US Patent 7596770 Temporal decomposition for design and verification

Behavior of a finite state machine is represented by unfolding a transition relation that represents combinational logic behavior of the finite state machine into a sequence of transition relations representing combinational logic behavior of the finite state machine in a sequence of time frames. At least one state is determined in a transition relation in the sequence that cannot be reached in a subsequent transition relation in the sequence. A subsequent transition relation in the sequence in which the at least one state cannot be reached is simplified with respect to the at least one unreachable state.