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The Time-Triggered Architecture (TTA) and its software development environment for the Time-Triggered Protocol (TTP) provide a framework which allows the efficient development of distributed embedded applications. Separate development of system architecture and subsystems design, strict control of key system interfaces and separation of functional/logical from temporal behavior facilitate the reuse and seamless integration of electronic subsystems provided by different suppliers. TTA is an integrated platform solution which allows modular application development and certification up to the highest criticality classes with reuse of components. TTA principles improve the ability of system designers to significantly reduce system integration effort and obsolescence management costs. The time-triggered communication protocol TTP provides high performance and fault tolerance for the data transfer between distributed applications.

The increasing complexity of distributed embedded systems, as found today in airplanes or cars, becomes more and more a critical cost-factor for their development. Model-based approaches have recently demonstrated their potential for both improving and accelerating (software) development processes. Therefore, in the project DECOS1, which aims at improving system architectures and development of distributed safety-critical embedded systems, an integrated, model-driven tool-chain is established, accompanying the system development process from design to deployment. This paper gives an overview of this tool-chain and outlines important design decisions and features.

Development and verification of systems for internal aircraft networks include multiple software layers. These layers are mainly the application-specific components, communication layers, redundancy management and other system services. Verification of these system layers in the early stages of the design process, before a physical network is available, and during the design process has become a critical need in order to reduce design costs and project risks. Time-Triggered Architectures (TTA) and SCADE are both well-established technologies and tools for building safety-critical embedded systems. Both are based on the synchronous paradigm; TTA for the communication infrastructure and distributed embedded computing, and SCADE for simulating and generating code for the application components.

The paper presents a communication architecture for distributed embedded computer systems that require to transmit safety-critical real-time data - which must not be delayed - on the same bus as non-critical data. Such non-critical data can come from sources like sensors and event-based traffic, typically for on-demand diagnosis. This architecture utilizes the communication protocols TTP/C and TTP/A, and a software layer in the distributed nodes, to provide a fault-tolerant platform for reliable yet flexible communication over a multiplex bus.

The next generation of cars will consist of a high number of networked electronic control units (ECUs) and significantly more complex software modules and control applications than today's models. Besides applications like engine control, air condition control and anti-theft systems, which are already available in today's cars, the first steps towards the introduction of safety-relevant steer-by-wire and brake-by-wire systems will be undertaken. Additionally, the demand for in-car entertainment and information systems (e.g. Internet terminals, video-streaming applications) will also increase. Since all these systems have conflicting requirements to the underlying network protocol (latency, predictability, throughput…), the straight-forward way would be to use autonomous busses and networks for every kind of distributed system within the car body (ultra-available safety-relevant systems, non-safety-relevant control systems, entertainment and media systems).

The Time-Triggered Architecture (TTA) is a technology that is especially well suited for the design and implementation of ‘by-wire’ systems with demanding real-time and safety requirements. Design and prototyping require thorough planning. New hardware and software support simulation and prototyping of distributed real-time systems, easing the implementation of by-wire applications. Integrated tools support the whole design process from system setup to simulation and application programming. The paper describes a by-wire prototype design process based on the TTA and a currently available development environment.

This paper presents the software certification activities carried out on TTP-OS to make this hard real-time, fault-tolerant operating system available for safety-critical applications in the automotive and aerospace industries requiring certification. The steps and measures, while specifically tailored to make an RTOS certifiable, were defined in accordance with the RTCA/DO-178B [1] guideline. The major single goal of these activities is to achieve traceability of requirements. Requirements are traced from the Software Requirements Document all the way down through the software lifecycle to the test-cases ensure consistency and accuracy of a mature software development approach. The steps and milestones along the lifecycle are described, offering an insight into the software certification efforts required.