Input Cubes with Lingering Synchronization Effects and their Use in Random Sequential Test Generation

We define the notion of a lingering synchronization effect. Such an effect occurs when a primary input cube (an incompletely-specified primary input vector) determines the state of a circuit for several time units after it is applied. Such a primary input cube may prevent certain faults from being detected when it appears in a test sequence. It should therefore be avoided when the goal is to achieve a high fault coverage. We demonstrate that benchmark circuits have primary input cubes with small numbers of specified values (typically one or two), which have lingering synchronization effects. In some cases, the synchronization effects linger for large numbers of time units. We also describe a random test generation process that avoids primary input cubes with lingering synchronization effects, and achieves high fault coverage for benchmark circuits.