Abstract：A new approach to calculate fault detection probabilities is presented. The fault-free simulation is used in this approach. The quantities of controllabilities and observabilities are defined as probabilities of controlling and observing the nodes in the circuit. The probability distribution of random signals at circuit nodes is analyzed, and it is proved that controllability is in normal distribution. Thus the unbiasing estimate of fault detection probability can be obtained. According to the concept of observability, the fanout nodes are dealt with. For actual circuits the fault coverage obtained from this approach agrees favorably with the fault simulation results.
1995, Vol. 17 
