Patent GB-1207082-A (GB)
Title: Dummy wire selection scheme for data processing equipment memory system
IPC: G11C7/02
Filed: 1969-01-23
Abstract: 1,207,082. Data storage. SPERRY RAND CORP. 23 Jan., 1969 [30 Jan., 1968], No. 3736/69. Addition to 1,125,099. Heading G4C. [Also in Division H3] In a plated wire store in which the plated wires A1-A16, Fig. 1, are divided into two groups A1-A8 and A9-A16 each with a respective non-magnetic dummy wire D1, D2, and in which for noise suppression during read out a differential sense amplifier 16 is connected to a selected plated wire and a dummy wire by switches 20-29, the same dummy wire is selected for a read out operation as was used in the write or read operation immediately rreceding if the two address words are the same, and the other dummy wire is sleeted if the address words differ. The store includes a word drive selector 44, a bit driver 12, an active wire selector 14 which selects a single plated wire A1-A16 by applying an inhibiting " 1 " output to all but one of the switches coupled to plated wires, and a dummy wire selector 10 also applying an inhibiting " 1 " output to one or other of the dummy wire switches 22, 27. The dummy wire selector is shown in detail in Fig. 2, and includes a present address register 50, a prior address register 52, and a comparator 54 for comparing the prior and present addresses, each device receiving the present address 2‹, 21, 2<SP>2</SP>, 2<SP>3</SP> and its complement #2‹, #2<SP>1</SP>, #2<SP>2</SP>, #2<SP>3</SP>. The present and prior registers are gated in time positions T1 and T2 respectively, and the comparator provides an output on one or more leads 130-136 to trigger a read/enable gate 56 during a read operation if one or more of the compared digits differ. A bi-stable dummy wire selector 58 applies a " 1 " output to each of the two dummy wire switches 22, 27 in turn over leads 62, 64, and is connected to a toggle 60 which operates to reverse activation of one of two input leads 90, 91 of the dummy wire selector if the selector output is changed over. The dummy wire selector is also controlled by the comparator output through the read/enable gate during a read operation as well as by the highest order address digit 2<SP>3</SP> and its complement #2<SP>3</SP>. Consequently, if the read address corresponds to the prior address, no output is obtained from the read/enable gate and the highest order digit is the same. The toggle input is then unable to influence the dummy line selector and the same dummy wire switch is operative as before. If the read address differs from the prior address the read/enable gate causes the output to the dummy wire switches to be reversed. The direct application of the highest order digit and its complement causes a changeover in output to the dummy wire switches at all times if the present and prior highest order digits are different, all addresses with a " 0 " highest order digit being applied to the plated wire group A1-A8 and those with a " 1 " being applied to the group A9-A16. Consequently a dummy wire becomes operative during writing operations in the other store group to that which corresponds to the write address. The plated wire conductors may be enfolded by the ground plane.