Signal Transition Graph Constraints for Synthesis of Hazard-Free Asynchronous Circuits with Unbounded-Gate Delays

A synthesis procedure for asynchronous control circuits from a high level speci cation signal transition graph STG is described In this paper we propose some syntactic constraints on STG to guarantee hazard free im plementation We have introduced a global persistency concept in order to establish the relationship between the persistency concept introduced by Chu which we call local persistency and the consistent state coding CSC The STG syntactic constraints required to compute the input set of a signal are identi ed We analyze all hazards under both single and multiple input change conditions and propose necessary changes to the net contraction and logic synthesis procedures The proposed changes are guaranteed to generate hazard free circuits with the unbounded gate delay model if the STG is live safe and has consistent state coding