Fault diagnosis in complex digital circuits

A methodology is presented for diagnosing faults in complex, evolving digital circuits. The authors believe, however, that the analysis and the methods described can be applied to diagnose faults in the generic flow circuit, namely, information networks, thermal circuits, etc. A model useful for fault diagnosis is developed, and its application to troubleshooting digital circuits is discussed. The method involves three key steps: a given complex circuit may have to be transformed to a simpler representation, to one that corresponds to the model; basic techniques identified using the model can then be applied to troubleshoot it; and appropriate extensions may be needed for additional domain-specific or circuit-specific fault handling. A system that implements the methodology has been developed, and has been used to successfully troubleshoot a candidate complex digital circuit (of about 5-10% of the complexity of a VAX CPU)