Align-Encode: Improving the encoding capability of test stimulus decompressors

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


While test stimulus compression helps reduce test time and data volume, and thus alleviates test costs, the delivery of certain test vectors may not be possible, leading to test quality degradation. Whether a test vector is encodable in the presence of a decompressor strongly hinges on the distribution ofits care bits. In this paper, wepresent a technique that provides an on-chip capability tojudiciously manipulate care bit distribution of a test vector We thus propose a hardware block, namely, Align-Encode, to be utilized along with any decompressor to boost the effectiveness ofthe decompressor. Align-Encode is reconfigured on a per pattern basis to delay the shift-in operations in selected scan chains, in order to align the scan slices in such a way that more test vectors become encodable. The reconfigurability ofAlign-Encode provides a test pattern independent solution, wherein any given set oftest vectors can be analyzed to compute the proper delay information. We map the delay computation problem to the maximal clique problem, and utilize an efficient heuristic to provide a near-optimal solution. Experimental results also justify the test pattern encodability enhancements that Align-Encode delivers, enabling significant test quality improvements andlor test cost reductions even when used with simple decompressors.

Original languageEnglish (US)
Title of host publicationProceedings - International Test Conference 2008, ITC 2008
StatePublished - 2008
EventInternational Test Conference 2008, ITC 2008 - Santa Clara, CA, United States
Duration: Oct 28 2008Oct 30 2008

Publication series

NameProceedings - International Test Conference
ISSN (Print)1089-3539


OtherInternational Test Conference 2008, ITC 2008
Country/TerritoryUnited States
CitySanta Clara, CA

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Applied Mathematics


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