Learn More
Traditionally, circuits with combinational loops are found only in asynchronous designs. However, combinational loops can also be useful for synchronous circuit design. Combinational loops can arise from high-level language behavioral compiling, and can be used to reduce circuit size. We provide a symbolic algorithm that detects if a sequential circuit with(More)
We present heuristic algorithms for finding a minimum BDD size cover of an incompletely specified function, assuming the variable ordering is fixed. In some algorithms based on BDDs, incompletely specified functions arise for which any cover of the function will suffice. Choosing a cover that has a small BDD representation may yield significant performance(More)
Efficient techniques for the manipulation of Binary Decision Diagrams (BDDs) are key to the success of formal verification tools. Recent advances in reachability analysis and model checking algorithms have emphasized the need for efficient algorithms for the approximation and decomposition of BDDs. In this paper we present a new algorithm for approximation(More)
We present <i>Ketchum,</i> a tool that was developed to improve the productivity of simulation-based functional verification by providing two capabilities: (1) <i>automatic test generation</i> and (2) <i>unreachability analysis.</i> Given a set of "interesting" signals in the design under test (<i>DUT</i>), automatic test generation creates input stimuli(More)
Implicit state enumeration for extended finite state machines relies on a decision procedure for Presburger arithmetic. We compare the performance of two Presburger packages, the automata-based Shasta package and the polyhedra-based Omega package. While the raw speed of each of these two packages can be superior to the other by a factor of 50 or more, we(More)
We present a state equivalence that is deened with respect to a given CTL formula. Since it does not attempt to preserve all CTL formulas, like bisimulation does, we can expect to compute coarser equivalences. We use this equivalence to manage the size of the transition relations encountered when model checking a system of interacting FSMs. Speciically, the(More)
Functional and timing verification are currently the bottlenecks in many design efforts. Simulation and emulation are extensively used for verification. Formal verification is now gaining acceptance in advanced design groups. This has been facilitated by the use of binary decision diagrams (BDDs). This paper describes the essential features of HSIS, a(More)
Computing the set of states reachable in one step from a given set of states, i.e. <i>image computation,</i> is a crucial step in several symbolic verification algorithms, including <i>model checking</i> and <i>reachability analysis.</i> So far, the best methods for quantification scheduling in image computation, with a conjunctively partitioned transition(More)