Delay test generation. I. Concepts and coverage metrics

An approach to test for delay faults is presented. A variable size delay fault model is used to represent these failures. The nominal gate delays with the manufacturing tolerances are an integral part of the model and are used in the propagation of simplified waveforms through the logic network. The faulty waveforms are functions of the variable-size delay fault. For each fault and test pattern, a threshold is computed such that this fault is detected if its size exceeds ε. This threshold is used (along with the minimum slack at the fault site) to determine a metric called quality. The quality of detection for a fault measures how close the test came to exposing the ideally smallest-size fault at that point. This metric (together with the traditional fault coverage) gives a complete measure of the goodness of the test