An algorithm for diagnostic fault simulation

In diagnostic testing faults detectable by test vectors are partitioned into groups. This partitioning is such that a fault is distinguishable from faults in all other groups, but is indistinguishable from those in its own group. Diagnostic fault coverage (DC) is defined as the number of fault groups divided by the total number of faults. We present a new diagnostic fault simulation algorithm that determines the DC of given test vectors and produces a fault dictionary. For each vector, we begin with detected fault list at each primary output obtained from a convetional fault simulator. For the vector being simulated each fault is assigned a detection index that uniquely specifies its detection status at all primary outputs. Fault list is then partitioned. Faults with different detection index are distinguished by the simulated vector and are kept in separate groups. Any fault in a group by itself is dropped from further simulation with subsequent vectors for which its detection index remains unknown (X). After simulation of each vector, the cumulative DC is obtained by counting the fault groups. Fault dictionary syndrome for a fault is the array of its detection indexes.