Introduction to MCU

　　A single-chip microcomputer is a complete computer system integrated on a single chip . Although most of its functions are integrated on a small chip, it has most of the components required for a complete computer: CPU , memory , internal and external bus systems, and most of them also have external memory. At the same time, it integrates peripheral devices such as communication interfaces, timers , and real-time clocks. The most powerful single-chip microcomputer system can even integrate sound, images, networks, and complex input and output systems on a single chip.

　　The MCU is also called a microcontroller because it was first used in the field of industrial control. The MCU was developed from a dedicated processor with only a CPU in the chip. The earliest design concept was to integrate a large number of peripherals and the CPU into one chip to make the computer system smaller and easier to integrate into complex and demanding control devices. INTEL's Z80 was the first processor designed according to this idea. Since then, the development of MCUs and dedicated processors has gone their separate ways.

　　Early single-chip microcomputers were all 8-bit or 4-bit. The most successful one was INTEL's 8031, which was highly praised for its simplicity, reliability and good performance. After that, the MCS51 series of single-chip microcomputer systems were developed based on the 8031. Single-chip microcomputer systems based on this system are still widely used today. With the increasing requirements in the field of industrial control, 16-bit single-chip microcomputers began to appear, but they were not widely used because of their poor cost performance. After the 1990s, with the rapid development of consumer electronic products, single-chip microcomputer technology has been greatly improved. With the widespread application of the INTEL i960 series, especially the later ARM series, 32-bit single-chip microcomputers quickly replaced the high-end status of 16-bit single-chip microcomputers and entered the mainstream market. The performance of traditional 8-bit single-chip microcomputers has also been rapidly improved, and the processing power has increased hundreds of times compared with the 1980s. At present, the main frequency of high-end 32-bit single-chip microcomputers has exceeded 300MHz, and the performance is catching up with the dedicated processors in the mid-1990s. The factory price of ordinary models has fallen to US$1, and the highest-end models are only US$10. Contemporary single-chip microcomputer systems are no longer developed and used only in bare metal environments. A large number of dedicated embedded operating systems are widely used on a full range of single-chip microcomputers. High-end single-chip microcomputers that serve as core processors for handheld computers and mobile phones can even directly use dedicated Windows and Linux operating systems.

Microcontrollers are more suitable for embedded systems　　than dedicated processors , so they are used the most. In fact, microcontrollers are the most numerous computers in the world. Almost every electronic and mechanical product used in modern human life has a microcontroller integrated into it. Mobile phones, telephones, calculators, household appliances, electronic toys, PDAs, mice and other computer accessories are equipped with 1-2 microcontrollers. And there are also quite a few microcontrollers working in personal computers. Cars are generally equipped with more than 40 microcontrollers, and complex industrial control systems may even have hundreds of microcontrollers working at the same time! The number of microcontrollers not only far exceeds the combined number of PCs and other computers, but also exceeds the number of humans.

Introduction to MCU

    A single-chip microcomputer is also called a single-chip microcontroller. It is not a chip that completes a certain logical function, but a computer system integrated into one chip. In general, a chip becomes a computer. It is small in size, light in weight, and cheap in price, providing convenient conditions for learning, application, and development. At the same time, learning to use a single-chip microcomputer is the best choice to understand the principles and structure of computers.

    The microcontroller also uses modules similar to those in computers, such as CPU, memory, parallel bus, and storage devices that have the same functions as hard disks. The difference is that the performance of these components is much weaker than that of our home computers, but the price is also low, generally no more than 10 yuan... It is enough to use it to control some not very complicated work such as electrical appliances. We can see it in the fully automatic drum washing machine, exhaust hood, VCD and other home appliances we use now! ... It is mainly used as the core component of the control part.

    It is an online real-time control computer. Online means on-site control, which requires strong anti-interference ability and low cost. This is also the main difference from offline computers (such as home PCs).

    The microcontroller relies on programs and can be modified. Different functions can be realized through different programs, especially some special and unique functions, which other devices need to spend a lot of effort to achieve, and some are difficult to achieve even with great effort. If a not very complicated function is to be solved by pure hardware such as the 74 series developed in the 1950s in the United States, or the CD4000 series in the 1960s, the circuit must be a large PCB board! But if you use the series of microcontrollers successfully launched in the market in the 1970s in the United States, the results will be very different! Just because the microcontroller can achieve high intelligence, high efficiency, and high reliability through the program you write!

    Since MCU is cost-sensitive, the dominant software is still the lowest-level assembly language, which is the lowest-level language above binary machine code. Why use it if it is so low-level? Many high-level languages ​​have reached the level of visual programming, so why not use them? The reason is very simple, that is, MCU does not have a CPU like a home computer, nor does it have a massive storage device like a hard disk. Even if there is only one button in a small program written in a visual high-level language, it will reach a size of tens of KB! It is nothing for the hard disk of a home PC, but it is unacceptable for a MCU. The utilization rate of hardware resources of MCU must be very high, so although assembly is primitive, it is still widely used. In the same way, if the operating system and application software on a giant computer are taken to a home PC to run, the home PC will not be able to bear it.

    It can be said that the 20th century spanned three "electrical" eras, namely the electrical era, the electronic era, and the computer era that has now arrived. However, this type of computer usually refers to a personal computer, referred to as a PC. It consists of a host, a keyboard, a display, etc. There is another type of computer that most people are not very familiar with. This type of computer is a single-chip microcomputer (also known as a microcontroller) that gives intelligence to various machines. As the name suggests, the smallest system of this computer uses only one integrated circuit to perform simple calculations and controls. Because of its small size, it is usually hidden in the "belly" of the controlled machine. It plays a role like a human brain in the entire device. If it goes wrong, the entire device will be paralyzed. Now, this type of single-chip microcomputer has been used in a wide range of fields, such as intelligent instruments, real-time industrial control, communication equipment, navigation systems, household appliances, etc. Once various products use single-chip microcomputers, they can upgrade the products, and the adjective "intelligent" is often added before the product name, such as intelligent washing machines. Some products developed by technicians in some factories or other amateur electronic developers now have either too complicated circuits or too simple functions and are easily imitated. The reason may be that the product does not use a single-chip microcomputer or other programmable logic devices.

Application fields of single chip microcomputer

   At present, single-chip microcomputers have penetrated into every field of our lives. It is almost difficult to find a field without single-chip microcomputers. Missile navigation devices, control of various instruments on aircraft, computer network communication and data transmission, real-time control and data processing of industrial automation processes, widely used smart IC cards, safety systems of civilian luxury cars, control of video recorders, cameras, fully automatic washing machines, as well as program-controlled toys, electronic pets, etc., all of these are inseparable from single-chip microcomputers. Not to mention robots, intelligent instruments, and medical equipment in the field of automatic control. Therefore, the study, development, and application of single-chip microcomputers will create a group of scientists and engineers in computer application and intelligent control.

    Single chip microcomputers are widely used in the fields of instrumentation, household appliances, medical equipment, aerospace, intelligent management and process control of special equipment, etc., which can be roughly divided into the following categories:

1. Application in intelligent instruments

　　Single-chip microcomputers have the advantages of small size, low power consumption, strong control function, flexible expansion, miniaturization and easy use. They are widely used in instruments and meters. Combined with different types of sensors , they can measure physical quantities such as voltage, power, frequency, humidity, temperature, flow, speed, thickness, angle, length, hardness, elements, pressure, etc. The use of single-chip microcomputer control makes instruments and meters digital, intelligent, and miniaturized, and their functions are more powerful than those using electronic or digital circuits. For example, precision measuring equipment (power meters, oscilloscopes , various analyzers).

2. Application in industrial control

　　Single chip microcomputers can be used to form various control systems and data acquisition systems, such as intelligent management of factory assembly lines, intelligent elevator control, various alarm systems, and networking with computers to form a secondary control system.

3. Application in household appliances

　　It can be said that most of the current household appliances are controlled by single-chip microcomputers, ranging from rice cookers, washing machines, refrigerators, air conditioners, color TVs, other audio and video equipment, to electronic weighing equipment, which are diverse and ubiquitous.

4. Application in computer network and communication fields

　　Modern single-chip microcomputers generally have communication interfaces, which can easily communicate data with computers, providing excellent material conditions for their application in computer networks and communication equipment. Currently, most communication equipment has realized single-chip microcomputer intelligent control, from mobile phones, telephones, small programmable switches , building automatic communication call systems, train wireless communications, to mobile phones that can be seen everywhere in daily work, cluster mobile communications, radio walkie-talkies, etc.

5. Application of single chip microcomputer in medical equipment field

　　Microcontrollers are also widely used in medical equipment, such as medical ventilators, various analyzers, monitors, ultrasonic diagnostic equipment, bed call systems, etc.

In addition, single-chip microcomputers have a wide range of uses in industry and commerce, finance, scientific research, education, national defense, aerospace and other fields.

Microcontroller learning:

　　At present, many people do not approve of assembly language. It can be said that mastering the C language microcontroller programming is very important, which can greatly improve the efficiency of development. However, beginners do not need to understand the assembly language of the microcontroller, but they must understand the specific performance and characteristics of the microcontroller, otherwise it will be fatal in the field of microcontrollers. If you do not consider the hardware resources of the microcontroller and program randomly in C in KEIL, the result can only be that there is a problem that cannot be solved! It can be said with certainty that the best C language microcontroller engineers are programmers who come out of assembly because although the C language of the microcontroller is a high-level language, it is different from VC++ on desktop personal computers. The hardware resources of the microcontroller are not very powerful, which is different from us using VC, VB and other high-level languages ​​to write programs on desktop PCs. After all, the hardware of desktop computers is very powerful, so we can ignore the problem of hardware resources.