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Design and analysis of skewed-distribution scan chain partition for improved test data compression

Code-based test data compression schemes encode symbols in the test data with predetermined codewords so that data volume can be reduced. The compression efficiency is affected by the distribution of data symbols. In this paper, we first analyze the factors that affect the encoding efficiency in various codes, and then propose a skewed-distribution scan chain partitioning scheme, in which the distribution of 0's and 1's are changed in different parts of the scan chain. Both analytical and experimental results confirm that the scheme can effectively improve compression efficiency, while the routing penalty due to the partitioning method is limited.