17,078 research outputs found

    Hierarchical gate-level verification of speed-independent circuits

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    This paper presents a method for the verification of speed-independent circuits. The main contribution is the reduction of the circuit to a set of complex gates that makes the verification time complexity depend only on the number of state signals (C elements, RS flip-flops) of the circuit. Despite the reduction to complex gates, verification is kept exact. The specification of the environment only requires to describe the transitions of the input/output signals of the circuit and is allowed to express choice and non-determinism. Experimental results obtained from circuits with more than 500 gates show that the computational cost can be drastically reduced when using hierarchical verification.Peer ReviewedPostprint (published version

    Realizing burstmode circuits via STG speed independent synthesis

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    Journal ArticleThis report discusses the similarities and differences of STG and Burstmode specifications and synthesis methods. The first part of the report examines the applicability and efficiency of STG's single controller fork-join concurrency ability versus Burstmode's partitioned fork-join concurrency approach. Results comparing the synthesis results for designs using the same level of concurrency in the controllers (STG and Burstmode), as well as the different methods of realizing fork-join concurrency, are presented. The second part compares the timing assumptions being made by the SI synthesis algorithms and if they can generate a hazard-free solution under Burstmode burst property and fundamental mode assumptions. This comparison shows that speed independent generalized C-element implementations exhibit hazards under the burst property assumption model and can thus not be used to implement Burstmode controllers. It also shows that the SI standard C-element approach, while complying with the burst property of a legal Burstmode specification, may not generate - from a Burstmode point of view - minimum covers. In addition, timed circuits are analyzed for the same hazard considerations. Timed circuits have the same problems as SI when it comes to Burstmode hazard considerations. An extension to timed circuit synthesis that potentially can reduce the number of entrance violations in a standard C-element implementation significantly is also presented

    A new look at the conditions for the synthesis of speed-independent circuits

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    This paper presents a set of sufficient conditions for the gate-level synthesis of speed-independent circuits when constrained to a given class of gate library. Existing synthesis methodologies are restricted to architectures that use simple AND-gates, and do not exploit the advantages offered by the existence of complex gates. The use of complex gates increases the speed and reduces the area of the circuits. These improvements are achieved because of (1) the elimination of the distributivity, signal persistency and unique minimal state requirements imposed by other techniques; (2) the reduction in the number of internal signals necessary to guarantee the synthesis; and finally (3) the utilization of optimization techniques to reduce the fan-in of the involved gates and the number of required memory elements.Peer ReviewedPostprint (published version

    Asynchronous techniques for system-on-chip design

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    SoC design will require asynchronous techniques as the large parameter variations across the chip will make it impossible to control delays in clock networks and other global signals efficiently. Initially, SoCs will be globally asynchronous and locally synchronous (GALS). But the complexity of the numerous asynchronous/synchronous interfaces required in a GALS will eventually lead to entirely asynchronous solutions. This paper introduces the main design principles, methods, and building blocks for asynchronous VLSI systems, with an emphasis on communication and synchronization. Asynchronous circuits with the only delay assumption of isochronic forks are called quasi-delay-insensitive (QDI). QDI is used in the paper as the basis for asynchronous logic. The paper discusses asynchronous handshake protocols for communication and the notion of validity/neutrality tests, and completion tree. Basic building blocks for sequencing, storage, function evaluation, and buses are described, and two alternative methods for the implementation of an arbitrary computation are explained. Issues of arbitration, and synchronization play an important role in complex distributed systems and especially in GALS. The two main asynchronous/synchronous interfaces needed in GALS-one based on synchronizer, the other on stoppable clock-are described and analyzed

    Covering conditions and algorithms for the synthesis of speed-independent circuits

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    Journal ArticleAbstract-This paper presents theory and algorithms for the synthesis of standard C-implementations of speed-independent circuits. These implementations are block-level circuits which may consist of atomic gates to perform complex functions in order to ensure hazard freedom. First, we present Boolean covering conditions that guarantee that the standard C-implementations operate correctly. Then, we present two algorithms that produce optimal solutions to the covering problem. The first algorithm is always applicable, but does not complete on large circuits. The second algorithm, motivated by our observation that our covering problem can often be solved with a single cube, finds the optimal single-cube solution when such a solution exists. When applicable, the second algorithm is dramatically more efficient than the first, more general algorithm. We present results for benchmark specifications which indicate that our single-cube algorithm is applicable on most benchmark circuits and reduces run times by over an order of magnitude. The block-level circuits generated by our algorithms are a good starting point for tools that perform technology mapping to obtain gate-level speed independent circuits

    Efficient verification of hazard-freedom in gate-level timed asynchronous circuits

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    Journal ArticleAbstract-This paper presents an efficient method for verifying hazard-freedom in gate-level timed asynchronous circuits. Timed circuits are a class of asynchronous circuits that are optimized using explicit timing information. In asynchronous circuits, correct operation requires that there are no hazards in the circuit implementation. Therefore, when designing an asynchronous circuit, each internal node and output of the circuit must be verified for hazard-freedom to ensure correct operation. Current verification algorithms for timed circuits require an explicit state exploration that often results in state explosion for even modest-sized examples. The goal of this paper is to abstract the behavior of internal nodes and utilize this information to make a conservative determination of hazard-freedom for each node in the circuit. Experimental results indicate that this approach is substantially more efficient than existing timing verification tools. These results also indicate that this method scales well for large examples that could not be previously analyzed, in that it is capable of analyzing these circuits in less than a second. While this method is conservative in that some false hazards may be reported, our results indicate that their number is small

    Achieving fast and exact hazard-free logic minimization of extended burst-mode gC finite state machines

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    Journal ArticleAbstract This paper presents a new approach to two-level hazard-free logic minimization in the context of extended burst-mode finite state machine synthesis targeting generalized C-elements (gC). No currently available minimizers for literal-exact two-level hazard-free logic minimization of extended burst-mode gC controllers can handle large circuits without synthesis times ranging up over thousands of seconds. Even existing heuristic approaches take too much time when iterative exploration over a large design space is required and do not yield minimum results. The logic minimization approach presented in this paper is based on state graph exploration in conjunction with single-cube cover algorithms, an approach that has not been considered for minimization of extended burst-mode finite state machines previously. Our algorithm achieves very fast logic minimization by introducing compacted state graphs and cover tables and an efficient single-cube cover algorithm for single-output minimization. Our exact logic minimizer finds minimal number of literal solutions to all currently available benchmarks, in less than one second on a 333 MHz microprocessor - more than three orders of magnitude faster than existing literal exact methods, and over an order of magnitude faster than existing heuristic methods for the largest benchmarks. This includes a benchmark that has never been possible to solve exactly in number of literals before

    Safety considerations in the design and operation of large wind turbines

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    The engineering and safety techniques used to assure the reliable and safe operation of large wind turbine generators utilizing the Mod 2 Wind Turbine System Program as an example is described. The techniques involve a careful definition of the wind turbine's natural and operating environments, use of proven structural design criteria and analysis techniques, an evaluation of potential failure modes and hazards, and use of a fail safe and redundant component engineering philosophy. The role of an effective quality assurance program, tailored to specific hardware criticality, and the checkout and validation program developed to assure system integrity are described

    Technology mapping of timed circuits

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    Journal ArticleAbstract This paper presents an automated procedure for the technology mapping of timed circuits to practical gate libraries. Timed circuits are a class of asynchronous circuits that incorporate explicit timing information in the specification which is used throughout the design process to optimize the implementation. Our procedure begins with a timed specification and a delay-annotated gate library description which must include 2-input AND gates, OR gates, and C-elements, but optionally can include higher-fanin gates, AND-OR-INVERT blocks, and generalized C-elements. Our procedure first generates a technology-independent timed circuit netlist composed of possibly high-fanin AND gates, OR gates, and 2-input Celements. The procedure then investigates simultaneous decompositions of all high-fanin gates by adding state variables to the the specfication and performing resyn-thesis. Although multiple decompositions are explored, timing information is utilized to significantly reduce their number. Once all gates are sufficiently decomposed, the netlist can be mapped to the given gate library, taking advantage of any compact complex gates available. The decomposition and resyn-thesis steps have been fully automated within the synthesis tool ATACS and we present results for several examples
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