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VLSI Design
Volume 12 (2001), Issue 4, Pages 515-525

Test Generators Need to be Modified to Handle CMOS Designs

ECE Dept., New Jersey Institute of Technology, University Heights, Newark 07102-1982, NJ, USA

Received 15 August 1999; Revised 11 September 2000

Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


CMOS designs have some unique properties that prevent existing test generators from computing a test vector for a fault when one might exist. The problem lies in the premises laid out on what it takes to detect a stuck-at fault. The basic premise that states that it is required to set a line to 0(1) in order to detect a stuck-at 1(0) fault, and then propagate the error to an observable point, needs to be re-examined. This is due to the existence of indeterminate states throughout the logic. The paper distinguishes between the traditional test vector (here called a hard-detect), and a potential test vector (here called a soft-detect). Our proposed test set is the union of hard and soft-detects. We also re-examine the issue of redundancy and show that it needs to be re-defined in order to comply with CMOS technology behavior.

This paper shows several examples to illustrate the problem; describes what it takes in order to remedy it; proposes possible enhancements to existing test generation algorithms, and outlines the risks faced in the event that no correcting steps are taken.