A Mixed Approach for Unified Logic Diagnosis

This paper presents a diagnosis methodology targeting most of the fault models used in practice today. This methodology is intended to be used to diagnose faulty behaviors in nanometric circuits for which the classical stuck-at fault model is far to cover all the realistic failures. The first phase of this methodology consists in the application of an Effect-Cause approach which relies on the two following main operations. The first one is based on critical path tracing (CPT) and consists in identifying lines in the Circuit Under Test (CUT) which can be the source of observed errors. The second one consists in allocating a set of possible fault models to each suspected line. In a second phase, we resort to a Cause-Effect approach applied on the set of suspects previously identified to prune the unlikely candidates and thus improve diagnosis resolution. The main advantage of this method is that it considers logical effects of the faults and does not need to handle each specific fault model explicitly during the diagnosis process. Experiments on ISCAS´89 and ITC´99 benchmark circuits show the efficiency of the proposed method in terms of diagnosis resolution.