Patent GB-1380317-A (GB)
Title: Storage-processor elements
IPC: G06F7/501
Filed: 1972-02-29
Abstract: 1380317 Adder circuits WESTERN ELECTRIC CO Inc 29 Feb 1972 [4 March 1971] 9270/72 Heading G4A [Also in Division H3] A binary store comprises a bi-stable circuit having outputs connected via switches to charge storage devices and means to steer a predetermined current to one or other of two output terminals in response to stored charges. As shown, the output terminals of a bi-stable circuit 21, 22 are connected via normally open diode gates 31, 28 and 32, 29 to charge storage transistors 33, 34 which direct current from the source 38 to terminals 13 or 14. Reading in is. enabled by a source 15 which lowers the potential of terminal 27 and raises the potential of terminal 24. Lowering 27 opens the gate 31, 32 but the output state is retained by the charge storage circuits. Raising 24 switches off both transistors 21, 22 but renders the diodes 18 and 19 conducting so that the state of the input at 11, 12 is applied to the base of terminals of 21, 22. Accordingly when the potential at 24 is lowered again the bi-stable circuit takes up the corresponding state. Reading out is effected by a pulse at 40 which switches off transistor 39 and allows the current from 38 to pass to the appropriate output terminal. Transistors 16- 19 may be replaced by two PNP transistors (Fig. 4, not shown). In Fig. 5 four of the storage elements 61-64 are combined with threshold logic circuits (Fig. 5, not shown) to function as a two-bit adder. Units 63 and 64 receive the binary inputs, unit 62 stores the carry digit and unit 61 provides the sum output on lines 67 and 68, line 69 being a sum signal line and 72 a carry signal line. The bias V R2  on the carry store 62 and the current steering logic circuit 66 are such that with 0 or 1 units of current through resistor 74, elements 62 draws one unit of current and 66 two units of current through resistor 71. Otherwise they draw no current. Bias V R1  applied to store 61 is such that one unit of current is drawn when three units of current pass through resistor 71. Timing pulses are applied by means, not shown, to the storage elements such that while the elements 63 and 64 are receiving data the previous data stored in the charge storage element is being transferred to the sum and carry elements. In Fig. 6 a plurality of the storage elements 81-85 are used in a "twos complement" circuit for words in which the last digit represents the sign. A positive number is passed unchanged but negative number has each digit of the word complemented and a 1 added to the first digit (i.e. the least significant figure). The incoming digits being entered in sequence in true and complement form in storage elements 82 and 83. The circuit also comprises a sign store 84, a carry store 85, an output sum store 81 and a threshold logic circuit 66. The bias suplies V R1  and V R2  are so chosen that the carry store is set only when no units of current are drawn through 88, 81 is set only when one or 0 units of current is drawn through 88 and the threshold circuit provides the output of two units only when two units are drawn through resistor 92. For positive signals the complement store 83 is disabled, the carry circuit is not effective and the output of the sign store is such that the input to store 82 passes unchanged to the output 81. For negative signals the true store 82 is disabled and the complement store 83 is effective to provide the required inversion. For the first bit of the word, a pulse T 0  disables the carry store 85 and enables the sign store 84 whereby a 1 is added to the first digit. For subsequent digits the sign store is disabled and the carry store is enabled. Again, timing pulses, not shown, arrange that while data is being applied to stores 83 and 84 the previous data which is stored in the charge store of the units is being transferred. Modifications of Fig. 6 are described with reference to Figs. 7, 8 and 9 (not shown) and mainly concern the bias and terminals V R1  and V R2  and the inversion of the connections between the storage units and the sum and carry lines.