X-Handling for Current X-Tolerant Compactors with More Unknowns and Maximal Compaction

Youhua SHI  Nozomu TOGAWA  Masao YANAGISAWA  Tatsuo OHTSUKI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E92-A   No.12   pp.3119-3127
Publication Date: 2009/12/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E92.A.3119
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on VLSI Design and CAD Algorithms)
Category: Logic Synthesis, Test and Verfication
scan test,  test data compression,  X-masking,  

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This paper presents a novel X-handling technique, which removes the effect of unknowns on compacted test response with maximal compaction ratio. The proposed method combines with the current X-tolerant compactors and inserts masking cells on scan paths to selectively mask X's. By doing this, the number of unknown responses in each scan-out cycle could be reduced to a reasonable level such that the target X-tolerant compactor would tolerate with guaranteed possible error detection. It guarantees no test loss due to the effect of X's, and achieves the maximal compaction that the target response compactor could provide as well. Moreover, because the masking cells are only inserted on the scan paths, it has no performance degradation of the designs. Experimental results demonstrate the effectiveness of the proposed method.