Latency Optimized Asynchronous Early Output Ripple Carry Adder Based on Delay-insensitive Dual-rail Data Encoding

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aut.relation.endpage74
aut.relation.journalINTERNATIONAL JOURNAL OF CIRCUITS, SYSTEMS AND SIGNAL PROCESSINGen_NZ
aut.relation.pages10
aut.relation.startpage65
aut.relation.volume11en_NZ
aut.researcherPrasad, Krishnamachar
dc.contributor.authorBalasubramanian, Pen_NZ
dc.contributor.authorPrasad, Ken_NZ
dc.date.accessioned2019-02-17T22:58:39Z
dc.date.available2019-02-17T22:58:39Z
dc.date.copyright2017-06-14en_NZ
dc.date.issued2017-06-14en_NZ
dc.description.abstractAsynchronous circuits employing delay-insensitive codes for data representation i.e. encoding and following a 4-phase return-to-zero protocol for handshaking are generally robust. Depending upon whether a single delay-insensitive code or multiple delay-insensitive code(s) are used for data encoding, the encoding scheme is called homogeneous or heterogeneous delay-insensitive data encoding. This article proposes a new latency optimized early output asynchronous ripple carry adder (RCA) that utilizes single-bit asynchronous full adders (SAFAs) and dual-bit asynchronous full adders (DAFAs) which incorporate redundant logic and are based on the delay-insensitive dual-rail code i.e. homogeneous data encoding, and follow a 4-phase return-to-zero handshaking. Amongst various RCA, carry lookahead adder (CLA), and carry select adder (CSLA) designs, which are based on homogeneous or heterogeneous delayinsensitive data encodings which correspond to the weak-indication or the early output timing model, the proposed early output asynchronous RCA that incorporates SAFAs and DAFAs with redundant logic is found to result in reduced latency for a dualoperand addition operation. In particular, for a 32-bit asynchronous RCA, utilizing 15 stages of DAFAs and 2 stages of SAFAs leads to reduced latency. The theoretical worst-case latencies of the different asynchronous adders were calculated by taking into account the typical gate delays of a 32/28nm CMOS digital cell library, and a comparison is made with their practical worst-case latencies estimated. The theoretical and practical worst-case latencies show a close correlation. The proposed early output 32-bit asynchronous RCA, which contains 2 stages of SAFAs in the least significant positions and 15 stages of DAFAs in the more significant positions, reports the following optimizations in latency over its architectural counterparts for a similar adder size: i) 35.3% reduction in latency over a weakindication section-carry based CLA (SCBCLA), ii) 30.5% reduction in latency over a weak-indication hybrid SCBCLA-RCA, iii) 20.2% reduction in latency over an early output recursive CLA (RCLA), iv) 18.7% reduction in latency over an early output hybrid RCLA-RCA, and v) a 13% reduction in latency over an early output CSLA that features an optimum 8-8-8-8 uniform input partition.
dc.identifier.citationInternational Journal of Circuits, Systems and Signal Processing, Vol. 11, pp. 65-74.
dc.identifier.urihttps://hdl.handle.net/10292/12252
dc.publisherNorth Atlantic University Union (NAUN)
dc.relation.urihttp://www.naun.org/main/NAUN/circuitssystemssignal/2017/a162005-aaz.pdfen_NZ
dc.rightsThe PDF files of all NAUN Journals are open to everyone, without any username/password requirements.
dc.rights.accessrightsOpenAccessen_NZ
dc.subjectAsynchronous design; Digital circuits; Single-bit full adder; Dual-bit full adder; Ripple carry adder; Indication; Early output; Standard cells; CMOS
dc.titleLatency Optimized Asynchronous Early Output Ripple Carry Adder Based on Delay-insensitive Dual-rail Data Encodingen_NZ
dc.typeJournal Article
pubs.elements-id281541
pubs.organisational-data/AUT
pubs.organisational-data/AUT/Design & Creative Technologies
pubs.organisational-data/AUT/Design & Creative Technologies/Engineering, Computer & Mathematical Sciences
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