On multi‐cycle test cubes

This article studies the generation of test sets that consist of multi‐cycle test cubes. Such test cubes have partially‐specified scan‐in states, and several functional clock cycles between scan operations. Test cubes are important for test data compression. In addition, multi‐cycle tests can detect delay defects that are not detected by single‐cycle tests. The use of multi‐cycle test cubes is shown to reduce the number of test cubes required for detecting single stuck‐at faults compared with the case where single‐cycle test cubes are used. This article also shows that a multi‐cycle test cube for a single stuck‐at fault can have fewer specified scan‐in values than a single‐cycle test cube for the same fault. As a result, multi‐cycle test cubes can be more effective for test data compression. This article also discusses the conditions under which multi‐cycle test cubes can be merged in order to further reduce the number of test cubes in a test set.