On hazard-free implementation of speed-independent circuits

Abstract

We investigate the problem of hazard free gate level implementation of speed independent circuits specified by event based models, such as signal transition Graph (for processes with AND causality and input choice) or its extension, called change diagram (which allows OR causality). The main result of the paper is twofold: the proof that any speed independent behavior can be implemented at the gate level without hazards; and an efficient method for such an implementation. This method is based on transformations of the specification to the form satisfying the monotonous cover requirement. Since this method is based on standard gate cells it can be used both in the full custom and semi custom VLSI design. Experimental results demonstrate area and performance efficiency of our method.