A synthesis for testability scheme for finite state machines using clock control

Abstract—A new method is proposed for improving the testa-bility of a finite state machine (FSM) during its synthesis. The method exploits clock control to enhance the controllability and observability of machine states. With clock control it is possible to add new state transitions during testing. Therefore, it is easier to navigate between states in the resulting test machine. Unlike prior work, where clock control is added to the circuit as a post-design step, here, clock control is considered in conjunction with a symbolic scheme for encoding the states of the FSM. The encoding is shown to result in significant reductions in the interstate distances in the benchmark FSM’s. Further, the observability of the encoded states can be improved by adding two primary outputs to the circuit such that a fixed input sequence forms a distinguishing sequence for all states. Theoretical results show that for a large class of FSM’s, the testability improvements ar