A simulation-based method for generating tests for sequential circuits

In a recent work of the authors (1987), a simulation-based directed search approach for generating test vectors for combinational circuits was proposed. In this method, the search for a test vector is guided by a cost function computed by the simulator. Event-driven simulation deals with circuit delays in a very natural manner. Signal controllability information required for the cost function is incorporated in a new form of logic model called the threshold-value model. These concepts are extended to meet the needs of sequential circuit test generation. Such extensions include handling of unknown values, analysis of feedback loops, and analysis of race conditions in the threshold-value model. A threshold-value sequential test generation program, TVSET, is implemented. It automatically initializes the circuit and generates race-free tests for synchronous and asynchronous circuits