Synthesis and optimization procedures for fully and easily testable sequential machines

A synthesis procedure is described that produces an optimized fully and easily testable logic implementation of a sequential machine from a state transition graph description of the machine. This logic-level implementation is guaranteed to be testable for all single stuck-at faults in the combinational logic. No access to the memory elements is required. The test sequences for these faults can be obtained using combinational test generation techniques alone. It is shown that an intimate relationship exists between state assignment and the testability of a sequential machine. A technique is also presented of don't-care minimization and added observability which ensures fully testable machines