Patent GB-1334663-A (GB)
Title: Data stores
IPC: G11C19/08
Filed: 1972-02-11
Abstract: 1334663 Magnetic storage arrangements INTERNATIONAL BUSINESS MACHINES CORP 11 Feb 1972 [22 March 1971] 6413/72 Heading H3B [Also in Division G4] A shift register uses cylindrical magnetic domains which are circulated in one direction or the other according to the direction of rotation of an in-plane magnetic field, the domains in one direction of movement only being available for deflection into an access position for reading or writing. Two groups d, a, Fig. 5, of such registers each containing page bits I to K form data and access registers, the registers operating on the basis that bits K initially in the access positions form the page last addressed, the next available bits K-I form the page penultimately addressed and so on. The data registers d are written into or read out over AND gates A-2, A-3 in conjunction with a write control applied to each access position, operation of the AND gates being conditional on an address match in the access registers signalled over line 104. The access positions of the address registers a are coupled to an address comparison unit ACU which signals "match" on line 104 or "no match" in response to an address applied over lines 118 from a using unit to a memory address register MAR. An address mismatch operates a no match latch NML which locks the comparison unit into a search condition and at the same time opens AND gate A-4. A shift control unit is then operative over line 138 to effect left shift in the registers, the page bits K moving along loop L1 from the access positions to the initial positions of page bits 1 and their place being taken by K-1. This movement is repeated for K-1, K-2 &c., until a match is obtained, when a signal on line 104 applied through an inverter closes gate A-4 to terminate leftward shift. Each left shift is counted up by a two-way counter 200, and when a match is obtained a right shift is commenced through AND gate A-5 until the counter is counted down to zero. Gate A-6 then opens and turns off latch NML, removal of the latch signal from line 104 causing a hold condition to be established through an inverter 144. The right shift operation in the registers takes place over shortened loop L2, and at the time the counter 200 reaches zero and the hold condition operative the previous first page bits K are in the position K1 shown, and so on. A single register is shown in Fig. 3 and comprises a domainsupporting platelet 210 subjected to an orthogonal bias field and having an overlay pattern of T and I permalloy bars. An in-plane rotating magnetic field 211 causes a domain pattern to propagate along a closed path 228 with each domain representing a binary "1". Anticlockwise rotation of the magnetic field causes a clockwise domain propagation 232 corresponding to leftward shifting, while the reverse direction of magnetic field causes anticlockwise domain propagation 244 corresponding to rightward shifting. The closed path 228 corresponds to loop L2, while this closed path together with an access position 215 for reading or writing corresponds to loop L1. Control and reading of the propagated domains is effected by printed conductors 217, 224, 240 and 244. During clockwise propagation a domain is moved into the access position by energizing shift control conductor 240, and the domain is read out by a magneto-resistive element 225 connected to bit sense conductor 224. A domain is destroyed by energizing conductor 244 and a new domain generated in an elongate bar 212 is introduced by energizing a write control conductor 217. When rightward shifting takes place the anticlockwise moving domains are unable to enter the access position, and any domain located in that position is held there by following a circulating path 246 between the ends of bars 216, 218, 222 and 248.