Path Selection for Transition Path Delay Faults

Abstract

We propose a path selection criterion to improve the coverage of small delay defects. Under this criterion, every line in the circuit is covered by one of the longest testable paths or subpaths that goes through it. Earlier criteria that considered only complete paths (from inputs to outputs) did not use longest testable subpaths, which may be longer than the longest complete testable paths. Earlier criteria that considered subpaths considered only subpaths of longest paths. We apply the proposed criterion to a delay fault model called the transition path delay fault model. This model was introduced to capture both small and large delay defects. We present experimental results to demonstrate that consideration of subpaths improves the circuit coverage relative to the case where only complete paths are allowed.