Irredundant sequential machines via optimal logic synthesis

It is shown that optimal sequential logic synthesis can produce irredundant, fully testable finite-state machines. Synthesizing a sequential circuit from a state transition graph description involves the steps of state minimization, state assignment, and logic optimization. Previous approaches to producing fully and easily testable sequential circuits have involved the use of extra logic and constraints on state assignments and logic optimization. Here it is shown that 100% testability can be ensured without the addition of extra logic and without constraints on the state assignment and logic optimization. Unlike previous synthesis approaches to ensuring fully testable machines, there is no area/performance penalty associated with this approach. This technique can be used in conjunction with previous approaches to ensure that the synthesized machine is easily testable. Given a state-transition-graph specification, a logic-level automaton that is fully testable for all single stuck-at faults in the combinational logic without access to the memory elements is synthesized. >