The most visible use of computers and software is processing information for human consumption. The vast majority of computers in use, however, are much less visible. They run the engine, brakes, seatbelts, airbag, and audio system in your car. They digitally encode your voice and construct a radio signal to send it from your cell phone to a base station. They command robots on a factory floor, power generation in a power plant, processes in a chemical plant, and traffic lights in a city. These less visible computers are called embedded systems, and the software they run is called embedded software. The principal challenges in designing and analyzing embedded systems stem from their interaction with physical processes. This book takes a cyber-physical approach to embedded systems, introducing the engineering concepts underlying embedded systems as a technology and as a subject of study. The focus is on modeling, design, and analysis of cyber-physical systems, which integrate computation, networking, and physical processes. The second edition offers two new chapters, several new exercises, and other improvements. The book can be used as a textbook at the advanced undergraduate or introductory graduate level and as a professional reference for practicing engineers and computer scientists. Readers should have some familiarity with machine structures, computer programming, basic discrete mathematics and algorithms, and signals and systems.

Introduction to Embedded Systems - A Cyber-Physical Systems Approach

The Time-Triggered Architecture (TTA) is a computer architecture for distributed real-time systems in safety critical applications, such as computer controlled brakes, or computer assisted steering in an automobile. The TTA is a composable architecture for the design of large real-time systems. Its main characteristics are a common notion of time in all subsystems of the architecture and the provision of fully specified interfaces, called temporal firewalls, between these subsystems. This paper gives an overview of the TTA, discusses the architectural principles, describes the sensor/actuator interfaces in the TTA and informs about the implementation of fault-tolerance in the TTA.

The time-triggered architecture

Until the late eighties, information processing was associated with large mainframe computers and huge tape drives. During the nineties, this trend shifted towards information processing with personal computers, or PCs. The trend towards miniaturization continues. In the future, most of the information processing systems will be quite small and embedded into larger products such as transportation and fabrication equipment. Hence, these kinds of systems are called embedded systems. It is expected that the total market volume of embedded systems will be significantly larger than that of traditional information processing systems such as PCs and mainframes. Embedded systems share a number of common characteristics. For example, they must be dependable, efficient, meet real-time constraints and require customized user interfaces (instead of generic keyboard and mouse interfaces). Therefore, it makes sense to consider common principles of embedded system design. Embedded System Design starts with an introduction into the area and a survey of specification languages for embedded systems.A brief overview is provided of hardware devices used for embedded systems and also presents the essentials of software design for embedded systems. Real-time operating systems and real-time scheduling are covered briefly.Techniques for implementing embedded systems are also discussed, using hardware/software codesign. It closes with a survey on validation techniques. Embedded System Designcan be used as a text book for courses on embedded systems and as a source which provides pointers to relevant material in the area for PhD students and teachers. The book assumes a basic knowledge of information processing hardware and software.

Embedded System Design

The requirement for flexible operation is becoming increasingly important in modern industrial systems. This requirement has to be supported at all system levels, including the field level in process industry, as well as the cell and machine control levels in manufacturing industry, where fieldbus-based communication systems are commonly found. Furthermore, typical applications at these levels require both time- and event-triggered communication services, in most cases under stringent timing constraints, to convey state data in the former case and alarms and management data in the latter. However, neither the requirement for flexible operation under guaranteed timeliness nor for joint support of time and event-triggered traffic are efficiently fulfilled by most of existing fieldbus systems. This paper presents a new protocol, flexible time-triggered communication on controller area network, which fulfills both requirements: it supports time-triggered communication in a flexible way as well as being an efficient combination of both time- and event-triggered traffic with temporal isolation. These types of traffic are handled by two complementary subsystems, the synchronous and the asynchronous messaging systems, respectively. The paper includes a justification for the new protocol as well as its description and worst case temporal analysis for both subsystems. This analysis shows the capability of the protocol to convey real-time traffic of either type.

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The FTT-CAN protocol: why and how

Automated aircraft control has traditionally been divided into distinct "functions" that are implemented separately (eg, autopilot, autothrottle, flight management); each function has its own fault-tolerant computer system, and dependencies among different functions are generally limited to the exchange of sensor and control data A by-product of this "federated" architecture is that faults are strongly contained within the computer system of the function where they occur and cannot readily propagate to affect the operation of other functions More modern avionics architectures contemplate supporting multiple functions on a single, shared, fault-tolerant computer system where natural fault containment boundaries are less sharply defined Partitioning uses appropriate hardware and software mechanisms to restore strong fault containment to such integrated architectures This report examines the requirements for partitioning, mechanisms for their realization, and issues in providing assurance for partitioning Because partitioning shares some concerns with computer security, security models are reviewed and compared with the concerns of partitioning

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Partitioning in Avionics Architectures: Requirements, Mechanisms, and Assurance

The Time-Triggered Protocol integrates such services as predictable message transmission, clock synchronization, membership, mode change, and blackout handling. It also supports replicated nodes and replicated communication channels. The authors describe their architectural assumptions, fault hypothesis, and objectives for the TTP protocol. After they elaborate on its rationale, they give a detailed protocol description. They also discuss TTP characteristics and compare its performance with that of other protocols proposed for control applications. >

G. Grunsteidl

Papers

TTP/spl minus/a protocol for fault-tolerant real-time systems