Structural Factors in the Fault Diagnosis of Combinational Networks

The problem of fault detection and diagnosis of irredundant multiple-output combinational networks is discussed from a purely structural viewpoint, i.e., with the functions of the network components essentially ignored. Two structural models for a network are given in the form of labeled directed graphs. Graph theoretic concepts are introduced, and theorems are developed which give necessary conditions and sufficient conditions for the detectability of faults at particular primary outputs based solely on the structure of the network. Procedures are then presented for obtaining the structural diagnostic resolution for both line and logic module faults. Finally, an application, test point placement for increased network maintainability, is considered.