Patent GB-1528949-A (GB)
Title: Memory device
IPC: G11C11/14
Filed: 1975-10-28
Abstract: 1528949 Magnetic storage arrangements PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 28 Oct 1975 [31 Oct 1974] 44361/75 Heading H3B The route taken by a magnetic bubble in a storage system is determined and a positional delay relative to other bubbles is obtained by controlled reversals of a bubble-propagating, in-plane, rotating magnetic field, each reversal extending over a predetermined integral number of one quarter cycle periods. A storage system is shown in Fig. 1 and comprises a propagation line extending between a bubble generator 1 and a bubble annihilator 8, with diverging switches 2, 4 ... 14 and converging switches 3, 5 ... 13 coupling the line with storage loops 15, 16, 17. Outputs for reading by a detector 24 are obtained from the loops by way of bubble splitters 18, 19, 20, output structures 26, 27, 28 and read coders 21, 22, 23, the latter preventing bubbles in parallel from arriving simultaneously at the detector. Bubble delay for use in the coders may be obtained by the scalene parallelogram element 72 in the T and I bar bubble propagation overlay pattern 70-76 shown in Fig. 2. In the element 72 bubbles propagated through the pattern from left to right by an anticlockwise (positive) rotating field pass through positions 1, 2, 3 between bars 71 and 73. If the direction of the field is reversed (negative) the bubble at bar 73 passes through positions 3, 2, 1 in element 72 and then circulates clockwise by way of positions 4, 3, 2 etc. On restoring the rotating field to the clockwise sense the bubble proceeds normally from the element towards bars 73, 74, 75, 76. Since any reverse direction bubble is trapped by element 72 its relative position in a pattern of propagated bubbles is changed, the positional variation being determined by the number of negative one quarter cycle periods. In a modification, Fig. 3 (not shown) a scalene parallelogram element is a mirror image of element 72, in which case a bubble is trapped when propagated from left to right by a positive rotating field. Fig. 4 shows an alternative delay arrangement in an overlay pattern 90-99. A positive rotating magnetic field propagates a magnetic bubble along the line of elements 90-96. If however a bubble is positioned at element 95 and the field direction is reversed, the bubble moves backwards and diverts to positions 3 and 2 of element 95. By changing the field back to the positive direction the position 2 on element 93 is reached. A further reversal and restoration of the field direction then moves the bubble into the line of elements 90-97 to continue its propagation. Propagation in the reverse direction along the line is possible. A modified arrangement is described, Fig. 5 (not shown) which operates in a similar manner but is suitable for left to right bubble propagation only. The delay elements and structures described may be used to provide a staggered delay for parallel bubbles proceeding to a common detector 218, Fig. 3, each delay being represented by a rectangle. Various coded arrangements are described, Figs. 6 to 9 (not shown). The details of the storage system of Fig. 1 are shown in Fig. 10, in which an overlay pattern defines a propagation line 400-409, unitary diverging and converging switches 463-466 and 467-470 for storage loops 410-416 and 417-423, and bubble splitters 479. In each case where a bubble is to be diverted, converged or split the rotating magnetic field is reversed a predetermined number of times in each of a given integral number of one quarter cycle periods.