Verification of designs containing black boxes

Often modern designs contain regions where the implementation of certain components is not (fully) known. These regions are called black boxes in the following. They occur e.g. if different designers work on a project in parallel or if IP cores are used. An approach based on a symbolic representation of characteristic functions for verifying circuits with black boxes is presented. We show that by this method more faults can be detected than with pure binary simulation and symbolic simulation using BDDs, respectively, only. This results from the formulation of our algorithm that allows implications over the black box. Experimental results are given to show what parts of a design can be proven to be correct, if black boxes are assumed. Of course, the probability for the detection of a fault in general depends on the size of the unknown regions. But fault injection experiments on benchmarks show that for many circuits, even up to 90% of the faults are detected, even though large parts of the design are unspecified.