What is an embedded system? Embedded systems and microcontroller have any connection?

I. History of the technological development of modern computers

1. Embedded applications that began in the era of microcomputers

Electronic digital computers were born in 1946, and in the course of its long history since then, the computer has always been fed in the special machine room, the realization of the numerical calculations of the large and expensive equipment. Until the 1970s, the emergence of microprocessors, computers have seen a historic change. Microprocessor as the core of the microcomputer with its small, inexpensive, high reliability characteristics, quickly out of the engine room; based on high-speed numerical solving capacity of the microcomputer, the level of intelligence shown caused by the control of professionals interested in the requirements of the microcomputer embedded in a system of objects, to achieve the intelligent control of the object system. For example, the microcomputer by electrical reinforcement, mechanical reinforcement, and configure a variety of peripheral interface circuits, installed in large ships constitute an autopilot or turbine status monitoring system. In this way, the computer will lose its original form and general-purpose computer functions. In order to distinguish the original general-purpose computer system, embedded in the object system, the object system to achieve intelligent control of the computer, called the embedded computer system. Therefore, the embedded system was born in the era of microcomputer, embedded system of embedded nature is a computer embedded in an object system, these are the basic starting point for understanding the embedded system.

2. Two major branches of modern computer technology

As the embedded computer system to be embedded in the object system, the realization of the intelligent control of the object, therefore, it has a completely different technical requirements and technical development direction with the general-purpose computer system. The technical requirements of a general-purpose computer system are high-speed, massive numerical calculations; the direction of technological development is the unlimited improvement of bus speed and the unlimited expansion of storage capacity. The technical requirements of the embedded computer system is the object of intelligent control capability; the direction of technological development is closely related to the object system embedded performance, control capability and control reliability.

In the early days, people reluctantly modified general-purpose computer systems to realize embedded applications in large-scale devices. However, for many object systems (such as household appliances, instrumentation, industrial control units ......), can not be embedded in a general-purpose computer system, and moreover, embedded systems and general-purpose computer systems, the direction of technological development is completely different, therefore, it is necessary to develop independently of the general-purpose computer system and the embedded computer system, which has formed a modern

If you want to know more about the development of computer technology, then you should consider the following

If the emergence of the microcomputer, so that the computer into the modern computer development stage, then the birth of the embedded computer system, it marks the computer into the general-purpose computer systems and embedded computer systems two branches of the parallel development of the era, which led to the end of the twentieth century, the computer's high-speed development period.

3. Milestones in the development of the two branches

The development of general-purpose computer systems and embedded computer systems specialized division of labor, leading to the end of the 20th century, the beginning of the 21st century, the rapid development of computer technology. The computer professional field to concentrate on the development of general-purpose computer systems, software and hardware technology, do not have to take into account the requirements of embedded applications, general-purpose microprocessors quickly from 286, 386, 486 to the Pentium series; the operating system is a rapid expansion of the computer based on the high-speed massive data file processing capabilities, so that the general-purpose computer systems to enter into the stage of excellence.

Embedded computer systems have embarked on a completely different path, this independent development of the road is a single chip road. It mobilized the original traditional electronic systems in the field of manufacturers and professionals, took over the origin of the computer field of embedded systems, take up the development and popularization of embedded systems of the historical task, and rapidly develop the traditional electronic systems to the intelligent modern electronic systems era.

Therefore, the milestone significance of the two major branches of the development of modern computer technology lies in the fact that it not only forms a specialized division of labor for the development of computers, but also extends the task of developing computer technology to the field of traditional electronic systems, so that computers become a powerful tool to enter the era of comprehensive intelligence of human society.

Two, the definition and characteristics of embedded systems

If we understand the origin and development of embedded (computer) systems, the embedded system will not produce too many misunderstandings, and can be historically, essentially, universally applicable definition of embedded systems.

1. Definition of Embedded System

In accordance with the historical, essential and universal requirements, embedded system should be defined as: "a specialized computer system embedded in the object system". "Embeddedness", "specialization" and "computer system" are the three basic elements of an embedded system. The object system is the host system in which the embedded system is embedded.

2. Characteristics of Embedded Systems

The characteristics of embedded systems are different from the definition, which is derived from the three basic elements in the definition. The characteristics of an embedded system will vary from one embedded system to another. Characteristics related to "embeddedness": Because it is embedded in the object system, it must meet the environmental requirements of the object system, such as the physical environment (small size), the electrical/atmospheric environment (reliable), the cost (inexpensive) and other requirements. Characteristics related to "specialization": Tailorability of software and hardware; minimum software and hardware configurations to meet the requirements of the object. Characteristics related to the "computer system": embedded systems must be able to meet the object system control requirements of the computer system. With the last two features echo, such a computer must be configured with the object system compatible interface circuitry.

Also, in understanding the definition of an embedded system, do not confuse it with an embedded device. Embedded devices are products and devices that have embedded systems inside, for example, home appliances, instrumentation, industrial control units, robots, cell phones, PDAs, etc. that contain microcontrollers inside.

3. Types and development of embedded systems

According to the above definition of embedded systems, as long as the computer system that meets the three elements of the definition, can be called an embedded system. Embedded systems can be categorized by form into device level (industrial controllers), board level (single boards, modules), and chip level (MCUs, SoCs).

Some people think of embedded processors as embedded systems, but since an embedded system is an embedded computer system, such a computer system can be called an embedded system only if the embedded processor constitutes a computer system and is used as an embedded application.

Embedded systems are closely related to the object system, and its main direction of technological development is to meet the requirements of embedded applications, and constantly expand the peripheral circuits required by the object system (e.g., ADC, DAC, PWM, calendar clocks, power supply monitoring, and program operation monitoring circuits), to form an application system that meets the requirements of the object system. Therefore, the embedded system, as a specialized computer system, has to keep developing into a computer application system. Therefore, it is possible to extend the definition of a dedicated computer system into a computer application system that meets the requirements of the object system.

Three, the independent development of embedded systems road

1. Microcontroller created the independent development of embedded systems road

Although the embedded system originated in the era of microcomputer, however, the volume of microcomputer, price, reliability can not meet the majority of the object of the system's embedded application requirements, so the embedded system must take the road of independent development. This road is the chip-based road. The computer will be done on a chip, thus creating the embedded system independent development of the microcontroller era.

When exploring the development path of microcontroller, there have been two modes, namely, "∑ mode" and "innovation mode". "∑ mode" is essentially a general-purpose computer direct chip mode, it will be a general-purpose computer system in the basic unit for cutting, integrated in a chip, constituting a single microcomputer; "innovation mode" is completely embedded application requirements for the design of a new, meet the requirements of embedded applications MCS-48 and MCS-51 are the embedded systems (single chip microcomputer) developed according to the innovation mode, and MCS-51 is the embedded system based on the exploration of MCS-48, which is a comprehensive and perfected embedded system. History proves that "innovation mode" is the right path for the independent development of embedded systems, and the architecture of MCS-51 has become the typical structure of monolithic embedded systems.

2. History of microcontroller technology development

Microcontrollers were born at the end of the 1970s, and have gone through three major phases: SCM, MCU, and SoC.

1. SCM that is, Single Chip Microcomputer (Single Chip Microcomputer) stage, mainly to seek the best monolithic form of the best embedded systems architecture. The success of the "innovation model" has laid the foundation for the development of SCM and general-purpose computers completely different path. In the creation of embedded systems in the independent development of the road, Intel Corporation can not be credited.

2. MCU that is, microcontroller (Micro Controller Unit) stage, the main direction of technological development is: constantly expanding to meet the embedded applications, the object of the system requirements of a variety of peripheral circuits and interface circuits, highlighting the object of its intelligent control capabilities. It involves the fields related to the object system, therefore, the development of MCU's heavy responsibility inevitably falls on the electrical and electronic technology manufacturers. From this perspective, Intel's gradual fade out of MCU development also has its objective factors. In the development of MCU, the most famous manufacturers when the Philips Corporation.

Philips company with its great advantage in embedded applications, MCS-51 from a single microcomputer to microcontroller rapid development. Therefore, when we review the development path of embedded systems, do not forget the historical merits of Intel and Philips.

3. Microcontroller is the road to independent development of embedded systems, to the MCU stage of the development of important factors, is to seek the application of the system on a chip to maximize the solution; therefore, the development of dedicated microcontroller naturally formed the SoC trend. With the development of microelectronics technology, IC design, EDA tools, SoC-based microcontroller application system design will have greater development. Therefore, the understanding of microcontroller can be extended from a single microcomputer, single microcontroller to a single application system.

Four, the two application modes of embedded systems

Embedded systems embedded application characteristics, determines its multidisciplinary cross characteristics. As a computer embedded, the requirements of the computer field personnel to intervene in its architecture, software technology, engineering applications. However, understanding the control requirements of the object system and realizing the system control mode must have the expertise of the object field. Therefore, from the historical process of the development of embedded systems, as well as the diversity of embedded applications, it is possible to understand the objective formation of two application modes.

1. Objective existence of the two application modes

Embedded computer systems originated in the era of microcomputer, but soon entered the era of independent development of microcontroller. In the era of microcontroller, embedded systems in the form of devices quickly into the field of traditional electronic technology, electronic technology application engineers as the main body to achieve the intelligence of traditional electronic systems, and computer professional team did not really enter the field of microcontroller applications. Therefore, electronic technology application engineers are engaged in the application development of microcontroller with their own customary electronic technology application mode. The most important features of this application mode are: the underlying software and hardware and arbitrariness; the close correlation of object system expertise; and the lack of computer engineering design methods.

Although in the era of microcontroller, computer professionals faded out of the embedded systems field, but with the arrival of the post-PC era, the network, communication technology can be developed; at the same time, the embedded system software and hardware technology has been greatly improved, for computer professionals to intervene in the application of embedded systems to open up a wide world. The intervention of computer professionals, the formation of the computer application model with obvious computer engineering applications, that is, based on the embedded system software, hardware platform, network, communication-based non-embedded bottom application.

2. Co-existence and complementarity of the two application modes

As the embedded system is the largest, broadest, the most bottom of the application is the intelligent transformation of the traditional field of electronic technology, therefore, the object of professional knowledge of the electronic technology team is mainly, with the least amount of embedded system software, hardware overhead, 8-bit machine-based, with a strong color of the design of electronic systems electronic system application mode will be Long-term existence.

In addition, computer professionals will increasingly intervene in the embedded system applications, but confined to the object of the professional knowledge of the disconnect, its application areas will be concentrated in the network, communications, multimedia, business electronics, etc., it is not possible to replace the original electronic engineers in the control, instrumentation, mechanical and electronic aspects of the embedded applications. Therefore, the objective existence of the two application modes will coexist for a long time, complementing each other in different fields. Electronic system design mode should be from the computer application design mode, learning computer engineering methods and embedded system software technology; computer application design mode should be from the electronic system design mode, to understand the embedded system application of circuit system characteristics, the basic peripheral circuit design methods and the basic requirements of the object system.

3. Embedded system applications of the high and low ends

As the embedded system has had a long period of independent development of the road of the microcontroller, mostly based on the 8-bit microcontroller, the realization of the lowest level of embedded system applications, with the obvious characteristics of the electronic system design mode. Most of the developers engaged in microcontroller applications, are object systems in the field of electronic systems engineers, coupled with the emergence of microcontrollers, immediately out of the field of computer expertise to "intelligent" device identity into the field of electronic systems, did not bring into the "embedded system" concept. The concept of "embedded system" was not brought in. Therefore, many people engaged in microcontroller applications, do not understand the relationship between microcontroller and embedded systems, in the field of "embedded systems", often understood as a specialized field of computer, based on the 32-bit embedded processor, engaged in networking, communications, multimedia applications. In this way, "microcontroller" and "embedded systems" form two independent terms common in embedded systems. However, since "microcontroller" is a typical embedded system developed independently, it should be unified into "embedded system" from the perspective of discipline construction. Considering the characteristics of the original microcontroller's electronic system bottom application, the embedded system application can be divided into high-end and low-end, the original microcontroller application is understood as the low-end application of the embedded system, which means its bottom nature and the tight coupling with the object system.

Excerpted from Microcontroller and Embedded System Applications