Communications: electrical – Digital comparator systems
Patent
1978-04-17
1979-07-31
Malzahn, David H.
Communications: electrical
Digital comparator systems
364738, 364787, G06F 702, G06F 750, G06F 1110
Patent
active
041632117
ABSTRACT:
A tree-type combinatorial logic circuit comprising a plurality of identical functional units which may be arranged to operate as an N-bit magnitude comparator, a carry generator for an N-bit adder, or a parity predictor for 2N-bit binary counter. Each of the units is provided with four input terminals and two output terminals. The units are arranged to form a binary tree. Each unit has an internal logic circuit which generates outputs of G.sub.K*l =G.sub.K VE.sub.K .multidot.g.sub.l and E.sub.K*l =E.sub.K .multidot.E.sub.l, where "V" and ".multidot." denote Boolean OR and AND operations, respectively. The desired functions are provided at the output terminals of the unit in the final stage of the tree.
The input signals to the units in the first stage of the tree depend on the applications of the circuit. When used as a magnitude comparator, the inputs are a.sub.i .multidot.b.sub.i 's and a.sub.i.sup..sym. b.sub.i 's (i=0, 1,..., N-1), where a.sub.i and b.sub.i are the i-th bits of the two binary words (each N bits long) to be compared, and .sym. represents the Boolean exclusive NOR function. When used as a carry generator, the inputs are a.sub.i .multidot.b.sub.i 's and a.sub.i.sup..sym. b.sub.i 's (i=0, 1, ..., N-1), where a.sub.i and b.sub.i are the i-th bits of two binary words (each N bits long) to be added and .sym. represents the Boolean exclusive OR operation. When used as a parity predicator, the inputs are b.sub.i 's (i=N-1, N-3, N-5, ..., 1 while non-negative) and b.sub.i 's (i=N-2, N-4, ...,) while non-negative, where b.sub.i is the i-th bit of any binary number (N bits long, b.sub.o is the most significant bit) to be incremented by 1 by a binary counter.
REFERENCES:
patent: 3604909 (1971-09-01), Vogel et al.
patent: 3619583 (1971-11-01), Arnold
patent: 3700875 (1972-10-01), Saenger et al.
patent: 3938087 (1976-02-01), Louie
patent: 4084253 (1978-04-01), Miller
Fujitsu Limited
Malzahn David H.
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