On non-statistical techniques for fast fault coverage estimation

We present fast, dynamic fault coverage estimation techniques for sequentia l circuits that achieve high degrees of accuracy and significant reductions in the number of injected faults and faulty-event evaluations. In the prop osed techniques, we dynamically reduce injection of hyperactive faults as w ell as faults whose effects never propagate to a flip-flop or primary outpu t. Suppression and over-specification of potential fault-effects are also i nvestigated to reduce faulty-event evaluations. Experiments show that our m ethods give very accurate estimates with frequently greater speedups than t he sampling techniques for most circuits. Most significantly, the proposed techniques can be combined with the sampling approach to obtain speedups co mparable to small sample sizes and retain estimation accuracy of large faul t samples.