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

Abstract

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.

FF-Control Point Insertion (FF-CPI) to Overcome the Degradation of Fault Detection under Multi-Cycle Test for POST

“…SEQ-OB technique proposed in [10] that directly observes the capture values of FFs during the multi-cycle test is conducted to handle the fault effects vanishing problem. In [19], in order to highlight the effect of FF-CPI technique, all FFs of the circuit were used for SEQ-OB to avoid the impact of fault effects vanishing on fault detection.…”

“…Copyright c 2020 The Institute of Electronics, Information and Communication Engineers that denotes the fault effects excited at some intermediate capture cycles might disappear before their effects are propagated to the final capture cycle for observation due to the expanded long propagation path that would cause fault coverage loss [13]- [16]. To address the fault effects vanishing problem, a sequential observation (SEQ-OB) technique that directly observes the values of small part of Flip-Flops (FFs) at each capture cycle has been introduced in [10] and [13].…”