Test set and fault partitioning techniques for static test sequence compaction for sequential circuits

We propose a new static test set compaction method based on a careful exami nation of attributes of fault coverage curves. Our method is based on two k ey ideas: (1) fault-list and rest-set partitioning, and (2) vector re-order ing. Typically, the first few vectors of a test set detect a large number o f faults. The remaining vectors usually constitute a large fraction of the test set, bur these vectors are included to detect relatively few hard faul ts. We show that significant compaction can still be achieved by partitioni ng faults into hard and easy faults, and compaction is performed only for t he hard faults. This significantly reduces the computational cost for stati c test set compaction without affecting quality of compaction. The second k ey idea re-orders vectors in a test set by moving sequences that detect har d faults to the beginning of the test set. Fault simulation of the newly co ncatenated re-ordered test set results in the omission of several vectors s o that the compact test set is smaller than the original test set. Experime nts on several ISCAS 89 sequential benchmark circuits and large production circuits show that our compaction procedure yields significant test set red uctions in low execution times.