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Fully Checked Carry Look Ahead Binary Adder

IP.com Disclosure Number: IPCOM000094578D
Original Publication Date: 1965-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Hsieh, P: AUTHOR

Abstract

A carry look-ahead adder can be completely checked by duplicating the sum generation circuits and comparing each duplicated sum with the usual sum.

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Fully Checked Carry Look Ahead Binary Adder

A carry look-ahead adder can be completely checked by duplicating the sum generation circuits and comparing each duplicated sum with the usual sum.

Circuit 10 generates a sum S1 and a function F1 which, when combined in Exclusive Or 12 with carry C2, produces a carry-dependent sum S1'. An article in the IBM Technical Disclosure Bulletin, Vol. 5, No. 7, Dec., 1962, p. 76 describes a carry-dependent sum adder. The carry-dependent sum is compared with the usual sum in Exclusive Or 14. The same functions are repeated for each stage of the adder. The outputs of Exclusive Or's 14, 16, 18, and 20 are combined in Or 22 to provide an error output which detects all single faults occurring in the adder.

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