NOVA: state assignment of finite-state machines for optimal two-level logic implementations

The problem of encoding the states of a synchronous Finite State Machine (FSM), so that the area of a two-level implementation of the combinational logic is minimized, is addressed. As in previous approaches, the problem is reduced to the solution of the combinatorial optimization problems defined by the translation of the cover obtained by a multiple-valued logic minimization or by a symbolic minimization into a compatible Boolean representation. In this paper we present algorithms for their solution, based on a new theoretical framework that offers advantages over previous approaches to develop effective heuristics. The algorithms are part of NOVA, a program for optimal encoding of control logic. Final areas averaging 20% less than other state assignment programs and 30% less than the best random solutions have been obtained. Literal counts averaging 30% less than the best random solutions have been obtained.