A Multicycle Test Set Based on a Two-Cycle Test Set With Constant Primary Input Vectors

Test compaction can be achieved by using multicycle tests. To avoid the computationally intensive process of sequential test generation, multicycle tests can be generated by extending two-cycle tests. However, the scan-in state of a two-cycle test is not always effective for a multicycle test when the primary input vectors are held constant during the functional clock cycles of a test. This paper studies the extent of this issue by considering exhaustive two-cycle and multicycle test sets with constant primary input vectors for finite-state machine benchmarks. Based on the results of this study, it describes an efficient test compaction procedure that modifies selected two-cycle tests in a given test set in order to make them more effective as a source for multicycle tests with constant primary input vectors. Experimental results are presented to demonstrate the importance of this step to test compaction.