On test pattern compaction with multi-cycle and multi-observation scan test

This paper proposes a test compaction method for full scan circuits based on multiple capture clock cycles. The multiple cycle test applies more than one capture clock signals for a circuit after scan shift operation, while the capture clock cycle of the conventional scan test is one. Because every captured value at scan flip-flops is used for fault detection, the opportunity of fault detection for each fault increases. As a result, the number of test vectors would be decreased compared with the single cycle mode. Such a test compaction method would be useful in field test that requires less test data so as to store them on-chip. Experimental results show that the proposed method is effective for test compaction.