Redundancy identification/removal and test generation for sequential circuits using implicit state enumeration

Finite state machine (FSM) verification based on implicit state enumeration can be extended to test generation and redundancy identification. The extended method constructs the product machine of two FSMs to be compared, and reachability analysis is performed by traversing the product machine to find any difference in I/O behavior. When an output difference is detected, the information obtained by reachability analysis is used to generate a test sequence. This method is complete, and it generates one of the shortest possible test sequences for a given fault. However, applying this method indiscriminately for all faults may result in unnecessary waste of computer resources. An efficient method based on reachability analysis of the fault-free machine (three-phase ATPG) in addition to the powerful but more resource-demanding product machine traversal is presented. The application of these algorithms to the problems of generating test sequences, identifying redundancies, and removing redundancies is reported