Patent Publication Number: US-RE29677-E

Title: Single-wall domain arrangement

Description:
FIELD OF THE INVENTION 
     This invention relates to data processing arrangements and more particularly to such arangements in which information is represented as single-wall domains. 
     BACKGROUND OF THE INVENTION 
     The term &#34;single-wall domain&#34; refers to a magnetic domain which is movable in a layer of a suitable magnetic material and is encompassed by a single domain wall which closes on itself in the plane of that layer. 
     Propagation arrangements for moving a domain are designed to produce magnetic fields of a geometry determined by the layer in which a domain is moved. Most materials in which single-wall domains are moved are characterized by a preferred magnetization direction, for all practical pruposes, normal to the plane of the layer. The domain accordingly constitutes a reverse magnetized domain which may be thought of as a dipole oriented transverse, nominally normal to the plane of the layer. Accordingly, the movement of a domain is accomplished by the provision of an attracting magnetic field normal to the layer and at a localized position offset from the position occupied by the domain. A succession of such fields causes successive movement of a domain in a selected direction. 
     One particularly attractive arrangement for providing the propagation fields is disclosed in A. H. Bobeck U.S. Pat. No. 3,534,347, issued Oct. 13, 1970. That patent describes a pattern of magnetically soft elements coupled to the layer in which domains move. The elements are of a geometry and so disposed to exhibit changing magnetic pole patterns in response to a magnetic field reorienting, typically rotating, in the plane of the layer. Domains follow the changing pole pattern from input to output positions thus realizing shift register operation in response only to the in-plane field--an operation termed &#34;field access.&#34; 
     U.S. Pat. No. 3,618,054, issued Nov. 2, 1971 of P. I. Bonyhard, U. F. Gianola and A. J. Perneski discloses an organization of a domain, field-access arrangement in what is called a &#34;major-minor&#34; mass memory. Magnetically soft elements are arranged to define a plurality of closed &#34;minor loops&#34; which recirculate domain patterns in response to the in-plane field. The minor loops come in close proximity to a &#34;major loop&#34; arranged perpendicular to the axes of the minor loops. Information is transferred between the minor loops and the major loop at transfer positions defined where the loops are most closely spaced. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention relates to an arrangement for moving domains between first and second propagation paths or loops at such a transfer loop. The transfer loop is defined by magnetically soft elements to have first and second domain paths which terminate at each end at a common element. Movement of domains is in a first or second direction in the first or second path, respectively, in response to a first orientation sequence, illustratively clockwise rotation, of the in-plane field depending at which common element to the domain enters the transfer loop. Entrance of a domain at the first or second common element of the loop depends on timely pulses in conductors positioned to displace a domain moving at least partially thereunder. A domain moving in a channel from which transfer is to occur is displaced, by the field generated by the pulse, to a pole in the associated common element alternative to that to which the domain would normally move next when the in-plane field reorients. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a line diagram of a single-wall domain memory including a transfer region in accordance with this invention; 
     FIGS. 2 through 7 are schematic representations of portions of the transfer region of FIG. 1; and 
     FIGS. 8 an 9 are schematic representations of alternative transfer regions for the memory of FIG. 1. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a single-wall domain memory organization 10 comprising a layer of material 11 in which single-wall domains can be moved. Domains are moved in layer 11 along channels defined by elements of magnetically soft material, typically deposited by photolithographic techniques as an overlay on a suitable spacing layer (not shown) on the surface of layer 11. The elements are of geometries and so disposed with respect to one another to exhibit moving pole patterns in response to a rotating inplane magnetic field to propagate domains in parallel in closed minor loops organized in right and left sets as represented by the oval-shaped loops designated merely L1 - LN for convenience. 
     The overlay elements also define a single major loop shown as a vertically oriented oval-shaped loop LM in FIG. 1. As is well known, information is recirculated in the minor loops for transfer of selected date (a bit from each minor loop) to the major loop where the data is advanced to a read-write position designated by double-headed arrow RW in FIG. 1. The selected data, illustratively, is returned thereafter to associated vacancies created in the minor loops by the initial transfer. The data in the major loop as well as in the minor loops is moved responsive to the in-plane field rotations and thus is synchronized by that field so that selected data is returned to the original positions in minor loops simply by the occurrence of a data return transfer operation at the appropriate number of field rotations after an initial data transfer operation. 
     An input pulse source represented by block 12 in FIG. 1 and a utilization circuit represented by block 13 are coupled to a read-write position for operation as described in the above-mentioned patent of P. I. Bonyhard et al. An in-plane field source is represented by block 14 in FIG. 1. In practice, a magnetic bias field represented by block 15 in FIG. 1 maintains domains in layer 11 at a specified diameter as is well known. 
     Sources 12, 14, and 15, and circuit 13 are connected to a control circuit represented by block 16 in FIG. 1 for synchronization and activation. The various sources and circuits may be any such elements capable of operating in accordance with this invention. 
     The transfer of information (data) in major-minor arrangements occurs at transfer positions defined by magnetically soft elements in the region where each minor loop is most closely spaced from an associated stage of the major loop. A representative transfer region is located at 19 in FIG. 1 and shown in detail in FIG. 2. The elements 20 form part of the major loop LM which is indicated by the broken closed arrow so designated in FIG. 2. The element 21 forms a part of the representative minor loop L2 which is indicated by the broken arrow so designated. A transfer position in accordance with this invention comprises a loop which includes these loop-defining elements plus the remaining elements therebetween as shown in FIG. 2. 
     The remaining elements can be seen to be generally of Y and bar-shaped geometries. The Y-shaped elements 22 and 23 are most closely associated at their basis with loops LM and L2 respectively and actually define domain positions in those channels. The Y-shaped elements also are noted to be positioned in a mirror image arrangement about bar-shaped elements 24 and 25 spaced apart along a vertical axis 26 as shown in FIG. 2. 
     Electrical conductors 28 and 29 couple layer 11 of FIG. 1 along the positions also coupled by the Y-shaped elements 22 and 23, respectively, for all the transfer positions to at least one side and typically both sides of the major loop. Conductors 28 and 29 are connected to a transfer pulse source 30 as shown in FIGS. 1 and 2. 
     The transfer loop defined by elements 22, 23, 24, and 25 will now be shown operative responsive to a pulse on conductor 28 to transfer a domain from the major loop into minor loop L2 within two propagation cycles (viz: two rotations of the in-plane field). The loop will also be shown operative in response to a pulse on conductor 29 to move a domain from minor loop L2 into the major loop within two propagation cycles. 
     Consider a domain moving clockwise about loop LM in FIG. 2 and arriving at position 31 of an element 20 associated with the representative transfer loop as shown in FIGS. 2 and 3. The in-plane field is directed upward at this juncture as indicated by the arrow H in FIG. 2. The inplane field next reorients to the right as indicated by the arrow H in FIG. 3. The domain, in response, moves to position 33 at the base of Y-shaped element 22 shown in FIG. 3. The next normal position for a domain moving in loop LM would be position 34 in FIG. 3 attained when the in-plane field reorients to a downward direction. However, here pulse source 30 applies a pulse to conductor 28 while the domain is in position 33. The pulse generates a field which moves the domain to position 35 of FIG. 4. Thus, when the in-plane field next reorients to a downward direction as shown by arrow H in FIG. 4, the domain moves to position 36 there instead of position 34. 
     Clockwise rotation of the in-plane field through one and a half cycles of operation commencing with the movement of a domain to position 33 moves the domain further into the succession of positions 37, 38, 39, 40, and 41 as shown in FIG. 5. At this juncture, transfer pulse source 30 of FIGS. 1 and 2 illustratively applies a pulse to conductor 29 for moving the domain from position 41 to a position 42 in FIG. 6. 
     Rotation of the in-plane field to an upward direction as indicated by the arrow H in FIG. 6 results in the movement of the domain to position 44. The domain is now positioned for movement into the succession of positions 45, 46, 47, etc., in minor loop L2 for clockwise movement thereabout in response to subsequent cycles of the in-plane field. 
     The illustrative transfer of a domain from major loop LM to a representative minor loop L2 has now been shown. 
     The transfer of a domain from the representative minor loop to the major loop is entirely analogous to the above transfer operation illustratively employing a pulse in each of two conductors one and a half cycles of the in-plane field apart. In this instance also, the in-plane field rotates in the clockwise direction described but the transferred domain moves about the upper leg of the transfer loop of FIG. 2 rather than the lower leg as described above. 
     FIG. 7 identifies a position 50 which a domain occupies during normal movement clockwise in loop L2. When the in-plane field next reorients to a leftward direction as indicated by arrow H in FIG. 7, the domain moves to position 51 at the base of Y-shaped element 23. 
     At this juncture, transfer pulse source 30 applies a pulse to conductor 29 resulting in the movement of the domain to position 52. When the field next reorients to an upward direction, the domain moves to position 53 rather than to a next normal position 54. The next one and a half cycles of the in-plane field moves the domain through the succession of positions 54, 55, 56, 57, and 58 as shown in FIG. 5. 
     Source 30 applies a pulse to conductor 28, at this juncture, resulting in the movement of the domain to position 33 of FIG. 3 for movement to position 34 in FIG. 3 when the in-plane field next reorients downward. Note that the polarity of the pulses in conductors 29 and 28 for movement of a domain from the minor loop to the major loop is opposite to those applied for movement of the domain in the opposite direction. Source 30 is considered to include circuitry operative in a suitable manner. 
     The transfer of a domain from a representative minor loop to the major loop has now been shown. It should be remembered, however, that conductors 28 and 29 couple all the transfer loops of FIG. 1. Since the in-plane field synchronizes domain movement in all the major and minor loops, the pulsing of those conductors results in the simultaneous movement of all domains occupying domain positions at transfer loops when a transfer pulse occurs. Thus, a bit from each minor loop is transferred to an associated stage of the major loop. An absence of a domain in any of those domain positions is, of course, similarly &#34;transferred.&#34; Thus, a domain pattern representative of a binary word is transferred during the transfer operation leaving &#34;bit&#34; vacancies in each minor loop for synchronous movement by the in-plane field. 
     A binary word is similarly transferred from the major loop. But due to the geometrical requirements of the elements and the spacing between minor loops, adjacent positions 33 are spaced two stages apart as is clear from FIG. 2. Thus, only every other stage of the major loop is occupied in the illustrative embodiment as is consistent with prior art thinking. 
     The illustrative arrangement employs a sequence of two pulses to achieve the transfer operation. On the other hand, only one conductor need be pulsed to move a domain into the transfer position for automatic egress when the inplane field moves the domain to the opposite &#34;entrance-exit&#34; position (viz: positions 33 and 51 of FIGS. 3 and 7). This is clear from FIG. 7 where it may be appreciated that a domain would &#34;prefer&#34; to occupy position 51 rather than position 52. In this mode of operation a transfer conductor is pulsed for gating a domain into a transfer loop at one of two entrance-exit positions therein for movement along an upper or lower leg of the transfer loop for automatic egress at the other of the two entrance-exit positions. 
     This &#34;single pulse&#34; transfer operation can be enhanced by modifications in the geometry of the pattern of magnetically soft elements. FIG. 8, for example, shows an alternative pattern for defining a transfer loop. 
     To be specific, FIG. 8 shows an alternative pattern of magnetically soft elements for defining a transfer loop between elements 20 of major loop LM and element 21 of minor loop L2. The Y-shaped elements 22 and 23 and elements 24 and 25 of FIG. 2 are seen to have their counterparts in this embodiment leading to an operation analogous to that already described. 
     On the other hand, additional elements 60, 61, 62, and 63 are shown in FIG. 8. These elements are operative to provide an intermediate position 64 between positions 33 and 34, for example, when the in-plane field reorients from a rightward direction to a downward direction as is the case when exit from the transfer loop to the major loop occurs. The existence of the intermediate position ensures the exit of the domain with relatively high operating margins. Conductors 28 and 29 are pulsed for transfer from the major to the minor loops and for transfer from the minor loops to the major loops, respectively, in the manner described above. 
     FIG. 9 shows a pattern of elements which define a transfer loop requiring fewer than two cycles for a complete transfer. A domain in this embodiment moves from position 35 to position 41 in one half cycle of the in-plane field rotation. Both conductors are pulsed herein as in the embodiment described in connection with FIGS. 2 through 7. 
     Like designations are used for like elements in the various embodiments to emphasize the similarity therebetween. 
     What has been described herein is considered merely illustrative of the principles of this invention. Therefore, various modifications can be devised by those skilled in the art in accordance with those principles within the spirt and scope of this invention. For example, the number of cycles required for traversing the transfer positions may be varied as well as the number of pulses as is clear from the described embodiments.