Data path testability evaluation via functional testability measures

This paper addresses a testability evaluation approach applied to VLSI circuits at the data path level. The proposed approach uses new functional testability measures, which are based on the techniques of Reduced Ordered Binary Decision Diagrams (ROBDDs) representing functional primitives. These measures are: the Variable Testability Measure (VTM), for predicting the test-vector number of a data path and the controllability and observability measures, for identifying untestable parts in a data path. An objective function is developed, which enables estimation of area, delay and testability constraints of a data path. In this context, a structural modification in the data-path architecture is proposed, to make the design testable and/or to optimize the global cost determined by the objective function