Path delay fault diagnosis in combinational circuits with implicit fault enumeration

A new methodology involving effect-cause analysis has been demonstrated for the diagnosis of path delay faults. The paper illustrates a structural representation, called the suspect circuit, of all the possible path delay faults in a faulty circuit. This representation has been used to design efficient algorithms that enable us to manipulate the suspect faults without having to enumerate them explicitly. Procedures for removing fault-free paths from the list of suspect faults have been implemented to improve the diagnostic resolution. Moreover, efficient data structures are used to complement the procedures and reduce the memory footprint of the algorithms. Results indicate that the diagnostic resolution obtained is very high and includes all possible causes of the observed delay faults.