X-alignment techniques for improving the observability of response compactors

Ozgur Sinanoglu, Sobeeh Almukhaizim

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


Despite the advantages of performing response compaction in Integrated-Circuit (IC) testing, unknown response bits (x's) inevitably reflect into loss in test quality. The distribution of these x's within the captured response, which varies for each test pattern, directly impacts the number of scan cells observed through the response compactor. In this work, we propose a two-dimensional X-alignment technique in order to judiciously manipulate the distribution of x's in the test response prior to its compaction. The controlled response manipulation is performed on a per pattern basis, in the form of scan chain delay and intra-slice rotate operations, and with the objective that x's are aligned within as few scan slices and chains as possible. Consequently, a larger number of scan cells are observed after compaction for any test pattern. The computation of the control data, i.e., rotate and delay bits, is formulated as a MAX-SAT problem, and efficient heuristics are provided. The proposed technique is test set independent, leading to a generic, simple, and cost-effective hardware implementation. The X-alignment technique can be utilized with any response compactor to manipulate the x-distribution in favor of the compactor, thus improving the test quality.

Original languageEnglish (US)
Title of host publicationInternational Test Conference, ITC 2009 - Proceedings
StatePublished - Dec 15 2009
EventInternational Test Conference, ITC 2009 - Austin, TX, United States
Duration: Nov 1 2009Nov 6 2009

Publication series

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


OtherInternational Test Conference, ITC 2009
Country/TerritoryUnited States
CityAustin, TX

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Applied Mathematics


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