Test compaction methods for transition faults under transparent-scan

Abstract

Transparent-scan was proposed as an approach to test generation and test compaction for scan circuits. Its effectiveness was demonstrated earlier in reducing the test application time for stuck-at faults. The authors show that similar advantages exist when considering transition faults. The authors first show that a test sequence under the transparent-scan approach can imitate the application of broadside tests for transition faults. Test compaction can proceed similar to stuck-at faults by omitting test vectors from the test sequence. Two new approaches for enhancing test compaction are described. Under the first approach, additional broadside tests are embedded in the transparent-scan sequence without increasing its length or reducing its fault coverage. This allows additional vectors to be omitted from the test sequence. Under the second approach, the order by which broadside tests appear in the transparent-scan sequence is modified so as to reduce the compacted sequence length. The authors also discuss the generation of several transparent-scan sequences of limited lengths by partitioning the broadside tests among different sequences.