Understanding designers' intentions and accurately verifying a design are major obstacles for verification engineers today. Currently available debugging tools, such as waveform viewers, are unwieldy, often requiring the user to search through millions of cycles of logic simulation data to locate a problem. In this paper, we present Inferno, a novel solution capable of automatically extracting semantic information from a design's interface from simulation information. The semantic structure of an interface's communication protocol is presented to the user as a set of transactions, that is, monolithic communication units that have typically been observed several times during the logic simulation. Transactions can graphically be presented to the user and used as an aid to understand and validate the communication protocol of a design's interface. In addition, approved transactions can also be encoded as assertions expressed in a hardware description language (HDL) and used in constrained-random simulation to certify that the interface protocol adheres to the set of observed (and user-approved) transactions. Moreover, we developed a new closed-loop verification methodology based on Inferno, called transactional verification, which leverages approved transactions to describe correct design behavior. In our methodology, transactions are concurrently extracted during a constraint-based random simulation: the anomalous ones are flagged as potentially buggy and presented to the user for inspection. In the experimental results, we evaluate the performance and the quality of the results of Inferno on a broad range of testbench designs and several of their interfaces, including a number of communication intellectual properties and the OpenSPARC T1 8-core processor from Sun.

Assessing the correctness of a digital design is a challenging task hampered by extremely large circuit netlists, counterintuitive property descriptions and ill-defined specifications. In this paper we propose a new verification methodology, inspired by the principle of least astonishment. The underlying idea is to provide an automatic assessment of what constitutes "common behavior" for a system, and use this to detect any anomaly in the design. Deviant behavior is presented to the verification engineer through intuitive, compact diagrams which lend themselves to quick inspection for correctness. To enable this methodology we introduce Inferno, a new tool which can analyze the results of a logic simulation trace and automatically extract high-level diagrams representing the design's transaction activity across any user-defined interface. In addition, Inferno can automatically generate a checker module corresponding to a given transaction, suitable for use in a wide range of verification methodologies. We envision the deployment of Inferno in a closed-loop constraint-random simulation methodology where any new transaction detected on the interface is presented to the user for analysis and, once deemed legal, it is merged into an "approved transactions" checker, which flags the detection of any new type of transactions. We provide a series of examples and experimental results to show the effectiveness of Inferno and some of its possible uses.