On computing signal probability and detection probability of stuck-at faults

Algorithms for the following two problems are presented: (1) computing detection probability of stuck-at faults (CDP), and (2) computing signal probability (CSP). These problems arise in the context of random testing, pseudorandom testing, and testability analysis of combinational circuits. The algorithm for CDP combines the notion of supergates and a refinement of th algorithm for CDP presented in the work of S. Chakravarty and H.B. Hunt, III (1986). The algorithm for CDP can be used to compute the exact value of detection probability of multiple stuck-at faults in circuits with multiple outputs. Single-input, single-output pseudo gates are inserted to model stuck-at faults and derive an equivalent single-output circuit. CDP is thus reduced to the problem of computing the probability distribution of the output over the set of four logic values {0, 1d, d¯}. The algorithm for CDP uses an efficient enumeration algorithm. The authors show how the enumeration algorithm can be used to refine the algorithm for CSP