Multiple fault diagnosis in sequential circuits using sensitizing sequence pairs

The paper presents an approach to multiple fault diagnosis in sequential circuits by using input sequence pairs having sensitizing input pairs. This represents an extension of our previous work dealing with combinational circuits (N. Yanagida et al., 1995). After reviewing our previous method, we introduce an input sequence pair having sensitizing input pairs to diagnose multiple faults in a sequential circuit partitioned into subcircuits. We call such an input sequence pair, the sensitizing sequence pair. Next, we extend the use of the previous method for combinational circuits to sequential circuits. From a relation between a sensitizing path generated by a sensitizing sequence pair and a subcircuit, the proposed method deduces the suspected faults for the subcircuits, one by one, based on the responses observed at primary outputs without probing any internal line. The paper provides the first experimental reports on diagnostic results of the ISCAS circuits by using our diagnostic method for sequential circuits, without probing any internal line, any fault simulation, or fault enumeration.