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Considering process variability at the behavior synthesis level is necessary, because it makes some instances of function units slower and others faster, resulting in unbalanced control steps and reducing the attainable frequency of the circuit. To tackle this problem, this paper proposes a methodology to replace the edge-trigged flip-flops by transparent latches, to exploit latches' extra ability of passing time slacks and tolerating delay variations. In the paper we first define the timing yield in high-level synthesis, and then present how to replace flip-flops with latches to improve timing yield and mitigate the impact of process variations. We then discuss the benefits and overheads for the replacement, and propose an optimization framework for latch replacement in high-level synthesis design flow. Experimental results show that the latch-based design can achieve an average of 27% improvement of timing yield compared with traditional flip-flop based design.
Date of Conference: 19-22 Jan. 2009