Testability-preserving circuit transformations

Consideration is given to the synthesis of robustly path-delay-fault testable circuits and it is shown that a single property, ENF reducibility, unifies previous results on robust delay fault testability and multifault testability and proves new ones. The notion of ENF reducibility is used to show that a constrained version of a common area improving transformation, namely, algebraic resubstitution with complement, retains robust path-delay-fault testability. Thus, a more efficient means of synthesizing fully robustly path-delay-fault testable networks is given. The same property of ENF reducibility is used to show that constrained algebraic resubstitution with complement retains multifault irredundancy. Necessary and sufficient conditions are presented for transistor stuck-open fault testability in arbitrary, multilevel networks. It is shown that algebraic factorization, including the constrained use of the complement, can be used to synthesize fully stuck-open fault testable multilevel networks.<>