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VLSI Design
Volume 10 (1999), Issue 2, Pages 127-141

Signature Analysis for Test Responses of Sequential Circuits

Institute of Computer Design and Fault Tolerance, University of Karlsruhe, Karlsruhe D-76128, Germany

Received 10 November 1997; Accepted 6 November 1998

Copyright © 1999 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.


Many test schemes use signature analyzers to compact the responses of a circuit under test. Unfortunately, there can be some faulty circuits with erroneous test responses but exactly the same signature as in the fault-free case. Hence, methods are required to determine how many faults become undetectable due to aliasing. Whereas previous work concentrated on combinational circuits, this paper investigates signature analysis for a wide range of sequential circuits, where the errors in successive responses are correlated. It is shown that for almost all faults of these circuits the probability of aliasing in a signature analyzer with k bits asymptotically approaches 2k or is 0 if a signature analyzer with an irreducible characteristic polynomial is used and certain test lengths are avoided. The limiting value can be used as a good approximation for practical test lengths. These results are particularly useful for advanced built-in self-test techniques with low hardware overhead.