The so-called development, one-third by searching, seven by pasting ~
Let me talk about the embedded wailing. Embedded systems consist of hardware and software. The device is capable of independent operation. Its software includes only the operating environment software and operating system. Hardware aspects of the content includes a signal processor, a memory, a communication module, etc., compared to the general terms of computer processing system. The presence of large differences in the embedded system, it can not achieve a large capacity storage function, because the large-capacity medium is not matched, most of the storage media employed are E-PROM, EEPROM DENG, etc., software components to programming API interface as the core development platform.
Embedded system is application-centric, modern computer technology, special purpose computer system can be in accordance with user requirements (function, reliability, cost, size, power consumption, flexible environment, hardware and software modules of the crop.
Summarize points:
to apply centric: emphasize the target embedded systems to meet specific needs of users in terms of the vast majority of complete embedded system, turn the power user can enjoy its features directly, without secondary development with little or configuration operations.
dedicated : the embedded system applications often have higher requirements on reliability, real-time, which determines the service is the mainstream model of embedded systems in a dedicated system for a particular application, it does not emphasize the versatility and scalability of the system this specificity usually results in an embedded system is a tightly integrated hardware and software system eventually, because it can more effectively improve overall system reliability and reduce costs, and make it a better user experience
with modern computer as the core technology: basic support for embedded systems technology, generally including integrated circuit design High reliability software development technology, system architecture technology, sensor and detection technology, embedded real-time operating system and operating system technology, the limited system resources, system specifications and formal verification technology, communication technology, low-power technology, the specific application data analysis, signal processing and control optimization technology, the basic principles of which surround the computer, integrated into a specific dedicated equipment to form an embedded system.
Hardware and software can be cut: embedded system applications for the scene so much, and bring a great diversity of design requirements (functional performance, reliability, cost, power consumption), so the reality is difficult to have a set of solutions to meet all system requirements, according to different needs, flexible cutting hardware and software, set up to meet the requirements of the final system is an inevitable technology roadmap embedded technology development.
Hardware and embedded software systems must be based on the specific application task, the power consumption, cost, size, reliability, and processing capability to be selected as an index. The core embedded system is system software and application software, due to limited storage space, thus requiring the software code is compact, reliable, and there are strict real-time requirements.
From the composition point of view, the embedded system is a software and hardware in one, can work independently of the computer system; appearance, embedded systems such as a "programmable" electronic "devices"; from a functional point of view, it is the target system (host object) is controlled, so that the intelligent controller. From different angles of view of users and developers, as compared with a conventional computer, an embedded system has the following characteristics.
(1) specific and strong. As embedded systems are usually for a specific application, so the embedded system hardware and software, especially software, are designed for specific user groups, usually with some specificity characteristics.
(2) Small size. The general-purpose computer embedded computer systems by the board to complete a number of tasks integrated in the chip, which is conducive to miniaturization, easy to embedded systems embedded target system.
(3) real good. Embedded systems are widely used in the production process control, data acquisition, transmission and other communications applications, primarily used to control the host object, it is more or less real-time requirements of embedded systems. For example, weapons in embedded systems, industrial control devices in some of the control system of real-time requirements on high. Some systems are also not very high real-time requirements, for example, in recent years, relatively fast pace of development of handheld computers. But on the whole, it is a common requirement for real-time embedded systems, is an important indicator of designers and users should be a key consideration.
(4) can be a good crop of. Specific features of the embedded systems, the embedded system provider should offer a variety of hardware and software in an alternative use, strive to achieve higher performance on the same silicon area, in particular in order to application more competitive.
(5) high reliability. Since some embedded systems computing tasks undertaken involving key quality controlled products, personal safety equipment, even major affairs of state secrets, and the host object embedded systems in some work unattended occasions, such as at high risk industrial and environmental monitoring devices harsh field environments. Therefore, compared with the conventional systems, embedded systems extremely high reliability requirements.
(6) low power consumption. There are many embedded systems host objects are small applications, such as mobile phones, MP3, digital cameras, these devices can not be configured or larger capacity AC power supply, and therefore low-power embedded systems has been a goal .
(7) embedded system itself does not have the ability to self-development, development aid must be general-purpose computer platform. Embedded system design is completed, the average user is usually no way to program or hardware structure which may be modified, must have development tools and environments can take place.
(8) An embedded system usually uses the method "of hardware and software co-design" can be realized. The early design of embedded systems often used the "hardware first" principle, that is, in only a rough estimate of the software needs of the mission, the first hardware design and implementation, and software design on this hardware platform. If the traditional design method, once problems in testing, when the need for design changes throughout the design process will be re great impact on the cost and design cycle. Design of the system relies heavily on the designer's experience. Since the 1990s, with the development of chips and other electronic and related technologies, design and implementation of embedded systems hardware and software co-design methods appeared that the use of uniform methods and tools for software and hardware description, synthesis and verification. Under the guidance system objectives and requirements through a comprehensive analysis of existing system hardware and software functions and resources, collaborative design software and hardware architecture, system software and hardware in order to maximize our ability to avoid due to various independent software and hardware design architecture brought ills, obtain a high performance, low cost optimization of the design.
Wherein viewed from the outside, an embedded system is usually a fully functional, almost independent of other external devices to operate independently of the integrated hardware and software system. If subdivision of such a system, then it can be found generally may include several layers
embedded system hierarchy
core level embedded system is a central processing unit portion, which comprises a computing unit and a control module, in the cpu based on the memory module is further coupled, power modules, constitutes the reset module known as minimum system. Due to advances in technology, integrated circuit manufacturers will usually do a lot of peripherals into a single integrated circuit, which is more convenient in use, so often called a chip microcontroller. Expand upon the microcontroller on power detection sensor, actuator and supporting software modules and form a complete unit with a specific function, it is called an embedded system or embedded applications.
Hardware configuration
Although various specific functions of the embedded system, the appearance of the interface, not the same operation, or even vary, but the basic structure is similar to the hardware, and a general purpose computer system hardware, and has a high degree of similarity. Hardware of the embedded system looks no different from a general purpose computer system, also consist of a part of a processor, memory, external devices, I / O interfaces, graphics controller. But the characteristics of embedded system applications on embedded systems resulting in a greater difference in the composition and achieve formal general purpose computer system hardware and software. To meet the need for long-term preservation of data requirements in terms of speed, size and power consumption, operating system, application software, data and other special embedded systems typically do not use this type of disk has a large capacity storage medium and slow, and most of use EPROM, E2PROM or flash memory (Flash Memory). In embedded systems, A / D or D / A module is mainly used for monitoring and control, which is very little used in a general purpose computer. Depending on the application and size, some embedded systems to an external bus. With the rapid expansion of the field of embedded system applications, embedded systems become more and more personalized, according to their characteristics using the type of bus is also increasing. Further, in order to test the internal circuits embedded processor, a processor chip boundary scan test commonly used technique (JTAG).
Embedded systems hardware architecture
Software architecture
software architecture for embedded systems is the system-specific hardware for embedded system and user requirements and design, is an important part of embedded systems, embedded system is the key function. Similar embedded system software and a general purpose computer system software architecture is divided into a driver layer, operating system layer, middleware layer and application layer four, have their own characteristics.
Embedded system software architecture
driver layer
driver layer is a layer of dealing directly with the hardware, which provides hardware drivers or underlying core support for the operating system and applications. In embedded systems, sometimes called the driver board support package (BSP). BSP has the basic functions on the hardware environment of the embedded system initialization after power system, basic hardware includes a microprocessor, memory, interrupt controller, DMA, timers. Driver layer - generally three types of programs may be, i.e., board-level initialization procedure, a standard driver and application driver.
Operating system layer
embedded system operating system with the core functions of the operating system in general, responsible for allocating resources of all hardware and software for embedded systems, dispatching control, coordination of concurrent activities. It still has embedded features, are embedded operating system (Embedded Operating System, EOS). Mainstream embedded operating system Windows CE, Palm: OS, Linux , VxWorks.pSOS.QNX.LynxOS and so on. With an embedded operating system, the application is written faster, efficient and stable.
Middleware layer of
middleware software help and support for application software development, typically including databases, network protocols, graphics support and the corresponding development tools, such as: MySQL, TCP / IP, GU1 belong to this type of software.
Application layer
Embedded application software for specific applications, the software used to achieve the desired objectives of the user. Embedded application software and general application software is quite different, it requires not only in terms of accuracy, security and stability to meet the needs of practical applications, but also to optimize as much as possible, in order to reduce the consumption of system resources reduce hardware costs. Application software embedded systems is the most active force, each application has a specific application background. Despite a smaller scale, but highly specialized, so unlike the embedded application software and operating system support software as subject to foreign products, it is the dominant field of embedded software in China.
