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Lecture Software engineering (9/e): Chapter 20 - Sommerville

Chapter 20- Embedded systems. The objective of this chapter is to introduce some of the characteristic features of embedded real-time systems and real-time software engineering. When you have read this chapter, you will: understand the concept of embedded software, which is used to control systems that must react to external events in their environment; have been introduced to a design process for real-time systems, where the software systems are organized as a set of cooperating processes. | Chapter 20- Embedded Systems Lecture 1 Topics covered Embedded systems design Architectural patterns Timing analysis Real-time operating systems Embedded software Computers are used to control a wide range of systems from simple domestic machines, through games controllers, to entire manufacturing plants. Their software must react to events generated by the hardware and, often, issue control signals in response to these events. The software in these systems is embedded in system hardware, often in read-only memory, and usually responds, in real time, to events from the system’s environment. Responsiveness Responsiveness in real-time is the critical difference between embedded systems and other software systems, such as information systems, web-based systems or personal software systems. For non-real-time systems, correctness can be defined by specifying how system inputs map to corresponding outputs that should be produced by the system. In a real-time system, the correctness depends | Chapter 20- Embedded Systems Lecture 1 Topics covered Embedded systems design Architectural patterns Timing analysis Real-time operating systems Embedded software Computers are used to control a wide range of systems from simple domestic machines, through games controllers, to entire manufacturing plants. Their software must react to events generated by the hardware and, often, issue control signals in response to these events. The software in these systems is embedded in system hardware, often in read-only memory, and usually responds, in real time, to events from the system’s environment. Responsiveness Responsiveness in real-time is the critical difference between embedded systems and other software systems, such as information systems, web-based systems or personal software systems. For non-real-time systems, correctness can be defined by specifying how system inputs map to corresponding outputs that should be produced by the system. In a real-time system, the correctness depends both on the response to an input and the time taken to generate that response. If the system takes too long to respond, then the required response may be ineffective. Definition A real-time system is a software system where the correct functioning of the system depends on the results produced by the system and the time at which these results are produced. A soft real-time system is a system whose operation is degraded if results are not produced according to the specified timing requirements. A hard real-time system is a system whose operation is incorrect if results are not produced according to the timing specification. Embedded system characteristics Embedded systems generally run continuously and do not terminate. Interactions with the system’s environment are uncontrollable and unpredictable. There may be physical limitations (e.g. power) that affect the design of a system. Direct hardware interaction may be necessary. Issues of safety and reliability may dominate the system .