Towards a Formal Semantics of Ver- Ilog Using Duration Calculus towards a Formal Semantics of Ver- Ilog Using Duration Calculus

The mission of UNU/IIST is to assist developing countries in the application and development of software technology. UNU/IIST contributes through its programmatic activities: 1. advanced development projects in which software techniques supported by tools are applied, 2. research projects in which new techniques for software development are investigated, 3. curriculum development projects in which courses of software technology for universities in developing countries are developed, 4. courses which typically teach advanced software development techniques, 5. events in which conferences and workshops are organised or supported by UNU/IIST, and 6. dissemination, in which UNU/IIST regularly distributes to developing countries information on international progress of software technology. Fellows, who are young scientists and engineers from developing countries, are invited to actively participate in all these projects. By doing the projects they are trained. At present, the technical focus of UNU/IIST is on formal methods for software development. UNU/IIST is an internationally recognised center in the area of formal methods. However, no software technique is universally applicable. We are prepared to choose complementary techniques for our projects, if necessary. UNU/IIST produces a report series. Reports are either Research R , Technical T , Compendia C or Administrative A. They are records of UNU/IIST activities and research and development achievements. Many of the reports are also published in conference proceedings and journals. Abstract We formalise the semantics of V ? , a simple version of Verilog hardware description language using an extension of Duration Calculus. The language is simple enough for experimenting formalisation, but contains suucient features for being practically relevant. V ? programs can exhibit a rich variety of computations, and it is therefore necessary to extend Duration Calculus with several features, including Weakly Monotonic Time, innnite intervals and xed point operators. The semantics is compositional and can be used as the formal basis of a formal theory of Verilog.