Non-scan Design for Testability for Synchronous Sequential Circuits Based on Fault-Oriented Conflict Analysis

Dong XIANG  Shan GU  Hideo FUJIWARA  

IEICE TRANSACTIONS on Information and Systems   Vol.E86-D   No.11   pp.2407-2417
Publication Date: 2003/11/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Fault Tolerance
at-speed test,  conflict,  containing assignment,  non-scan design for testability,  sequential depth for testability,  

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A two stage non-scan design for testability method is proposed. The first stage selects test points based on an earlier testability measure conflict. A new design for testability algorithm is proposed to select test points by a fault-oriented testability measure conflict+ in the second stage. Test points are selected in the second stage based on the hard faults after the initial ATPG run of the design for testability circuit in the preliminary stage. The new testability measure conflict+ based on conflict analysis of hard-faults in the process of test generation is introduced, which emulates most general features of sequential ATPG. The new testability measure reduces testability of a fault to the minimum D or controllability of the primary outputs, and therefore, does not need observability measure any more. Effective approximate schemes are adopted to get reasonable estimation of the testability measure. A couple of effective techniques are also adopted to accelerate the process of the proposed design for testability algorithm. Experimental results show that the proposed method gets even better results than two of the recent non-scan design for testability methods nscan and lcdft.