Automatic test pattern generation: Difference between revisions

Revision as of 08:53, 19 July 2007

Revision as of 11:51, 31 July 2007

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ATPG can fail to find a test for a particular fault in at least two cases. First, the fault may be intrinsically undetectable, such that no patterns exist that can detect that particular fault. The classic example of this is a redundant circuit, designed so that no single fault causes the output to change. In such a circuit, any single fault will be inherently undetectable.

Second, it is possible that a pattern(s) exist, but the algorithm cannot find it. Since the ATPG problem is [[NP-complete]] (by reduction from the [[boolean satisfiability problem]]) there will be cases where patterns exist, but ATPG gives up since it will take an incredibly long time to find them (assuming [[Complexity classes P=NP and NPproblem|P≠NP]], of course).

== The Stuck-at fault model ==