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Nov 2 2019

Embedded Systems - Overview - Analysis of definitions

Introduction

With the rapid development of modern technology, embedded systems have penetrated into various fields of society, and embedded system products have been applied to every corner of people's daily life. Therefore, embedded system technology has become one of the hot research topics. But what are embedded systems? Everyone has different opinions, and there is no unified conclusion yet. For this reason, we need to explore to make embedded systems develop along a healthy path.


Catalog

Introduction

I What are Embedded Systems

1.1 Definition of Embedded System

1.2 Characteristics of Embedded System

II Compared with Dedicated Computer System

2.1 Develop Parallel Independence

2.2 Different Directions of Technological Development

2.3  Different Architecture

2.4 Different Function

III Diverse Technical Foundation

Conclusion


I What are Embedded Systems

1.1 Definition of Embedded System

For those who don't understand this knowledge, the term embedded system may seem more esoteric. In fact, the embedded system is very closely related to the life of ordinary people. Mobile phones and USB flash drives that you are familiar with is a typical embedded system; MP3, MP4, microwave oven or cable TV set-top box is also an embedded system; cars, ATMs, elevators, etc. are all embedded systems. All of these are only emotionally aware of embedded systems from the application side, but it is not the true meaning of embedded systems.

So what is the real meaning of embedded systems? The popular saying in China is: "Embedded systems are application-centric, computer-based, and software and hardware can be tailored, and are suitable for application-specific computer systems with strict requirements on function, reliability, cost, size, and power consumption." For this definition, I have two questions: First, the embedded system is "based on computer technology", which I think is not comprehensive. It ignores the important role of microelectronics and other technologies as the basis of embedded systems; Second, the definition of an embedded system as a "special computer system", I think is incorrect, it confuses the difference between embedded systems and computer systems. A professor has said: "Embedded systems are not dedicated computer systems, and embedded systems are an intelligent control system."

Why is the embedded system not a "dedicated computer system", not only "computer technology-based"? How to define an embedded system? Next we will analyze it from several aspects.

1.2 Characteristics of Embedded System

(1) Embedded systems characteristics are vary from its definition, and they are derived from the three basic elements of the definition. The features of different embedded systems will vary.

(2)  Features related to "embeddedness": Since it is embedded in the object system, it must meet the environmental requirements of the target system, such as the physical environment (small), electrical/atmosphere environment (reliable), and cost (cheap).

(3) Features related to "speciality": software and hardware tailoring; minimum software and hardware configuration to meet object requirements.

(4) Features related to "computer systems": Embedded systems must be computer systems that meet the control requirements of the target system. Corresponding to the above two features, such a computer must be equipped with an interface circuit that is compatible with the object system.


II Compared with Dedicated Computer System

 The term "dedicated computer system" should correspond to the term "universal computer system". From the literal point of view, whether it is "dedicated" or "universal", they are not separated from the scope of computer systems, it should be said that they belong to the computer system. Since it is computer system, their origin should be the computer. Their architecture, functional characteristics, knowledge systems, and technical requirements should have similarities. However, although the embedded system and the computer system are related, there is not much similarity in the above mentioned points, and how can it be indicated that it is a "special computer system".

2.1 Develop Parallel Independence

The embedded system has been independently developed for about 30 years. It and the computer system are two independent development systems. From their origin, both of them originated from semiconductor integrated circuits, which were born in the era of microcomputers.

Embedded systems originate from semiconductor integrated circuits, which are divided into transistors and integrated circuits. In the 1970s, integrated circuits produced microprocessors, which were intelligent cores with two functions. One is the arithmetic processing function, that is, the high-speed massive solution ability, which has promoted the rapid development of computer independence; Another is control function. The embedded system belongs to the control function, and the control function generates a microcontroller, commonly known as a single-chip microcomputer, which promotes the independent development of the embedded system.

In the 1970s, the control functions of microprocessors attracted the interest of control professionals. They embed the microcomputer into the object system, through electrical and mechanical reinforcement, and configure various peripheral interfaces, thus achieving intelligent control of the object system. Therefore, this microprocessor loses its original form and microcomputer functions, and the embedded computer system (referred to as the embedded system) is named after it. ince the embedded system needs to be embedded in the object device, the volume is required to be small, the function is reliable, and the cost is low, and the computer cannot assume the intelligent control task for the object system.

microprocessors

Microcontrollers are also single-chip microcontrollers in the traditional sense. It is characterized by small size, simple structure, easy development and economical price. It also can be said to be the predecessor of the current embedded system. The MCU integrates the main functions required by the object into a chip. Usually, a MCU chip contains an arithmetic processing unit, ARM, Flash memory, and some external interfaces. The external interface can output or input signals to control the corresponding device, and the user can program the written code into the microcontroller chip to control the external device. Single-chip microcomputers are often used in smart instruments, industrial measurement, and office automation. Such as digital meters, bus IC card system, printers, etc. have a microcontroller inside. From the history of the development of embedded systems, embedded systems originated from semiconductor integrated circuits. It does not originate from computers, so it is not a "special computer system", it is a dedicated intelligent control system. Therefore, the definition of an embedded system as a "special computer system" does not conform to history, and it is not advisable to confuse the essential difference between the two.

2.2 Different Directions of Technological Development

As the name suggests, embedded systems are embedded in the object system and organically combined with the object system to achieve intelligent control for the object system. It has completely different technical requirements and technological development directions from computers.

The embedded system requires the system to be intelligent and ultra-small in terms of form; from the function, it requires reliable function, low power consumption and economical benefits; from the scope of application, it should be market-oriented, user-oriented, object-oriented, and product-oriented; from technology, the requirement is to improve the intelligent control ability of the object, and the development direction is the embedded performance, control ability and control reliability closely related to the object.

While the computer system is visible and tangible, and does not need to be embedded in other devices from the form; functionally, it requires multiple processing functions; in terms of technology, it requires high-speed massive numerical calculation, infinite increase in bus speed, and continuous expansion of storage capacity.

In the early days, people reluctantly modified general-purpose computer systems to implement embedded applications in large devices. However, for many object systems (such as household appliances, instrumentation, industrial control units, etc.), it cannot be embedded in general-purpose computer systems, and the development direction of embedded systems is completely different from  the general-purpose computer systems. Therefore, it is necessary to independently develop a general-purpose computer system and an embedded computer system, which naturally form two major branches of modern computer technology development.

Therefore, embedded systems and computer systems have different technical requirements and technological development directions and should not be defined as "dedicated computer systems." If it is defined as "dedicated computer system", it means that the development of embedded systems should follow the development path of computer technology requirements, which hampers the healthy and open independent development of embedded systems.

2.3 Different Architecture

Embedded systems generally consist of embedded microprocessors, peripheral hardware devices, embedded operating systems, and user applications. They are used to implement control, monitoring, and management of other devices. The classic architecture of embedded systems has three levels of hardware and software, with four channel interfaces. Its channel interface is for embedding into the object system, and the interface system generates 4 interfaces. And its core is the embedded microprocessor, which is not a general purpose computer processor. In other words, the processors used by the two are quite different. After the embedded peripheral function is extended, the microcontroller is formed, and after its object interface technology is extended, the four interfaces generated form four interrupts of the entire on-chip structure of the SoC. Its software is divided into: instruction system, driver software, operating system 3 parts.

We see from the embedded system architecture:

Different processor. The computer is a general-purpose processor; the embedded system is a microprocessor for a specific application, which has the characteristics of low power consumption, small size, high integration, and the like, and the whole system design tends to be miniaturized.

The computer is a standard bus and peripherals, and the embedded bus and external interface are integrated in the processor. Computer software and hardware are relatively independent, while the embedded systems are tightly integrated with software and hardware, and the structure is more compact. The computer system focuses on multi-function processing settings, and the embedded system focuses on the control capability setting of the object.

Therefore, the embedded architecture is different from the computer’s. The embedded system architecture is controllable, not a processing architecture of a computer system. Different in structure, the nature is completely different, so the embedded system cannot be defined as a "special computer system."

2.4 Different Function

The embedded system has the characteristics of embedding and control,

and the hardware and software can be set according to the needs of the object. But computer systems are not same.

②Embedded systems have specific features, that is, software and hardware are designed specifically for a specific application system; computer systems are multi-functional processing.

③ Embedded systems have compact structure: software in an embedded system is generally not stored in a carrier such as a disk, but is solidified in the memory of a memory chip or a single-chip system. This design makes it extremely compact, resulting in small size, high efficiency, low cost, low power consumption. Computer structure requirements can be large or small, large to desktops, and small to laptops; Compared with the microprocessor of the embedded system, the requirement for the CPU is strict and generally expensive, which is not as low-cost and low-power as the embedded system. Embedded systems typically use flash memory as a storage medium to increase speed, reduce size, and reduce power consumption. While computers typically use large-capacity but slower storage media such as disks.

 The embedded system is intelligent, flexible and real-time: it is to react differently to different situations, and at the same time, the calculation results must be given and controlled in real time. But in this term the computer can't match.

 Embedded systems are highly reliable because of solidified software. For example, it is virus free. But computers are often attacked by viruses. Therefore, embedded systems are often used in major matters such as personal equipment security and state secrets.

 The computer industry is generally dominated by technology, such as Microsoft’s monopoly on computer operating systems. But in the field of embedded systems, this will not happen. Because it is a decentralized field full of competition, opportunity and innovation, no one's operating system and processor can monopolize the market.

All in all, embedded systems and computer systems have different functional characteristics, and the two cannot be confused.


III Diverse Technical Foundation

The embedded system knowledge system is extensive. It is closely related to microelectronics technology, computer science technology, electronic subject technology and object technology. In the embedded system, computer technology bears the task of building the application platform that includes the integrated development environment of embedded system, computer working method, programming language, programming method and so on. Although computer technology is one of the important foundations for building embedded system platforms, it is not the only one. And embedded systems also require additional technical support.

Microelectronics provides an integrated circuit foundation for embedded system applications; electronic technology provides circuit design techniques, which rapidly integrates integrated circuit design in microelectronics from circuit integration, functional integration, technology integration to knowledge integration, and provides hardware design technical support of embedded systems for computer technology. Object subject technology is the affiliation discipline of embedded system application, it covers almost all areas of technology, forming an infinitely large application area for embedded systems. And object subject should build an embedded application system in the field on the embedded system platform. The technical basis of the embedded application system is the basic theory and application environment and application requirements of the target discipline. At the same time, in the application, we must continuously put forward technical requirements for microelectronics, integrated circuit design, and embedded systems, so as to continuously improve the technical level of the embedded system platform. In the subject discipline, the vast majority of application engineers implement the most extensive applications on embedded software and hardware platforms. Figure 1 classifies embedded system independent knowledge technology systems:

 QQ截图20191102153807.png

Figure 1. Embedded Knowledge Technology System

As can be seen from Figure 2, the embedded system is a combination of advanced computer technology, semiconductor technology, microelectronics technology, electronic technology and various specific applications. It is a new integrated knowledge system that is technology-intensive, capital-intensive, highly fragmented and innovative. Similarly, it is based on the microelectronics, computer science, and electronic technology disciplines, and is based on the subject technology, and the technologies of each discipline are connected and support each other.  In other words, the embedded system embraces the strengths of each technology and draws on the essence of each profession to form its own unique knowledge and technology system. It can be seen from the above analysis that the embedded system is defined as "based on computer technology", which narrows the scope of embedded systems and denies the comprehensive application of various discipline technologies in embedded systems. Such definition is not comprehensive, with certain limitations, is not conducive to the establishment of a unique discipline system of embedded systems.


Conclusion

We discuss and analyze the definition of embedded systems from the aspects of embedded development origin, structural system, functional characteristics, and knowledge technology system to denied the statement that the embedded system is a "special computer system", and the embedded system is "based on computer technology", and found that the definition of the embedded system really needs to be improved. I support Professor He Limin's opinion: "Embedded systems are based on embedded microprocessors, based on microelectronics, computer technology, electronic technology, and object technology. And the hardware and software can be set according to the needs of the object and embedded in the object device, and is suitable for a dedicated intelligent control system with strict requirements on functions, reliability, cost, size, and power consumption of the application system.”In this way, the embedded system is no longer bound by the computer system. The embedded system can establish its own independent subject system. The embedded system teaching in the university is independent and formalized, and the embedded system can develop independently and healthily


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