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VLSI Design
Volume 2011 (2011), Article ID 756561, 8 pages
Research Article

Weighted Transition Based Reordering, Columnwise Bit Filling, and Difference Vector: A Power-Aware Test Data Compression Method

1PG (VLSI Design), Nirma University, Ahmedabad 382481, India
2Indian Institute of Space Science & Technology, Tiruvanthapuram, India

Received 29 March 2011; Revised 14 May 2011; Accepted 29 July 2011

Academic Editor: Yangdong Deng

Copyright © 2011 Usha Mehta et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Test data compression is the major issues for the external testing of IP core-based SoC. From a large pool of diverse available techniques for compression, run length-based schemes are most appropriate for IP cores. To improve the compression and to reduce the test power, the test data processing schemes like “don't care bit filling” and “reordering” which do not require any modification in internal structure and do not demand use of any test development tool can be used for SoC-containing IP cores with hidden structure. The proposed “Weighted Transition Based Reordering-Columnwise Bit Filling-Difference Vector (WTR-CBF-DV)” is a modification to earlier proposed “Hamming Distance based Reordering—Columnwise Bit Filling and Difference vector.” This new method aims not only at very high compression but also aims at shift in test power reduction without any significant on-chip area overhead. The experiment results on ISCAS89 benchmark circuits show that the test data compression ratio has significantly improved for each case. It is also noteworthy that, in most of the case, this scheme does not involve any extra silicon area overhead compared to the base code with which it used. For few cases, it requires an extra XOR gate and feedback path only. As application of this scheme increases run length of zeroes in test set, as a result, the number of transitions during scan shifting is reduced. This may lower scan power. The proposed scheme can be easily integrated into the existing industrial flow.