This paper discusses a new approach for generating test vectors, using test cultivation, for both combinational and sequential VLSI circuits described hierarchically at the transistor, gate, and higher levels. The approach is based on continuous mutation of a given input sequence and on analyzing the mutated vectors for selecting the test set. The hierarchical technique used in the analysis drastically reduces the memory requirements, allowing test generation for large circuits. The test cultivation algorithms are simulation-based and a test set can be cultivated for any circuit that can be simulated logically. In particular, general MOS digital designs can be handled, and both stuck-at and transistor faults can be accurately modeled. Using the approach, tests were generated with very high fault coverage for gate-level circuits as well as for transistor level circuits.
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