Patent GB-755441-A (GB)
Title: Binary-decimal adder
IPC: G06F7/495
Filed: 1954-02-17
Abstract: 755,441. Digital electric calculating-apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Feb. 17, 1954 [Feb. 20, 1953], No. 4649/54. Class 106 (1). An electronic adding device for binary-coded decimal digits supplied successively, comprises groups of input terminals each for receiving simultaneously binary bits representing one of the decimal digits, a binary adder for each binary order connected to add the associated bits, carry terminals from the adders connected to inputs of the next higher adders, the carry terminal for the highest order adder being connected to the lowest order adder through a connection including a one-decimal-digit delay circuit, and a rationalizer connected to receive the sum output of each binary adder, except the lowest, and the carry output of the highest adder, the rationalizer comprising OR and AND circuits connected to provide an output indicating a sum greater than 9, and pulse transfer and coincidence circuits connected to be energized by this latter output and the output of preselected ones of the binary adders to add 6 to the sum. In the binarydecimal adder shown, each decimal digit is represented by potentials (high for " 1 ", low for " 0 ") applied simultaneously to four lines representing binary values or " bits " 1, 2, 4, 8. The decimal numbers to be added are applied digit by digit to input terminals 11, 12 and the different bits are applied to separate binary adders 15 having sum and carry outputs 15-1, 2, 4, 8 and 16-1, 2, 4, 8 respectively. The outputs 15-2, 15-4, 15-8, 16-8 are connected to the inputs of the " rationalizer " or coding arrangement 19, the decimal sum digit being represented by the potentials on output terminal 15-1, and rationalizer output terminals 20-2, 21-4, 22-8. The decimal carry digit appearing on output terminal 23-10 is delayed one digit period in circuit 25 and applied to the carry input 17 of the " 1 bit " binary adder 15 simultaneously with the application of the bits of the decimal digits in the next higher denomination to terminals 11, 12. Circuit diagrams of the delay circuit and binary adders are given. Rationalizer. This may comprise " AND " and " OR " gates and inverters " INV " (or " not devices) connected as shown in Fig. 6 between the input terminals 15-2, 15-4, 15-8, 16-8 and output terminals 20-2, 21-4, 22-8, 23-10. The numbers in the rectangles indicate the decimal sum values for which a corresponding line is at high potential. For example, the potential at output 23-10 is high for values 10 to 19 for which either the potential at input 16-8 is high (representing a carry from " 8 bit " adder 15, Fig. 1) or a high potential at input 15-8 (representing 8) is accompanied by a high potential at 15-4 or 15-2 (representing 4 or 2). An OR gate 172 therefore connects 15-2 and 15-4 to AND gate 171a to which 15-8 is also connected, and the output of this AND gate and input terminal 16-8 are connected via OR gate 170 to line 173 and terminal 23-10. Line 173 is connected through inverter 177 to junction point 178 which is therefore high for values 0 to 9. This point and terminal 15-8 are connected to AND gate 195a whose output line 196 is therefore high for values 8 and 9 only. The terminals 16-8 and 15-2 are connected to AND gate 197a whose output line 198 is high for values 18 and 19. The lines 196 and 198 are connected through OR gate to terminal 22-8. The required outputs at terminals 21-4 and 20-2 are similarly obtained. A circuit diagram is given (Fig. 6a, not shown) in which the inverters are triode circuits, the AND gates are diode networks and the OR gates are diode networks or cathode follower circuits. Other forms of rationalizer comprising different arrangements of gates and inverters are described and shown.