Embedded Operating System

According to IEEE (Institute of Electrical and Electronics Engineers) of the definition, embedded system is a "control, monitor or assistive devices, machines and equipment to run the device" (devices used to control, monitor, or assist the operation of equipment, machinery or plants) . Can be seen from the embedded system is a complex software and hardware, you can also cover the machinery and other ancillary devices. Embedded systems are closely integrated with the application of highly specialized nature of the actual system needs to be combined with a reasonable reduction of use. A generally accepted national definition: application-centric, computer technology, software and hardware can be cut to meet the application system functionality, reliability, cost, size, power demanding a dedicated computer system.HistoryIn fact, long ago, embedded this concept has been in existence. In communications, embedded systems in the 1960s to be used for the control of electro-mechanical telephone exchange was known as the "stored program control type system" (Stored Program Control).
 The real development of embedded computer is the microprocessor came after. November 1971, Intel Corporation succeeded in arithmetic and controller integrated circuit, introduced the first microprocessor Intel 4004, followed by the manufacturers launched a number of 8-bit, 16-bit microprocessor, including the Intel 8080/8085, 8086, Motorola's 6800,68000, and Zilog's Z80, Z8000 and so on. To those posed by the microprocessor as the core system, widely used in instrumentation, medical equipment, robotics, household appliances and other fields. Extensive use of microprocessors to form a broad embedded market, computer manufacturers in large quantities to provide users with plug-ins OEM products, and then by the users according to their need to choose a suitable CPU board, memory board, and all kinds of I / O plug-in boards, so as to constitute a dedicated embedded computer systems, and into their own system devices.
 For flexible compatibility considerations, there have been series, modular SBC. Popular single-board computer with Intel's iSBC series, Zilog's MCB and so on. Later, people do not have to choose the chip from the beginning to design a dedicated embedded computer, but as long as the choice of the function module, you can set up a dedicated computer system. Users and developers want to buy from different manufacturers the best OEM products purchased or made into the chassis to form a new system, so want the plug-compatible with each other, it led to the industrial control computer system bus was born. In 1976 Intel introduced Multibus, 1983 was extended to the bandwidth of 40MB / s of the Multibus Ⅱ. Designed in 1978 by the Prolog simple STD bus is widely used in small embedded systems.1980s can be said of the bus after another, pack and play times. With raising the level of micro-electronics technology, IC manufacturers began to embedded applications, microprocessors need, I / O interfaces, A / D, D / A converter, serial interface and RAM, ROM and other components all integrated into a VLSI, thus creating for I / O micro-controller design, what we called single-chip, embedded computer systems as the sudden emergence of a rookie. Subsequent development of DSP products are further enhanced the level of embedded computer systems technology, and rapidly penetrate into the consumer electronics, medical electronics, intelligent control, communications, electronics, instrumentation, transportation and other areas.
 1990s, in distributed control, flexible manufacturing, digital communications and information appliances such huge demand traction, to further accelerate the development of embedded systems. Signal processing algorithms for real-time DSP products toward high-speed, high precision, low-power development. Texas third-generation DSP chip TMS320C30, leading the 32-bit microcontrollers to high-speed intelligent development. In the application, PDA, handheld PC, set-top box technology is relatively mature, and more rapid development. Especially the Pocket PC 1997, Pocket PC in the U.S. market, but four of five brands, and the end of 1998, a wide range of handheld computers have mushroomed emerged. Additionally, Nokia introduced a smart phone, Siemens launched a set-top box, Wyse introduced the intelligent terminal, NS introduced WebPAD. Mounted on a small computer in the car, not only can control the car's various devices (eg, sound, etc.), you can also connect the GPS to automatically control vehicle. 21 century is the era of a network, the embedded computer system to be applied to various types of networks are bound to be an important direction for embedded system development.Feature1) small kernel. As embedded systems are generally used in small electronic devices, system resources are relatively limited, compared to a traditional operating system kernel is much smaller. Such as distributed system Enea's OSE kernel only 5K.2) specific and strong. Embedded systems highly personalized, one of the four kinds of software, embedded operating system scheduling mechanismSystem and hardware combination is very close, generally for the hardware system migration, even within the same brand, same series of products also need to increase or decrease in system hardware changes and continuous change. At the same time for different tasks, often need to carry out major changes to the system, procedures and systems to compile download combined this modification, and common software "upgrade" is a completely different concept.3) The system streamlined. Embedded systems generally do not have the system software and application software, the sharp distinction, does not require its functional design and implementation is too complex, so that on the one hand help control costs, but also conducive to system security.
 4) high real-time system software (OS) is the basic requirement of embedded software. Solid-state storage and the software required to improve the speed; software code quality and reliability requirements.5) Embedded software development in order to move toward standardization, it is necessary to use multi-tasking operating system. Embedded system applications without an operating system running directly on the chip; but for a reasonable schedule multiple tasks, the use of system resources, and expert system function library and function interface, the user must own matching RTOS (Real-Time Operating System) development platform, so as to ensure the execution of real-time, reliability, and reduce the development time to ensure software quality.6) The need to develop embedded systems development tools and environments. Because of its development does not have the ability to bootstrap, even if the design is completed the user usually can not be modified in which the program functions, must have a development tool and environment can be developed, these tools and the environment are generally based on a common computer software hardware devices and a variety of logic analyzers and mixed signal oscilloscope. Often when developing the concept of host and target host for the program development, implementation target machine as a last resort, need to develop alternate conjunction.CoreEmbedded system is the embedded microprocessor. Embedded microprocessors generally have the following four characteristics:
 1) has a strong support for real-time tasks ability to complete multi-task and have a shorter interrupt response time, so that the internal code within the core and real-time execution time is reduced to a minimum.2) has a highly functional storage area protection. This is due to the embedded system software architecture is modular, and between software modules in order to avoid errors in the cross effect, need to design powerful memory protection, but also conducive to the software diagnosis.3) scalable processor architecture to be the most rapidly develop applications to meet the highest performance embedded microprocessor.4) low-power embedded microprocessors must, especially for portable computing and wireless and mobile communication devices rely on battery-powered embedded systems, especially, if necessary, only mW or μW power level.