CLASSIFICATION AND TEST-GENERATION FOR PATH-DELAY FAULTS USING SINGLESTRUCK-AT FAULT-TESTS

We classify all path-delay faults of a combinational circuit into thre e categories: singly-testable (ST), multiply-testable (MT), and singly -testable dependent (ST-dependent). The classification uses any unalte red single stuck-at fault test generation tool. Only two runs of this tool on a model network derived from the original network are performe d. As a by-product of this process, we generate single and multiple in put change delay tests for all testable faults. With these tests, we e xpect that most defective circuits are identified. All ST faults are g uaranteed detection in the case of a single fault, and some may be gua ranteed detection through robust and validatable nonrobust tests even in the case of multiple faults. An ST-dependent fault can affect the c ircuit speed only if certain ST faults are present. Thus, if all ST fa ults are tested, the ST-dependent faults need not be tested. MT faults cannot be guaranteed detection, but affect the speed only if delay fa ults simultaneously exist on a set of paths, none of which is ST. Exam ples and results on several ISCAS '89 benchmarks are presented. The me thod of classification through test generation using a model network i s complex and can be applied to circuits of moderate size. For larger circuits, alternative methods will have to be explored in the future.