GB1024025A - Digital comparison member - Google Patents

Abstract

1,024,025. Digital comparators. LICENTIA PATENT-VERWALTUNGS-G.m.b.H. April 22, 1964 [April 22, 1963 (2)], No. 16662/64. Heading G4M. In an arrangement for comparing for equality and for relative magnitude two multi-digit numbers, the digits of the numbers are arranged in groups, each group corresponding to digits of the same orders in each number, each group receiving inputs from the respective digits of the two numbers to be compared and providing output signals, the output signals for the various groups being combined in a further logical output circuit to produce the required comparison signals. The switching time required to effect a comparison is thus reduced. The switching circuits described comprise diode AND and OR gates and are interconnected by inverter gates comprising transistors, a single transistor being indicated in the figures by a thick black bar and two such transistors in series by a black- and-white bar, the interconnections being such that AND and OR gates are controlled only by stages employing transistors. The Specification describes numerous arrangements for comparing two multi-digit numbers a, b, having binary digits ai, bi, a relation a > b being indicated by P = 1, a < b by N = 1 and a = b by K = 1, with corresponding relations for the individual digits ai, bi and indicators Pi, Ni, Ki. The equality relationship of a group of digits, e.g. digits of orders 3, 4 and 5 is indicated by symbols such as P 5/3 , N 5/3 , K 5/3 , which are = 1 according as the numbers a 5 a 4 a 3 , b 5 b 4 b 3 are in the relationship >, <, =. In the circuit shown in Fig. 9 for comparing two 12-digit binary numbers, the digits are arranged in four groups, with three digits in each group, the groups thus corresponding to digit positions 2-0, 5-3, 8-6 and 11-9 respectively, switching circuits S 45 -S 52 providing, for each of the four groups K- and P-type (as defined above) output signals such as K 2/0 and P 2/0 , these signals being applied to further switching circuits S 53 -S 55 which produce the desired output signals P 11/0 , N 11/0 , K 11/0 (and their inverses). In other circuits (Figs. 10-12, not shown) the grouping of the digits and/or the particular auxiliary signals K, P or N developed by the groups differ from the arrangement of Fig. 9 and in further modifications (Figs. 13- 19, not shown) different arrangements are illustrated for forming the final outpur signals from the intermediate signals such as K 2/0 , P 2/0 .