terminal 31. Bubble propagation in one direction may be aided by the provision of outwardly tapered paths, Fig. 8 (not shown). A pattern of "1" and "0" bit bubbles 37 in a first magnetic plate 33, Fig. 9, may control the movement of additional information bubbles 39, e.g. representing word endings, in a propagation path 38 in an adjacent second plate 34, the path 38 being spatially positioned between the first plate paths 35, 36.