On Non-Statistical Techniques for Fast Fault Coverage Estimation

We present fast, dynamic fault coverage estimation techniques for sequential circuits that achieve high degrees of accuracy and significant reductions in the number of injected faults and faulty-event evaluations. In the proposed techniques, we dynamically reduce injection of hyperactive faults as well as faults whose effects never propagate to a flip-flop or primary output. Suppression and over-specification of potential fault-effects are also investigated to reduce faulty-event evaluations. Experiments show that our methods give very accurate estimates with frequently greater speedups than the sampling techniques for most circuits. Most significantly, the proposed techniques can be combined with the sampling approach to obtain speedups comparable to small sample sizes and retain estimation accuracy of large fault samples.