Patent GB-1061485-A (GB)
IPC: G11C11/20
Filed: 1964-08-04
Abstract: 1,061,485. Circuits employing bi-stable magnetic elements; parametrically excited resonators. INTERNATIONAL BUSINESS MACHINES CORPORATION. Aug. 4, 1964 [July 25, 1963], No. 30673/64. Heading H3B. [Also in Division H1] In digital data storage apparatus comprising a plurality of bi-stable magnetic elements first and second alternating magnetic fields and a steady magnetic field are applied to each element, the fields being such that when the alternating fields are in phase their joint effect on the state of the element is determined by the polarity of the steady field, whilst when the alternating fields are out of phase the state of the element is unaffected. In the matrix of Fig. 1 each core N is threaded by a column wire 2 and write and read wires 23, 24 respectively. To write a word into a selected column a composite A.C. and negative D.C. signal is supplied from mixer 4 through selector 7 to the appropriate column winding 2 and an A.C. of the same frequency and of predetermined phase relationship determined by the value of the bit to be inserted is applied to each row. The two A.C. signals are in phase for writing " 1 " and 180 degrees out of phase for binary " 0." As indicated in Fig. 2 (not shown) in an unselected core, the A.C. information field, curve (C1), is' insufficient to switch the cores, all the cores being initially in a positive state of saturation. In a selected core receiving a binary " 0 " information signal on its row winding 23 the alternating fields cancel out and the steady field (C2) is insufficient to switch the core, leaving it in its state of positive saturation, binary " 0." If the information signal is in phase with the A.C. signal on the column winding, binary " 1," curve (C3), the core is progressively switched to negative saturation. In order to read out an A.C. of frequency equal to that of the signal applied to winding 23 together with a positive D.C. signal are applied to the column winding selected so as to restore any switched core to positive saturation and induce an A.C. signal of fixed phase in sense wire 24 connected to parametron 10. The parametron, Fig. 3, has one input connected to the sense winding 9 of an auxiliary core 8 connected as shown, the windings of which are such that during write operations the core is negatively saturated and during read out is positively saturated, and the oscillations on winding 9 are in phase opposition to those on sense wire 4. The amplitude of the signal on wire 4 is arranged to be twice the amplitude of that of winding 9 and so that the phase of the current in primary winding 10f and hence of output winding 10h will be determined by the E.M.F. on wire 4. A binary " 1 " is indicated by an output at 10h of the same phase as that of the A.C. applied to the core and a binary " 0 " by an output signal in phase opposition, in this case no signal is induced in sense wire 4. Series read and write is performed using the arrangement of Fig. 4 (not shown) in which an information wire (11) and sense wire (12) thread all the cores of the matrix and each core is threaded by two selector wires (13), (14). In order to write in a digit a D.C. is applied to the appropriate row winding and an A.C. of the same frequency as the information signal on winding (11) is applied to the appropriate column winding. A selected core is subjected to a steady field if a binary " 0 " is written in since the phase of the information signal on (11) is 180 degrees out of phase with the column select wire so that no switching of the core takes place. Similarly, if a binary " 1 " is written in the phases of the A.C. signals are the same and the core is switched to negative saturation, Fig. 5 (not shown). In order to read out the D.C. is reversed and an A.C. of greater amplitude than in the writing operation is applied to the column selector winding. Signals induced in the sense winding (12) are applied to a parametron (15). Reference has been directed by the Comptroller to Specification 822,212.