Diagnostic of path and gate delay faults in non-scan sequential circuits

The goal of fault diagnosis is to identify the causes of device failures. Different techniques have been proposed for stuck-at fault diagnosis in combinational as well as sequential circuits. On the other side, diagnosis of delay faults has received attention for the first category of circuits, but not for synchronous sequential circuits. So, this paper concerns delay fault diagnosis for non-scan circuits. A preliminary version of the proposed method is first given. New concepts for allowing path tracing in the proposed diagnosis process (identification of self-masking) are also presented. As the method is based on path tracing through the sequential circuit, gate delay faults as well as path delay faults are considered and may be located in a faulty machine. Results of experiments on ISCAS-89 benchmark circuits are finally discussed