Selecting Replacements for Undetectable Path Delay Faults

Abstract

Path selection procedures select the path delay faults that are the most important to detect as targets for test generation. When the criteria for path selection can be evaluated locally at the gate level, it is possible to consider the detectability of path delay faults during the path selection process. This flexibility does not exist if path selection is performed based on more complex conditions, or by a tool that cannot be modified to take into consideration the detectability conditions for path delay faults. For this scenario, this brief describes a procedure that accepts a set $P$ of path delay faults, and replaces every undetectable path delay fault $p \in P$ with a detectable path delay fault $r$ that is as similar to $p$ as possible. This brief defines similarity as the length of the longest contiguous subpath that is common to $p$ and $r$ . Experimental results demonstrate the extent to which similarity can be maintained when path delay faults that are associated with the longest paths are considered for benchmark circuits.