Formal verification is an important issue in circuit and system design. In this context, Bounded Model Checking (BMC) is one of the most successful techniques. But even if all specified properties can be verified, it is difficult to determine whether they cover the complete functional behavior of a design. We propose a pragmatic approach to estimate coverage in BMC. The approach can easily be integrated in a BMC tool with only minor changes. In our approach, a coverage property is generated for each important signal. If the considered properties do not describe the signal's entire behavior, the coverage property fails and a counter-example is generated. From the counter-example an uncovered scenario can be derived. In this way the approach also helps in design understanding. Our method is demonstrated on a RISC CPU. Based on the results we identified coverage gaps. We were able to close all of them and achieved 100% functional coverage.

Verification is a major issue in circuit and system design. Formal methods like bounded model checking (BMC) can guarantee a high quality of the verification. There are several techniques that can check if a set of formal properties forms a complete specification of a design. But, in contrast to simulationbased methods, like random testing, formal verification requires a detailed knowledge of the design implementation. Finding the correct set of properties is a tedious and time consuming process. In this paper, two techniques are presented that provide automatic support for writing properties in a quality-driven BMC flow. The first technique can be used to analyze properties in order to remove redundant assumptions and to separate different scenarios. The second technique -inverse property checkingautomatically generates valid properties for a given expected behavior. The techniques are integrated with a coverage check for BMC. Using the presented techniques, the number of iterations to obtain full coverage can be reduced, saving time and effort.

No abstract

hijrhst wirtsrhsftlich susgebikleleli Trirhlorlthylen-Eiitfettungsiiitlii,cc wir0 geschildert. Der zweile Arbeitsgang der techiiisrheii Vorbereitung oliger l'eile is1 dns Entroslen; bei lrorkenen Teileri bildet es deli ersteii Arbeitsgang. Die t.heniische Entrostung ist wegen ihrer IJiiwirlschaftlichkeit wid RrolJen Eniltfindlirhkeit gegen die Luftfeuchtigkeit bei der Niichbehiiiidluny i n i prakt ischen \2'erltslltleiibelriebe uiidurrhfiihrbar untt tliiher iiirht besonders behiitidelt.' I n i gleichen Marie. \vie tler Auf\v:lntl mi IAohnen bei dieser iieues'eli Arbeitsweise nbgrnoiiinieti hiit, hill tlic Wirkung tlieses iieueii Stnhlsiitltlstrahlverfiihrcns gegeniiber dent iilten ~~iirttlentrostitrigsver~nhren mgeiioninien. -Oberbiiuriit K 6 t i i g , Mii:-tleburg: ,,Nrohn~li/itngrn iibrr di!. /~e t i~t s p r i t r / i i t n i jrnn Scliri/=trn.s/rirkrn trn k'n/ir:errgm."

No abstract