Test generation for partially-functional broadside tests

Yixi Yang, Purdue University

Abstract

Scan-based tests allow a circuit to enter states that the circuit does not visit during functional operation. Testing a circuit using nonfunctional broadside tests will cause overtesting of delay faults, which may cause a good chip to fail the test due to functionally infeasible paths or excessive power demand that would not occur during functional operation. Functional broadside tests only allow reachable states, which the circuit can enter during functional operation, as scan-in states in order to eliminate overtesting. However, the exclusive use of functional broadside tests will cause a loss of fault coverage, which might lead to reliability issues. Partially-functional broadside tests are designed to improve the fault coverage achievable by using functional broadside tests. Partially-functional broadside tests allow unreachable states to be scanned in, but they require a known Hamming distance between an unreachable scan-in state and a reachable state. In this way, they guarantee measurable deviations from functional operation conditions while tests are applied. In this thesis, a close-to-complete test generation procedure for partially-functional broadside tests targeting transition faults is described for both synchronizable circuits and non-synchronizable circuits. This procedure is guaranteed to find a test for every detectable fault, while targeting the test with a low Hamming distance from a reachable state. Experimental results show that it is possible to generate a test set that achieves the same fault coverage as a broadside test set with unconstrained scan-in states. The switching activity is used as an indirect indicator of the deviation from functional operation conditions while applying the tests.

Degree

M.S.E.C.E.

Advisors

Pomeranz, Purdue University.

Subject Area

Electrical engineering

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