Multiple distributions for biased random test patterns

An efficient method has been presented to compute multiple distributions for random patterns, which can be applied successively. Using multiple distributions, all combinational circuits can be made random-testable, and complete fault coverage is provided by a few thousands of random patterns. The differently weighted random test sets can be applied to scan path circuits using an external chip, combining the advantages of a low cost test and of high fault coverage. Several facts about testing by random patterns have been proven. It has been shown that the number of random patterns required for a certain fault coverage can be computed without regarding the pseudorandom property and with the independence assumption for fault detection