Preponing Fault Detections for Test Compaction Under Transparent Scan

Abstract

A test compaction procedure under transparent scan can compact a scan-based test set that contains a minimum number of tests. The additional test compaction can be important in applications that require highly compacted test sets. Transparent scan views a scan-based test set as a sequence of scan shift and functional capture cycles and allows the two types of clock cycles to appear in arbitrary sequences. The contribution of this brief is to suggest that one of the reasons for the effectiveness of transparent scan for test compaction is its ability to prepone fault detections by replacing scan shift with functional capture cycles when faults are activated during scan shift cycles. When fault detections are preponed, clock cycles around the original detection clock cycles become unnecessary and can be omitted. This view results in a new test compaction procedure that focuses on steps that contribute to test compaction, thus reducing the computational effort of test compaction compared with general-purpose test compaction procedures.