LOCSTEP: a logic simulation based test generation procedure

We present a method to generate test sequences that detect large numbers of faults (close to or higher than the number of faults that can be detected by deterministic methods) at a cost which is significantly lower than any existing test generation procedure. The generated sequences can be used alone or as prefixes to deterministic test sequences. To generate the sequences, we study the test sequences generated by several deterministic test generation procedures. We show that when deterministic test sequences are applied, the fault free circuits go through sequences of state transitions that have distinct characteristics which are independent of the specific circuit considered. Test sequences with the same characteristics are generated by using logic simulation only on the fault free circuit and considering several random patterns as candidates for inclusion in the test sequence at every time unit. By fault simulating these sequences, we find that the fault coverage achieved is very close to the fault coverage achieved by deterministic sequences and sometimes even higher. In most cases the fault coverage is higher than the fault coverage achieved by nondeterministic procedures based on genetic optimization.<>