J. Plosila and K. Sere. Action systems in pipelined processor design. In Proc. of the 3rd Int. Symp. on Advanced Research in Asynchronous Circuits and Systems, pages 156 -- 166, 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....although these are not the only systems to benefit from the use of formal design. Formal methods became, thus, an increasingly important step in the design flow of digital systems. Several studies have been done in order to adapt various formalisms to the characteristics of hardware description [3, 10, 16, 18], to mention only few of them, with remarkably good results. In applying formal methods to hardware design one can distinguish two main approaches [8] post design verification and correctness preserving transformations. This study presents features of the action systems framework, formalism that ....

....the component actions are always enabled. The simplest possible synchronous system is composed of a single two phase action. System synchronization. The proposed methodology for designing synchronous action systems is built on previous work studying the development of asynchronous action systems [9, 10, 11]. Hence, the initial specification of the target system is asynchronous, of a particular structure, but quite typical for a hardware implementation targeted design. An asynchronous description is based on a master slave relation between the system and its environment [13] reflected by the req ack ....

J. Plosila and K. Sere. Action systems in pipelined processor design. In Proc. of the 3rd Int. Symp. on Advanced Research in Asynchronous Circuits and Systems, pages 156 -- 166, 1997.

....are always enabled. The simplest possible synchronous system is composed of a single two phase action. System synchronization. The design of synchronous actions systems is developed such that it takes advantage of the previous experience, concerning the development of asynchronous action systems [14, 15, 19]. The asynchronous modeling can be considered a natural way to describe system behavior. Moreover, the action systems formalism is well featured for asynchronous approach. Based on these facts, the initial specification of the target system is asynchronous. An initial asynchronous description is ....

....the initial specification of the target system is asynchronous. An initial asynchronous description is stepwise refined into a synchronous functional equivalent [16] The starting asynchronous system is, however, of a particular type, but quite typical for a hardware implementation targeted design [14, 15, 19]. The generic structure of this system is: 7 sys Async (req; ack : boolean; global variables) j[ var local variables; init initialization of variables; 1) do (req (choice 1 ; choice n ) ack : true [ req ack : false od ]j where choice j = g 1 A j 1 ) ....

J. Plosila and K. Sere. Action systems in pipelined processor design. In Proc. of the 3rd Int. Symp. on Advanced Research in Asynchronous Circuits and Systems, pages 156 -- 166, 1997.

....are part of a formal design framework, leading to correct representations. Applying the same rules to both design architectures, we will be able to delay the decision upon the final device architecture. The action systems formalism has recently been adapted to asynchronous circuit design [10]. The main purpose of this study is thus, to extend the action systems framework with concepts needed in modeling synchronous circuits. Our approach is based on a two phase modelling. It allows us to model real parallel execution, even when actions interfere. The resulting systems are called ....

J. Plosila and K. Sere. Action systems in pipelined processor design. In Proc. of the 3rd Int. Symp. on Advanced Research in Asynchronous Circuits and Systems, pages 156 -- 166, 1997.

....the design process yields a logically highly reliable implementation. In this paper, the emphasis is on the implementation itself rather than in the details of the derivation. Basically, the derivation flow follows the guidelines presented in our previous work on a pipelined microprocessor [13]. We thereby provide more evidence that our approach is suitable for asynchronous design. The resulting circuit contains a 46 word program ROM (PROM) for the involved algorithms and a 2 stage pipeline. The control logic is mainly speed independent, but the data path completion signals for ....

....include assignment, sequential composition, assertion, conditional choice and iteration, and are defined using weakest precondition predicate transformers. Comprehensive study on this formalism can be found for example in [2, 3] The action systems framework in asynchronous design is treated in [13, 14, 15]. Actions An action is a guarded command of the form g S where g, the guard, is a boolean condition, and S, the body, is any statement in our language. The action A is said to be enabled when the guard is true, disabled otherwise. If g is invariantly true, we often write the action A simply ....

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J. Plosila and K. Sere. Action systems in pipelined processor design. In Proc. of the 3rd Int. Symp. on Advanced Research in Asynchronous Circuits and Systems, pages 156 -- 166, 1997.

....the logical correctness of digital hardware. These methods are especially well suited for modeling asynchronous self timed behavior, where sequencing of events is based on handshakes between units [11] Also the action systems formalism has recently been adapted to asynchronous circuit design [17, 18, 19, 20]. However, the majority of modern digital hardware still uses synchronous techniques. The purpose of this paper is to extend the action systems framework with concepts needed in modeling synchronous circuits. The operation of a synchronous device is based on storage elements sensitive to the ....

J. Plosila and K. Sere. Action systems in pipelined processor design. In Proc. of the 3rd Int. Symp. on Advanced Research in Asynchronous Circuits and Systems, pages 156 -- 166, 1997.

....into their synchronous representation within the refinement calculus. We might call this subset as a synchronous implementable class of descriptions. Most of the asynchronous data processing action systems can be refined to this generic format we take into account, as previous work proves it [15, 16, 17, 18]. We also provided immediate schematic representation for the constructs we analyzed. The example studied in Section 6 is an illustration of the presented design methodology. Either by custom design or automated means, the whole design process, from the abstract asynchronous specification to the ....

J. Plosila and K. Sere. Action systems in pipelined processor design. In Proc. of the 3rd Int. Symp. on Advanced Research in Asynchronous Circuits and Systems, pages 156 -- 166, 1997.

....the circuit. The program is then compiled, manually or automatically, into a circuit by applying correctness preserving program transformations. Hence, the obtained circuit is logically correct by construction. The method has been successfully applied to the design of several non trivial circuits [3, 18, 19]. Action systems, like many other similar formal methods, still lack good tool support or the methods and tools that are available have not been well integrated with the current engineering practice. An approach that has 1 been accepted by many industrial organisations is the B Method and its ....

J. Plosila and K. Sere. Action Systems in Pipelined Processor Design. In Proc. of the Third International Symposium on Advanced Research in Asynchronous Circuits, April 1997. IEEE Computer Society Press. 31

....has showed that formal techniques familiar from parallel programming are usable for circuit design as well. Action systems have shown their strength in the construction of parallel and distributed systems [1, 3] Their suitability in the initial steps of circuit design has also been demonstrated [2, 16]. In this paper, we show how action systems are used to model delayinsensitive circuits. We define a class of action systems, quasi delay insensitive action systems, by restricting the way the actions in a system interact with each other. A computation of such an action system models a computation ....

J. Plosila and K. Sere. Action Systems in Pipelined Processor Design. Technical Report 54, Turku Centre for Computer Science, 1996. Available from http://www.tucs.abo.fi/publications/techreports/TR54.ps.gz.

....components. A master system is the active party it sends a signal, whereas a server is the passive party it receives a signal. Each master can be a server of some other system, and, respectively, each server system can be a master of some other system at the same time. We have shown [20, 3] how arbitrary action systems are decomposed into a parallel composition of action systems, master server pairs, where each component system models some functional entity of the target circuit. In this section we only give a generic pattern of such decomposition. Each component is then stepwise ....

J. Plosila and K. Sere. Action Systems in Pipelined Processor Design. In Proc. of the 3rd International Symposium on Advanced Research in Asynchronous Circuits and Systems, Eindhoven, The Netherlands, April 1997. IEEE Computer Society Press, 1997.

....prove the correctness of the handshaking expansion. The proof is carried out within the Refinement Calculus for action systems. Action systems have shown their strength in the construction of parallel and distributed systems [3, 5] as well as in the initial steps of asynchronous circuit design [4, 16]. In an accompanying paper, Plosila et al. 15] propose a method to synthesize delay insensitive circuits from high level action system specifications. Action systems are similar to UNITY programs [8] that have an associated temporal logic as a specification language. The design and reasoning ....

J. Plosila and K. Sere. Action Systems in Pipelined Processor Design. Technical Report 54, Turku Centre for Computer Science, 1996. Available from http://www.tucs.abo.fi/publications/techreports/TR54.ps.gz.

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