Periodic Scan-In States to Reduce the Input Test Data Volume for Partially Functional Broadside Tests

Abstract

This article describes a procedure for test data compression targeting functional and partially functional broadside tests. The scan-in state of such a test is either a reachable state or has a known Hamming distance from a reachable state. Reachable states are fully specified, while the popular LFSR -based test data compression methods require the use of incompletely specified test cubes. The test data compression approach considered in this article is based on the use of periodic scan-in states. Such states require the storage of a period that can be significantly shorter than a scan-in state, thus providing test data compression. The procedure computes a set of periods that is sufficient for detecting all the detectable target faults. Considering the scan-in states that the periods produce, the procedure ranks the periods based on the distances of the scan-in states from reachable states, and the lengths of the periods. Functional and partially functional broadside tests are generated preferring shorter periods with smaller Hamming distances. The results are compared with those of an LFSR -based approach.