Automatic extraction of the control flow machine and application to evaluating coverage of verification vectors

Simulation is still the primary, although inadequate, resource for verifying the conformity of a design to its functional specification. Fortunately, most errors in the early stages of design involve only the control flow in the circuit. We define the functional coverage of a given sequence of verification vectors as the amount of control behavior exercised by them. We present a novel technique for automatically extracting the control flow of a design on the basis of the underlying mathematical model. Significantly, this extraction is independent of the circuit description style. The Extracted Control Flow Machine (ECFM) is then used for estimation of functional coverage and to provide information that will help the designer improve the quality of his or her tests.