On synchronizable circuits and their synchronizing sequences

Synchronizing sequences are important in facilitating the test generation process for detectable faults, and in identifying undetectable faults. Synchronizing sequences are also important in determining whether an undetectable fault can be removed from a circuit without affecting its normal operation, i.e., in determining whether a fault is "redundant." In this work, we show a class of faults such that a synchronizing sequence for a faulty circuit can be obtained by repeating the synchronizing sequence of the fault-free circuit. Identification of such faults can be done by simulating the faulty circuits under the repeated synchronizing sequence of the fault-free circuit. We present experimental results to demonstrate the existence of such faults in benchmark circuits.