Diagnosis of Faults in Modular Trees

Diagnosis of stuck-at faults (s-a-f's) in modular trees is studied. Detection conditions for each distinguishable s-a-f in a module are derived. For single s-a-f's, the detection conditions are easily partitioned to achieve fault location by performing a small number of additional tests. A multiple s-a-f that produces the same test result as a single s-a-f can be located by applying additional tests whose number grows with the tree depth. All other multiple s-a-f's are detected but cannot be located. In this paper location algorithms for combinational modular trees are presented in detail. They are then modified to locate faults in modular trees which realize arbitrary definite machines. Since a pair of these tree structures can be connected to realize arbitrary sequential machines, the results derived here are useful in diagnosing sequential machines. The ability to diagnose faults, combined with the fact that the function of the tree is easily altered, makes this structure attractive in reconfiguration applications. In particular, application to array processors is suggested.