NETWORK HIERARCHIES AND NODE MINIMIZATION

Over the last decade, research in the automatic synthesis and optimiza tion of combinational logic has matured significantly; more recently, research has focused on sequential logic. Many of the paradigms for co mbinational logic have been extended and applied in the sequential dom ain. In addition, promising new directions for future research are bei ng explored. In this paper, we survey some of the results of combinati onal synthesis and some recent results for sequential synthesis and th en use these to view possible avenues for future sequential synthesis research. In particular we look at two related questions: deriving a s et of permissible behaviors and using a minimizer to select the best b ehavior according to some optimization criteria. We examine these two issues in increasingly complex situations starting with a single-outpu t function, and proceeding to a single multiple-output function, a net work of single-output functions, a network of multiple-output function s, and then similar questions where ''function'' is replaced by a fini te state machine (FSM). We end with a discussion of a network of finit e state machines and the problem of deriving the set of permissible FS M's and choosing a representative minimum one.