Pattern encodability enhancements for test stimulus decompressors

Nader Alawadhi, Ozgur Sinanoglu, Mohammed Al-Mulla

Research output: Chapter in Book/Report/Conference proceedingConference contribution


While scan-based compression is widely utilized in order to alleviate the test time and data volume problems, the overall compression level is dictated not only by the chain to channel ratio but also the ratio of encodable patterns. Aggressively increasing the number of scan chains in an effort to raise the compression levels may reduce the ratio of encodable patterns, degrading the overall compression level. In this paper, we present various methods to improve the ratio of encodable patterns. These methods are based on manipulating the care bit distribution of an unencodable pattern, thereby rendering it compliant with the correlation induced by the decompressor, and thus converting it into an encodable pattern. The proposed methods target improvements over fan-out and XOR decompressors, while they can be utilized to enhance other types of decompressors, such as multiplexer-based ones. Care bit manipulation is effected in the form of selective chain delay, selective slice rotate/invert, or both. By developing computationally efficient algorithms and cost-effective hardware blocks for these manipulation methods, we show that the encodability, and thus the compression levels, of stimulus decompressors can be significantly improved through the proposed practical and design flow compatible solution.

Original languageEnglish (US)
Title of host publicationProceedings - 2010 19th IEEE Asian Test Symposium, ATS 2010
Number of pages6
StatePublished - 2010
Event2010 19th IEEE Asian Test Symposium, ATS 2010 - Shanghai, China
Duration: Dec 1 2010Dec 4 2010

Publication series

NameProceedings of the Asian Test Symposium
ISSN (Print)1081-7735


Other2010 19th IEEE Asian Test Symposium, ATS 2010


  • Pattern encodability
  • Scan-based test
  • Test stimulus compression
  • VLSI test

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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