On the eliminating of parameters α and β in STAFAN

STAFAN algorithm (1985) is regarded as a good alternative to fault simulation of digital circuits. However, this algorithm has two parameters α and β to be determined by fault simulation and so it is of no practical uses. This article analyzes the probability distribution of random signals at circuit nodes, and proves that controllability is in normal distribution. Thus the unbiasing estimate of fault detection probability can be obtained. Moreover, according to the concept of observability, we can eliminate parameter β. For actual circuits the fault coverage obtained from the modified STAFAN agrees favorably with the fault simulation results