Components & Characteristics of an Embedded System Embedded Operating System Application Areas of Embedded d Systems Automotive Industrial Automation Building Automation etc. 1 2 Embedded System Components Hardware Software Time operation 3 HARDWARE Processor Memory Timers Communication ports Power Supply SOFTWARE Availability of System Memory Availability of processor speed The need to limit power dissipation when wait the events, run, stop and wake up REAL TIME OPERATING SYSTEM (RTOS) Supervises the application software and provides a mechanism to let the processor run a process as per scheduling an do the switching from one process (task) to another process. 4
sensors i/p actuators o/p Microcontroller / DSP : monitors and controls the environment Sensors : collects data from environment through input devices Actuators : displays system s s status through output devices Timer : provides response within a certain time frame Important Characteristics of embedded system Embedded Systems are designed to do some specific task i.e., it is not a general purpose kind of a system. Software (Firmware) for Embedded Systems are stored in ROM or flash memory. Knowledge about behavior at design time can be used to minimize resources and to maximize robustness. 5 6 STANDALONE EMBEDDED SYSTEM REAL TIME EMBEDDED SYSTEM NETWORK APPLIANCES MOBILE EMBEDDED SYSTEM It is built using a specialized A real time embedded system communication processor, ll i h i memory a number of network installed. tlld This kind of system is access interfaces (known as network ports), and special request. Examples of real time software that implements logic embedded systems are aircraft for sending information from one device to another device. usually monitors the environment where the embedded system is required to respond in time to a engine control systems, nuclear monitoring systems and medical monitoring equipment. Network appliances are a new class of embedded systems that in addition to traditional real time processing must support a broad and changing array of network protocols. Mobile Embedded Systems usually are simple, battery powered systems with resource limitations. In some situations, their batteries lifetime becomes a prim issue. 7 8
capture input signals and process the data control peripheral circuitry network with other ES s or computers e.g. sensor arrays in forest canopy both fixed and ad-hoc networks user interfacing i data storage An embedded operating system (EOS) is a system software that manages all the other programs and devices in an embedded bddd system. It also normally has boot loader, OS kernel, required device drivers, file systems for the user data and so forth. embedded operating systems deals with task switching, scheduling of tasks, memory allocation, etc. 9 10 Single Functioned Usually executes a specific program repeatedly Tightly hl Constrained All computing systems have constraints on design metrics, but those on embedded systems can be especially tight. A design metric is a measure of an implementation s features, such as cost, size, performance and power. Secondary Memory Generally embedded system doesn t need secondary memory. Reactive and Real Time Many embedded systems must continually react to changes in the system s s environment and must compute certain results in real time without delay. Unlike a desktop computer system which may have new software loaded onto it frequently, embedded bddd systems retain the same code for a long time, sometimes indefinitely. Do not usually include support for external storage or graphical interfaces 11 12
VxWroks, RTLinux, OS 9 Windows, Palm OS, Linux, Android Real Time Operating Systems (RTOS) Guarantee responses time to each event Mainly used by time critical applications Non Real Time Operating Systems Not guarantee defined response times Mostly used if multiple applications are needed Single System Control Loop Such systems run a single task. Multitasking Operating System In a multitasking operating system, several tasks or processes appear to execute concurrently. Preemptive Operating System A preemptive operating system is a multitasking operating system that defines preemptive priorities for tasks. A higher priority task always interrupts and is always run before a lower priority task. Rate Monotonic Operating System Such operating system guarantees that tasks in the system can run at a certain interval of time for a certain period of time. When this guarantee is not met, the system software can be notified of failure and take appropriate action. Constant Time Operations Constant time operations are the cornerstone of real time responsiveness and predictable capacity loading. 13 14 Interrupt Response Times Embedded Operating Systems normally provide for fast interrupt response times by separating interrupt handlers in two phases. Priority Inversion Priority inversion is a condition in preemptive operating systems where a lower priority task claims a resource that is subsequently required by a higher priority task. Monolithic Operating Systems A monolithic operating system includes all operating system code such as device drivers and file system handlers as part of a single system image. Micro Kernels A micro kernel operating system stem includes only the bare necessities such as task switching, scheduling and device handling interfaces in the operating system code. 15 Sukriti Jalali, Trends and Implications in Embedded Systems Development, Tata Consultancy Services Limited, 2009 16
car electronics systems Infotainment/Telematics Electronic subsystems devoted to information processing, communication with outside world and entertainment. The main features are wide-band, adaptive realtime (ART) constraints, non-critical Power train/chassis Mi Main features are hard real-time lti constraints, t safety critical, fault tl tolerant, t low band (e.g. engine, brakes, steering), with subsystems being isolated from one another mostly for historical reasons Cabin Mi Main features are real-time and non-critical i (e.g., power windows, air conditioning). i i 17 18 Today s car real-time and safety-critical electronics systems are implemented over distributed architectures that generally include: Several Electronic Control Units (ECU s) communicating via: one or more (for fault tolerant systems) networked broadcast buses controlled by communication protocols (e.g. CAN, TTP, LIN, and Flex Ray) ECU Application and diagnostic software System software (e.g., RTOS and Communication layers); One or more micro-controllers with local memories and communication controller(s) with one or multiple channels to support redundancy for fault tolerant systems and complex bus architectures such as constellations o s and star couplers; (Optional) Dual ported RAM s for: Communications between bus controllers and micro-controllers within the same ECU. Communications between CPU s within the same ECU. 19 20
Industrial automation is applied to control and optimize production processes and to provide high-quality and reliable products and services by minimizing i i i material, cost and energy waste. Examples traffic control, chemical process control, distributed ib t d production control, machine and plant control (e.g. hydraulic presses, machine tools with several synchronized axles, coupled robots), and agentbased manufacturing. 21 22 Automation systems rely on smart sensors, actuators and other industrial equipment like robotic and mechatronics components. The standard architecture consists of PLCs (Programmable Logic Controllers) or DCS (Distributed Control Systems), field bus systems, and PCs as man machine interfaces as well as intelligent sensor and actuators t (e.g. frequency converters). The field bus systems gather the signals from process level or the sensors/actuators ators with field bus interfaces and are directly connected to distributed or centralized control devices (e.g. PLCs). In Europe Siemens is the market leader in PLCs (Simatic S7) and an important supplier of DCS systems (PCS7) as well as CNC (Computerized Numerical Control) equipment. 23 24
Building automation is concerned with monitoring and control of building services equipment. 25 26 27 28
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