EMBEDDED COMPUTER SYSTEMS are now everywhere: from alarm clocks to PDAs, from mobile phones to cars, almost all the devices we use are controlled by embedded computer systems. An important class of embedded computer systems is that of real-time systems, which have to fulfill strict timing requirements. As realtime systems become more complex, they are often implemented using distributed heterogeneous architectures. The main objective of this thesis is to develop analysis and synthesis methods for communication-intensive heterogeneous hard real-time systems. The systems are heterogeneous not only in terms of platforms and communication protocols, but also in terms of scheduling policies. Regarding this last aspect, in this thesis we consider time-driven systems, event-driven systems, and a combination of both, called multi-cluster systems. The analysis takes into

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In order to represent efficiently large systems, a mechanism for hierarchical composition is needed so that the model may be constructed in a structured manner and composed of simpler units easily comprehensible by the designer at each description level. In this paper we formally define the notion of hierarchy for a Petri net based representation used for modeling embedded systems. We show how small parts of a large system may be transformed by using the concept of hierarchy and the advantages of a transformational approach in the verification of embedded systems. A real-life example illustrates the feasibility of our approach on practical applications.

In this paper, we present a virtual integration platform based design methodology for distributed automotive systems. The platform, built within the `Virtual Component Co-Design' tool (VCC), provides the ability of distributing a given system functionality over an architecture so as to validate different solutions in terms of cost, safety requirements, and real-time constraints. The virtual platform constitutes the foundation for design decisions early in the development phase, therefore enabling decisive and competitive advantages in the development process. This paper focuses on one of the key-enablers of the methodology, the Universal Communication Model (UCM). The UCM is defined at a level of abstraction that allows accurate estimates of the performance including the latencies over the bus network, and good simulation performance. In addition, due to the high level of reusability and parameterization of its components, it can be used as a framework for modeling the different communication protocols common in the automotive domain.

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Design of embedded systems is a complex task that requires design cycles founded upon formal notation, so that the synthesis from specification to implementation can be carried out systematically. In this paper we present a computational model for embedded systems based on Petri nets called PRES+. It includes an explicit notion of time and allows a concise formulation of models. Tokens, in our notation, hold information and transitions---when fired--- perform transformation of data. Based on this model we define several notions of equivalence (reachable, behavioral, time, and total), which provide the framework for transformational synthesis of embedded systems. Different representations of an Ethernet network coprocessor are studied in order to illustrate the applicability of PRES+ and the definitions of equivalence on practical systems.

We present the EWD design environment and methodology, a modeling and simulation framework suited for complex and heterogeneous embedded systems with varying degrees of expressibility and modeling fidelity. This environment promotes the use of multiple models of computation (MoCs) to support heterogeneity and metamodeling for conformance tests of syntactic and static semantics during the process of modeling. Therefore, EWD is a multiple MoC modeling and simulation framework that ensures conformance of the MoC formalisms during model construction using a metamodeling approach. In addition, EWD provides a suite of translation tools that generate executable models for two simulation frameworks to demonstrate its language-independent modeling framework. The EWD methodology uses the Generic Modeling Environment for customization of the MoC-specific modeling syntax into a visual representation. To embed the execution semantics of the MoCs into the models, we have built parsing and translation tools that leverage an XML-based interoperability language. This interoperability language is then translated into executable Standard ML or Haskell models that can also be analyzed by existing simulation frameworks such as SML-Sys or ForSyDe. In summary, EWD is a metamodeling driven multitarget design environment with multi-MoC modeling capability.

FACULTY OF ENGINEERING ELECTRONICS AND COMPUTER SCIENCE DEPARTMENT MPhil/PhD Transfer Report Mixed Control/Data-Flow Representation for Modelling and Verification of Embedded Systems by Mauricio Varea Embedded system design issues become critical as implementation technologies evolve. The interaction between the control and data flow of an embedded system specification is an important consideration and, in order to cope with this aspect, a new internal design representation called Dual Flow Net (DFN) is introduced and further analysed in this thesis. One of the key features of this internal representation is its tight control and data flow interaction, which is achieved by means of two new concepts. Firstly, the structure of the new DFN model is formulated employing a tripartite graph as basis, which turns out to be advantageous for modelling heterogeneous systems. Secondly, a complex domain marking scheme is used to describe the behaviour of the system, leading to better results in terms of modelling the dynamics of the embedded system specification. Structural definitions, behavioural rules and graphical representation of the new DFN model is presented in this work.

EMBEDDED SYSTEMS are used in a wide spectrum of applications ranging from home appliances and mobile devices to medical equipment and vehicle controllers. They are typically characterized by their real-time behavior and many of them must fulfill strict requirements on reliability and correctness.

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