Methodology and tools for state encoding in asynchronous circuit synthesis

This paper proposes a state encoding method for asynchronous circuits based on the theory of regions. A region in a Transition System is a set of states that “behave uniformly” with respect to a given transition (value change of an observable signal), and is analogue to a place in a Petri net. Regions are tightly connected with a set of properties that must be preserved across the state encoding process, namely: (1) trace equivalence between the original and the encoded specification, and (2) implementability as a speed-independent circuit. We build on a theoretical body of work that has shown the significance of regions for such property-preserving transformations, and describe a set of algorithms aimed at efficiently solving the encoding problem. The algorithms have been implemented in a software tool called petrify. Unlike many existing tools, petrify represents the encoded specification as an STG, and thus allows the designer to be more closely involved in the synthesis process. The efficiency of the method is demonstrated on a number of “difficult” examples