Abstract-As process, temperature and voltage variations become significant in deep submicron design, timing closure becomes a critical challenge using synchronous CAD flows. One attractive alternative is to use robust asynchronous circuits which gracefully accommodate timing discrepancies. However, these asynchronous circuits typically suffer from high area and latency overhead. In this paper, an optimization algorithm is presented which reduces the area and delay of these circuits by relaxing their overly-restrictive style. The algorithm was implemented and experiments performed on a subset of MCNC circuits. On average, 49.2% of the gates could be implemented in a relaxed manner, 34.9% area improvement was achieved, and 16.1% delay improvement was achieved using a simple heuristic for targeting the critical path in the circuit. This is the first proposed approach that systematically optimizes asynchronous circuits based on the notion of local relaxation while still preserving the circuit's overall timing-robustness.
In designing asynchronous circuits it is critical to ensure that circuits are free of hazards in the specified set of input transitions. In this paper, two new algorithms are proposed to determine if a combinational circuit is hazard-free without exploring all its gates, thus providing more efficient hazard detection. Experimental results indicate that the best new algorithm on average visits only 20.7% of the original gates, with an average runtime speedup of 1.69 and best speedup of 2.27 (for the largest example).
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