Extended Selective Encoding of Scan Slices for Reducing Test Data and Test Power

Yinhe HAN
Xiaowei LI

IEICE TRANSACTIONS on Information and Systems   Vol.E93-D    No.8    pp.2223-2232
Publication Date: 2010/08/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.E93.D.2223
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Information Network
selective encoding,  test data compression,  test power reduction,  flexible grouping,  X-filling,  

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Test data volume and test power are two major concerns when testing modern large circuits. Recently, selective encoding of scan slices is proposed to compress test data. This encoding technique, unlike many other compression techniques encoding all the bits, only encodes the target-symbol by specifying a single bit index and copying group data. In this paper, we propose an extended selective encoding which presents two new techniques to optimize this method: a flexible grouping strategy, X bits exploitation and filling strategy. Flexible grouping strategy can decrease the number of groups which need to be encoded and improve test data compression ratio. X bits exploitation and filling strategy can exploit a large number of don't care bits to reduce testing power with no compression ratio loss. Experimental results show that the proposed technique needs less test data storage volume and reduces average weighted switching activity by 25.6% and peak weighted switching activity by 9.68% during scan shift compared to selective encoding.