Selective Low-Care Coding: A Means for Test Data Compression in Circuits with Multiple Scan Chains

Youhua SHI  Nozomu TOGAWA  Shinji KIMURA  Masao YANAGISAWA  Tatsuo OHTSUKI  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E89-A   No.4   pp.996-1004
Publication Date: 2006/04/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e89-a.4.996
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Selected Papers from the 18th Workshop on Circuits and Systems in Karuizawa)
test data compression,  test channels,  scan test,  

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This paper presents a test input data compression technique, Selective Low-Care Coding (SLC), which can be used to significantly reduce input test data volume as well as the external test channel requirement for multiscan-based designs. In the proposed SLC scheme, we explored the linear dependencies of the internal scan chains, and instead of encoding all the specified bits in test cubes, only a smaller amount of specified bits are selected for encoding, thus greater compression can be expected. Experiments on the larger benchmark circuits show drastic reduction in test data volume with corresponding savings on test application time can be indeed achieved even for the well-compacted test set.