Signature analysis usage for multiple fault isolation

摘要

Test equipment and test methods employing signature analysis to achieve fault isolation of parts contained in digital modules. Fault free signatures of a digital module are stored in a lookup table that are derived from physical measurement or simulation of all parts. All of the parts in the functional digital module are shorted and opened (either physically or by simulation) and each of their resulting faulty signatures are recorded in a storage device. Each signature with its corresponding faulty part is stored in the lookup table or memory. Test input signals are then applied to a tested digital module, and outputs of all parts thereof are applied to masking circuitry which allows sequential selective masking of all parts but one, for each part on the tested digital module. Outputs of the masking circuitry are applied to a multiple input shift register signal analyzer that performs pass/fail signature analysis using the applied signals. When a failure occurs during testing of the tested digital module, comparator circuitry is used to find a corresponding signature match to the stored faulty signatures. A message is then sent as an output from the comparator circuitry identifying the failed part so that the tested digital module can be repaired. The present invention does not require expensive automatic test equipment and therefore provides a more cost-effective approach to failure analysis.