I. What is an embedded system?
While computer, internet, and communication technologies have developed rapidly, embedded system development technology has also made rapid progress. This is reflected not only in the dramatic expansion of the application scope of embedded technology, but also in the enhanced performance, increasing maturity, and product upgrades of embedded processors and real-time operating systems.
Currently, many people in the field of embedded systems applications lack a clear understanding of what an embedded system is. Some, when explaining what an embedded system is, do not start with the definition but instead list some characteristics, often resulting in unclear and confusing explanations. Therefore, it is necessary to clarify this point.
An embedded system is an application-centric, computer technology-based embedded computer system with customizable software and hardware. It is suitable for application systems with strict requirements on functionality, reliability, cost, size, and power consumption. It generally consists of four parts: an embedded microprocessor, peripheral hardware devices, an embedded operating system, and user applications, used to implement functions such as device control, monitoring, and management.
Because embedded computer systems are integrated into application systems to achieve intelligent control, they have completely different technical requirements and development directions compared to general-purpose computer systems. General-purpose computer systems require high-speed, massive-scale numerical computation; their development direction is the unlimited increase in bus speed and the unlimited expansion of storage capacity. Embedded computer systems, on the other hand, require intelligent control capabilities for the application; their development direction is the embedding performance, control capabilities, and control reliability closely related to the application system. Therefore, the milestone significance of these two branches of modern computer technology development lies in the fact that they not only formed a specialized division of labor in computer development but also extended the task of developing computer technology to the traditional field of electronic systems, making computers a powerful tool for entering a fully intelligent era for human society.
Today, embedded systems are ubiquitous, found in everything from automobiles, home microwave ovens, PDAs, and televisions to industrial control production sites, packaging, printing, communications, instruments, meters, ships, aviation, aerospace, military equipment, and consumer products.
II. Classification and Characteristics of Embedded Systems
1. Classification of Embedded Systems
Some people mistakenly consider a single embedded microprocessor as an embedded system. An embedded system is essentially an embedded computer system; therefore, only when an embedded microprocessor is incorporated into a computer system and used in embedded applications can such a computer system be called an embedded system.
Embedded systems can be classified in different ways depending on the classification criteria. For example, based on their form, embedded systems can generally be divided into three levels: chip-level (MCU, SoC), board-level (microcontroller, module), and device-level (industrial control computer). Based on their complexity, embedded systems can also be divided into the following four categories:
(1) Embedded systems mainly composed of microprocessors are often used in small devices (such as temperature sensors, smoke and gas detectors, and circuit breakers); (2) Microprocessor devices without timing functions can be found in process control, signal amplifiers, position sensors, and valve actuators; (3) Components with timing functions are commonly found in switching devices, controllers, telephone exchanges, packaging machines, data acquisition systems, medical monitoring systems, diagnostic and real-time control systems, etc.; (4) Computer systems used in manufacturing or process control, which are embedded computer systems composed of industrial control computers, are the most complex of these four types. They are also frequently used in modern printing equipment.
2. Characteristics of Embedded Systems
(1) Embedded systems are products that combine advanced computer technology, semiconductor technology, and electronic technology with specific applications in various industries. This determines that it is inevitably a technology-intensive, capital-intensive, highly decentralized, and constantly innovative knowledge integration system. Embedded CPUs can integrate many tasks that are performed by boards in general-purpose CPUs into the chip itself, which is conducive to the miniaturization of embedded system design, greatly enhances mobility, and makes the coupling with networks increasingly tighter.
(2) The hardware and software of embedded systems must be designed efficiently, tailored to specific needs, and redundant components should be removed in order to achieve higher performance on the same silicon wafer area. This will make the selection of microprocessors more competitive in specific applications.
(3) Embedded systems and specific applications are organically combined, and their upgrades and replacements are carried out in sync with specific products. Therefore, once embedded system products enter the market, they have a long life cycle.
(4) In order to improve execution speed and system reliability, the software in embedded systems is generally embedded in the memory chip or the microcontroller itself, rather than stored on the disk or other media.
(5) Embedded systems do not have self-bootstrapping capabilities. Even after the design is completed, users usually cannot modify the programs or functions. Moreover, a set of development tools and environment are required for development.
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