Patent GB-1125099-A (GB)
Title: Arrangement for minimizing noise in a plated wire memory
IPC: G11C11/14
Filed: 1966-11-15
Abstract: 1,125,099. Circuits employing bistable magnetic elements. SPERRY RAND CORP. 15 Nov., 1966 [19 Nov., 1965], No. 51096/66. Heading H3B. In order to minimise noise during a read cycle the plated wire storage elements are divided into two symmetrical groups each group including a dummy wire element and all the elements of each group being connected to respective terminals of a differential amplifier. The arrangement shown comprises a plurality of wires plated with magnetic material and divided into two groups 13, 15 17 and 13<SP>1</SP>, 15<SP>1</SP>, 17<SP>1</SP>. Included in each group is a wire 19, 19<SP>1</SP> which is not plated and all the elements of group 10<SP>1</SP> are connected to terminal 32 of differential amplifier 70 and of group 10<SP>11</SP> to terminal 34. During read out of information stored in a particular plated wire a signal is applied to word conductor 51 and the switch S.W. of the selected plated wire is energized together with the switch S.W. of the dummy wire 19, or 19<SP>1</SP> in the other group to that of the selected wire. In addition to the signal induced in the plated wire a noise signal is produced primarily due to the energizing of the word line 51 by capacitive coupling and in addition to the word line noise there is noise which passes through the unselected matrix switches S.W. due to the junction capacitances of the transistors of the switches and also capacitance coupling of word line noise through the unselected matrix switches. The noise which passes through the unselected switches in the upper section 10<SP>1</SP> is substantially the same as that in the lower section and due to the symmetrical arrangement of the elements connected to the diffential amplifier the noise at the terminals 32, 34 cancels out. The amplifier is arranged so that the signal at terminal 34 is subtracted from terminal 32 and the signal at output terminal 70 is indicative of the binary digit stored. Since a binary "1" will have different polarity signals at the output of the amplifier depending on whether it is read in the upper section 10<SP>1</SP> or the lower section 10<SP>11</SP> the bit driver arrangement shown is used. In order to write information in a word current is passed to word line 51 and a bit current is simultaneously passed through a selected plated wire. In order to overcome the polarity problem the same'binary information is recorded by using opposite steering or bit currents in the upper and lower portions 10<SP>1</SP>, 10<SP>11</SP> and the binary value chosen is determined by which switch S1, S2 is closed. Closing one of the switches S1, S2 of the bit driver S2 causes a positive current to flow in the upper section 10<SP>1</SP> and a negative current to flow in the lower section. Closing the other switch causes a negative current to flow in the upper section and a positive current in the lower. Thus during writing the appropriate switch S1, S2 is closed and the switches S.W. of the selected plated wire and the dummy wire in the other group of the matrix are placed in their low impedance conditions. This results in a digit being stored in the plated wire which will produce at the output 70 a signal of the same polarity regardless of whether the plated wire is in the upper or lower section. The opposite polarity signal representing the other binary value is produced when the other one of the switches S1, S2 is closed and the other binary digit is stored.