Logic Synthesis Method for Dual-Rail RSFQ Digital Circuits Using Root-Shared Binary Decision Diagrams

Koji OBATA  Kazuyoshi TAKAGI  Naofumi TAKAGI  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E90-A   No.1   pp.257-266
Publication Date: 2007/01/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e90-a.1.257
Print ISSN: 0916-8508
Type of Manuscript: PAPER
Category: VLSI Design Technology and CAD
Keyword: 
logic synthesis,  dual-rail,  RSFQ,  binary decision diagrams (BDDs),  

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Summary: 
We propose a new method of logic synthesis for dual-rail RSFQ (rapid single-flux-quantum) digital circuits. RSFQ circuit technology is one of the strongest candidates for the next generation technology of digital circuits. For representing logic functions, we use a root-shared binary decision diagram (RSBDD) which is a directed acyclic graph constructed from binary decision diagrams. In the method, first we construct an RSBDD from given logic functions, and then reduce the number of nodes in the constructed RSBDD by variable re-ordering. Finally, we synthesize a dual-rail RSFQ circuit from the reduced RSBDD. We have implemented the method and have synthesized benchmark circuits. We have synthesized dual-rail circuits that consist of about 27% fewer logic elements than those synthesized by a Transduction-based method on average.