On Synchronizing Sequences and Test Sequence Partitioning

We consider two topics related to testing of synchronous sequential circuits. The first topic deals with synchronizable circuits and their synchronizing sequences. Synchronizing sequences are important in facilitating the test generation process for detectable faults, and in identifying undetectable faults. They are also important in determining whether an undetectable fault can be removed from a circuit without affecting its normal operation. We show a class of faults for which a synchronizing sequence for the faulty circuit can be easily determined from the synchronizing sequence of the fault free circuit. We also consider circuits that have a reset mechanism, and show how reset can ensure that no single fault would cause the circuit to become unsynchronizable. The second topic we consider deals with test sequence partitioning to speed up static test compaction. We propose a procedure for partitioning a given test sequence into subsequences such that the cumulative fault coverage of all the subsequences, when applied as independent test sequences, is equal to the fault coverage of the original sequence. Each subsequence can then be compacted independently.