On the Use of Functional Test Generation in Diagnostic Test Generation for Synchronous Sequential Circuits

We study the relationship between diagnostic test generation for a gate-level fault model, which is used for generating diagnostic test sets for manufacturing defects, and functional test generation for a high-level fault model. In general, a functional fault may partially represent some of the effects of one gate-level fault but not another. Generating a test sequence for the functional fault is then likely to detect one gate-level fault but not the other, thus distinguishing the two faults. This relationship points to the ability to use a functional test generation procedure (that targets functional fault detection) as a way of generating diagnostic test sequences for gate-level faults. We use this observation in two ways. The more direct way is to define functional faults that correspond to the differences between pairs of gate-level faults. The second way is to use functional test sequences as diagnostic test sequences without explicitly considering gate-level faults. We support the use of the resulting procedures with experimental results.