Test Set and Fault Partitioning Techniques for Static Test Sequence Compaction for Sequential Circuits

Abstract

We propose a new static test set compaction method based on a careful examination of attributes of fault coverage curves. Our method is based on two key ideas: (1) fault-list and test-set partitioning, and (2) vector re-ordering. Typically, the first few vectors of a test set detect a large number of faults. The remaining vectors usually constitute a large fraction of the test set, but these vectors are included to detect relatively few hard faults. We show that significant compaction can still be achieved by partitioning faults into hard and easy faults, and compaction is performed only for the hard faults. This significantly reduces the computational cost for static test set compaction without affecting quality of compaction. The second key idea re-orders vectors in a test set by moving sequences that detect hard faults to the beginning of the test set. Fault simulation of the newly concatenated re-ordered test set results in the omission of several vectors so that the compact test set is smaller than the original test set. Experiments on several ISCAS 89 sequential benchmark circuits and large production circuits show that our compaction procedure yields significant test set reductions in low execution times.