Multiple observation time single reference test generation using synchronizing sequences

A synchronizing sequence drives a circuit from an arbitrary power-up state into a unique state. A framework and algorithms for test generation based on the multiple observation time strategy are developed by taking advantage of synchronizing sequences. Though it has been shown that the multiple observation time strategy can provide a higher fault coverage than the conventional single observation time strategy, until now the multiple observation time strategy has required a very complex tester operation model and its overhead. However, when a circuit is synchronizable, test generation can employ the multiple observation time strategy and provide better fault coverages, while using the conventional tester operation model. It is shown that the same fault coverage can be achieved in both tester operation models if the circuit under test generation is synchronizable. The authors investigate how a synchronizing sequence simplifies test generation and allows one to use the simpler tester operation model