Weighting system for testing of circuits utilizing determination of

Abstract

In integrated circuit testing, a system is provided for reducing testing time by decreasing the number of test vectors or patterns while maintaining high fault coverage through utilizing lists of undetected faults in an integrated circuit to determine the optimal weighting for a weighted random pattern generator that is used for testing the integrated circuit. Undetected faults are derived from testing a model of the circuit under test with a uniform weight pattern, with the circuit modified with each fault from a list of anticipated faults. Undetected faults from this first pass are used to generate another set of weights which are then used to apply test signals to the circuit for generating a further but diminished list of undetected faults. This process is iterative and is continued until the number of undetected faults is either zero or some low acceptable number. The set of weights generated in this iterative process is then used in the weighted random pattern generator for applying test signals to actual circuits. As part of this process, for circuit elements requiring diametrically opposed input signals, such as AND gates and OR gates where a single set of input signals is inappropriate, this conflict is resolved through detecting the fact that for one part, all faults are detected, and then generating test vectors suitable for the opposite circuit. This allows the testing of circuits piece by piece.