Service Hotline
News
News
MCU’s strongest popular science summary
2022-03-16
523
MCU is Microcontroller Unit The abbreviation of microcontroller in Chinese, commonly known as single-chip microcomputer, is to appropriately reduce the frequency and specifications of the CPU, and integrate peripheral interfaces such as memory, counter, USB, A/D conversion, UART, PLC, DMA, and even LCD driver circuits on a single chip to form a chip-level computer. It can perform different combinations of control for different applications, such as mobile phones, PC peripherals, remote controls, automotive electronics, industrial stepper motors, and robot arm control. MCU can be seen in the figure.
one
A brief history of the development of microcontrollers
The history of microcontrollers is not long, but it has developed very rapidly. Its production and development are generally synchronized with the production and development of microprocessors (CPUs). Since Intel Corporation of the United States first launched a 4-bit microprocessor in 1971, its development so far can be roughly divided into five stages. The following is an introduction to the development of microcontrollers from Intel Corporation.
1971~1976
The initial stage of the development of microcontrollers. In November 1971, Intel first designed the Intel 4004, a 4-bit microprocessor with an integration of 2,000 transistors/chip, equipped with RAM, ROM and shift register, forming the first MCS-4 microprocessor. Then it launched the 8-bit microprocessor Intel 8008, and other 8-bit microprocessors launched by other companies.
1976~1980
Low performance microcontroller stage. Represented by the MCS-48 series launched by Intel in 1976, it uses a monolithic structure that integrates an 8-bit CPU, 8-bit parallel I/O interface, 8-bit timer/counter, RAM and ROM on a semiconductor chip. Although its addressing range is limited (no more than 4 KB), there is no serial I/O, RAM and ROM capacity is small, and the interrupt system is relatively simple, but its functions can meet the needs of general industrial control and intelligent instruments and meters.
1980~1983
High-performance microcontroller stage. The high-performance 8-bit microcontrollers launched at this stage generally have serial ports, multi-level interrupt processing systems, and multiple 16-bit timers/counters. The capacity of the on-chip RAM and ROM is increased, and the addressing range can reach 64 KB. Some chips also have an A/D conversion interface.
1983~late 1980s
16-bit microcontroller stage. In 1983, Intel launched the high-performance 16-bit microcontroller MCS-96 series. Due to its adoption of the latest manufacturing technology, the chip integration level is as high as 120,000 transistors/chip.
1990s
Microcontrollers are developing to a higher level in all aspects of integration, functionality, speed, reliability, and application fields.
two
Classification and application of single chip microcomputer
MCUs can be divided into two types according to their memory types: those without on-chip ROM and those with on-chip ROM. For chips without on-chip ROM, an external EPROM must be connected before they can be used (typically 8031); chips with on-chip ROM are divided into on-chip EPROM type (typical chip is 87C51), MASK on-chip mask ROM type (typical chip is 8051), on-chip Flash type (typical chip is 89C51) and other types.
According to the purpose, it can be divided into general-purpose and special-purpose types; according to the width of the data bus and the length of data bytes that can be processed at one time, it can be divided into 8, 16, and 32-bit MCUs.
At present, the most extensive domestic MCU application market is in the consumer electronics field, followed by the industrial field and the automotive electronics market. Consumer electronics includes household appliances, televisions, game consoles, audio and video systems, etc. Industrial fields include smart homes, automation, medical applications, and new energy generation and distribution. The automotive field includes automotive powertrain and safety control systems.
three
Basic functions of microcontroller
For most MCUs, the following functions are the most common and basic. For different MCUs, the way they are described may be different, but they are essentially the same:
1. TImer (timer): Although there are many types of TImer, they can be summarized into two categories: One type is TImer with fixed time intervals, that is, the timing time is set by the system and cannot be controlled by the user program. The system only provides several fixed time intervals for the user program to choose, such as 32Hz, 16Hz, 8Hz, etc. This type of TImer is more common in 4-bit MCUs, so it can be used to implement clock, timing and other related functions.
The other type is Programmable Timer. As the name suggests, the timing time of this type of Timer can be controlled by the user's program. The control methods include: selection of clock source, selection of frequency division (Prescale) and setting of preset number. Some MCUs have all three at the same time, while others may have one or two of them. This type of Timer application is very flexible, and its actual use is also ever-changing. One of the most common applications is to use it to implement PWM output.
Since the clock source can be freely selected, this type of Timer is generally combined with the Event Counter.
2. IO ports: Any MCU has a certain number of IO ports. Without IO ports, the MCU loses the channel to communicate with the outside world. According to the configurability of the IO port, it can be divided into the following types:
Pure input or pure output port: This type of IO port is determined by the MCU hardware design. It can only be input or output, and software cannot be used for real-time settings.
Directly read and write IO ports: For example, the IO port of MCS-51 belongs to this type of IO port. When the read IO port instruction is executed, it is an input port; when the write IO port instruction is executed, it is automatically an output port.
Programming to set the input and output direction: The input or output of this type of IO port is set by the program according to actual needs. The application is relatively flexible and can realize some bus-level applications, such as I2C bus, various LCD, LED Driver control buses, etc.
For the use of IO ports, an important point that must be kept in mind is: for the input port, there must be a clear level signal to ensure that it cannot float (this can be achieved by adding a pull-up or pull-down resistor); for the output port, the output status level must consider its external connection conditions, and it should be ensured that there is no current pulling or sinking in the standby or static state.
3. External interrupt: External interrupt is also a basic function of most MCUs. It is generally used for real-time triggering of signals, data sampling and status detection. The interrupt methods include rising edge trigger, falling edge trigger and level trigger. External interrupts are generally implemented through input ports. If it is an IO port, its interrupt function will be turned on only when it is set to input; if it is an output port, the external interrupt function will be automatically turned off (there are some exceptions in ATMEL's ATiny series, which can also trigger the interrupt function when it is an output port). The applications of external interrupts are as follows:
Detection of external trigger signals: One is based on real-time requirements, such as control of thyristors, detection of sudden signals, etc., while the other is the need to save power.
Measurement of signal frequency: In order to ensure that the signal is not missed, external interrupt is the ideal choice.
Decoding of data: In the field of remote control applications, in order to reduce the cost of design, it is often necessary to use software to decode various encoded data, such as the decoding of Manchester and PWM encoding.
Key detection and system wake-up: For MCUs that enter the sleep state, they generally need to be awakened through external interrupts. The most basic form is a key press, which produces level changes through the action of the key.
4. Communication interface: The communication interface provided by MCU generally includes SPI interface, UART, I2C interface, etc., which are described as follows:
SPI interface: This type of interface is the most basic communication method provided by most MCUs. Its data transmission is controlled by a synchronous clock. The signals include: SDI (serial data input), SDO (serial data output), SCLK (serial clock) and Ready signal; in some cases, there may be no Ready signal; this type of interface can work in master mode or Slave mode. In popular terms, it depends on who provides the clock signal. The party providing the clock is the master, and the opposite party is the Slaver.
UART (Universal Asynchronous Receive Transmit): It is the most basic asynchronous transmission interface. It has only two signal lines, Rx and Tx. The basic data format is: Start Bit + Data Bit (7-bits/8-bits) + Parity Bit (Even, Odd or None) + Stop Bit (1~2Bit). The time occupied by one bit of data is called Baud Rate.
For most MCUs, the length of data bits, data check mode (odd check, even check or no check), stop bit length and Baud Rate can be flexibly set through program programming. The most commonly used method of this type of interface is to communicate with the serial port of a PC.
I2C interface: I2C is a data transmission protocol developed by Philips. It is also implemented using 2 signals: SDAT (serial data input and output) and SCLK (serial clock). Its biggest benefit is that multiple devices can be attached to this bus and identified and accessed through addresses; one of the biggest benefits of the I2C bus is that it is very convenient to use software to implement it through the IO port. Its transmission data rate is completely controlled by SCLK, which can be fast or slow, unlike the UART interface, which has strict rate requirements.
5. Watchdog (watchdog timer): Watchdog is also a basic configuration of most MCUs (some 4-bit MCUs may not have this function). The Watchdog of most MCUs can only allow the program to reset it but not turn it off (some are set when the program is burned in, such as Microchip PIC series MCU), and some MCUs use a specific method to decide whether to turn it on, such as Samsung's KS57 series. As long as the program accesses the Watchdog register, it is automatically turned on and cannot be turned off again. Generally speaking, the reset time of watchdog can be set programmably. The most basic application of Watchdog is to provide a self-recovery capability for MCUs that crash due to unexpected failures.
Four
Global mainstream microcontroller manufacturer
Tips for learning microcontrollers
Microcontroller programming
It is necessary to prevent the same variable or data from being accessed or set in the interrupt and main program bodies at the same time. An effective prevention method is to arrange the processing of such data in a module, and determine whether to perform related operations on the data by judging the trigger flag; in other program bodies (mainly interrupts), only set trigger flags where the data needs to be processed. --This ensures that data execution is predictable and unique.
In the development of microcontroller applications, problems such as code usage efficiency, anti-interference performance and reliability of microcontrollers are still troubled. Now we summarize several basic skills that should be mastered in the development of microcontroller.
eight
Microcontroller development skills
1 How to reduce bugs in programs
Regarding how to reduce program bugs, you should first consider the following out-of-range management parameters that should be considered during system operation.
- Physical parameters: These parameters are mainly input parameters of the system, which include excitation parameters, operating parameters during acquisition processing and result parameters at the end of processing.
- Resource parameters: These parameters are mainly the resources of circuits, devices, and functional units in the system, such as memory capacity, storage unit length, and stacking depth.
- Application parameters: These application parameters often appear as application conditions of some microcontrollers and functional units. Process parameters: refers to the parameters that change in an orderly manner during system operation.
2 How to improve the efficiency of C language programming code
Using C language for microcontroller programming is an inevitable trend in the development and application of microcontrollers. If you want to achieve maximum efficiency when programming in C, it is best to be familiar with the C compiler you are using. First test the number of lines of assembly language statements corresponding to each C language compilation, so that you can clearly know the efficiency. When programming in the future, use the statement with the highest compilation efficiency. Each C compiler will have certain differences, so the compilation efficiency will also be different. The code length and execution time of an excellent C compiler for embedded systems are only 5-20% longer than the same function written in assembly language.
For complex projects with tight development time, C language can be used, but the prerequisite is that you are very familiar with the C language and C compiler of the MCU system. Pay special attention to the data types and algorithms supported by the C compilation system. Although C language is the most common high-level language, different MCU manufacturers have different C language compilation systems, especially in the operation of some special function modules. Therefore, if you do not understand these features, there will be many problems during debugging, which will lead to lower execution efficiency than assembly language.
The most effective way to prevent interference is to remove the interference source and block the interference path, but it is often difficult to do so, so we can only see whether the anti-interference ability of the microcontroller is strong enough. While improving the anti-interference ability of hardware systems, software anti-interference is receiving more and more attention because of its flexible design, saving of hardware resources, and good reliability.
The most common phenomenon of microcontroller interference is reset. As for the program running away, software traps and watchdogs can actually be used to bring the program back to the reset state. Therefore, the most important thing for microcontroller software to resist interference is to handle the reset state.
Generally, microcontrollers will have some flag registers that can be used to determine the cause of reset; in addition, you can also bury some flags in RAM yourself. Each time the program is reset, different reset causes can be determined by judging these flags; you can also jump directly to the corresponding program based on different flags. This allows the program to run continuously, and the user will not notice that the program has been reset when using it.
4 How to test the reliability of the microcontroller system
When a microcontroller system design is completed, there will be different test items and methods for different microcontroller system products, but some must be tested:
- Test the completeness of the microcontroller software function
- Power on and power off test
- Aging test
- Tests such as ESD and EFT
Sometimes, we can also simulate the damage that may occur during human use. For example, deliberately rub the contact port of the microcontroller system with the human body or clothing fabric to test the anti-static ability. Use a high-power electric drill to work close to the microcontroller system to test the ability to resist electromagnetic interference.
In addition, during the development and application process, we must master skills and improve efficiency so that it can be used for a wider range of purposes.
Nine
Chip operation summary
The operations on the chip are mainly operations on the registers in the chip. The registers in the chip have their own unique addresses mapped on the memory, which is the operation on the corresponding address. When looking at the chip, first look at the timing diagram, then understand the corresponding registers, understand how they operate, define the required ports (which can be identified by the program), and write write operation procedures and read operation procedures.
In order to output Chinese characters on a monitor or printer, the Chinese characters are designed into a dot matrix according to graphic symbols, and the corresponding dot matrix code (glyph code) is obtained.
GB1616.h//------------------ Chinese character font data structure definition ------------------------//structtypFNT_GB16 //Chinese character font data structure {unsignedcharIndex[3]; //Chinese character internal code index unsignedchar Msk[32];//dot matrix code data };
//////////////////////////////////////////////////////////////////////////////// Chinese character font table//// Chinese character library: Song Dynasty 16.dot, horizontally modulo left high bit, data arrangement: from left to right, from top to bottom///////////////////////////////////////////////////////////////////////////////////conststructtypFNT_GB16 codeGB_16[]= //data table{/*---------------------------------------------------------------------------------;source file/text :Xu;width×height (pixels):16×16--------------------------------------------------------------------------------*/"Xu",0x10,0x80,0x10,0x80,0x21 ,0x40,0x42,0x20,0x94,0x10,0x1B,0xEC,0x20,0x80,0x60,0x80,0xAF,0xF8,0x 20,0x80,0x22,0xA0,0x24,0x90,0x2A,0x88,0x21,0x00,0x00,0x00,0x00,0x00, This structure is very simple: one is the internal code, and one is the dot matrix sequence. The previous dot matrix library was placed in the order of the internal code, and no internal code index was needed. If only some Chinese characters were placed, the internal code index was needed. (The Chinese character "Xu" in the front is to find the dot matrix sequence of the word when outputting "Xu". This dot matrix sequence is written by myself. When displayed with 1602, because the chip has an English dot matrix sequence in the memory, there is no need to write it.) Generally, two bytes are enough for the internal code. If you use one more byte, you just add a trailing 0. In this way, the Chinese character string can be directly placed in the Chinese character internal code;
13. 12864 LCD:
Each display point corresponds to a binary number, 1 means on, 0 means off. The RAM that stores these dot matrix information is called display data memory. To display a certain graphic or Chinese character is to write the corresponding dot matrix information into the corresponding storage unit.
The address counter (AC) of the graphics RAM will only automatically increment the horizontal address (X axis) by one. When the horizontal address = 0FH, it will be reset to 00H. However, it will not automatically increment the vertical address with a carry. Therefore, when multiple data are written continuously, the program needs to determine whether the vertical address needs to be reset.
The drawing display RAM provides 128×8 bytes of memory space. When changing the drawing RAM, first write the horizontal and vertical coordinate values continuously, and then write two bytes of data to the drawing RAM. The address counter (AC) will automatically increase the horizontal address (X address) by one. When the horizontal address is 0XFH, it will be reset to 00H; the vertical address will not be automatically incremented by 1. The drawing display must be turned off during writing to drawing RAM,
[cpp] view plain copy//Display Chinese characters voiddispString (uchar X, Y,uchar *msg)//Which row is X and which column is Y. msg is Chinese characters {if(X==0) write_data(*msg++); //Display Chinese characters }}////////////////////////////////// //////////////// ////////////////// Display image voiddisppicture(uchar code *adder){ uint i,j;//*******Display the upper half screen content settings for(i=0;i<32;i++)//32 column addresses in the upper half of the screen { write_com(0x80 + i);//SET vertical address VERTICALADD write_com(0x80);//SET horizontal address HORIZONTAL ADDfor(j=0;j<16;j++) { write_data(*adder); adder++; }}//************Display content settings in the lower half of the screen for(i=0;i<32;i++) //{ write_com(0x80 + i); //SET vertical address VERTICALADD write_com(0x88); //SET horizontal address HORIZONTAL ADDfor(j=0;j<16;j++){write_data(*adder);adder++;} }} For C language, space is automatically allocated for a defined variable, and its address is the name of the variable. Through this name, the data can be retrieved in the memory and new data can be obtained through calculation. However, in assembly, the programmer needs to define the storage space and send the data to the accumulator for calculation. Every step requires the programmer's operation. In C language, these processes are completed by the compiler.
①. How is the memory allocation of variables carried out in microcontroller C language? Could it be that the compiler intelligently adds allocation and recycling code during the compilation process? The key point is that the program I made, how can I ensure that it does not have memory overflow errors? If I'm doing a recursive operation, then the memory requirements are difficult to calculate by myself.
If there are too many variables, the compiler will prompt that the data segment is too large. To ensure that there is no memory overflow error, the main consideration is whether the stack overflows, and it depends on experience.
The microcontroller can define bit variables, but it cannot define bit arrays. Writing in C language seems simple, but actually generates the largest amount of code. The microcontroller used for control hardly uses floating point operations, which is not only slow but troublesome and takes up space. If it is a DSP chip, it will be much better if it has a suitable hardware structure.
Company phone number: +86-0755-83044319
Fax/FAX: +86-0755-83975897
Email: 1615456225@qq.com
QQ: 3518641314 Manager Li
QQ: 332496225 Manager Qiu
Address: Room 809, Building C, Zhantao Technology Building, No. 1079 Minzhi Avenue, Longhua New District, Shenzhen
Related Recommendations
Song Yuanming's Speech at Huaqiang Lecture: The Path to Global Branding for Kinghelm and Slkor
2026-06-05
691
After Two Consecutive Titles, We Are Still making progress——Slkor Interview with Sun Gaofei
2026-06-11
454
Tens of Thousands of Enterprises Choose Chinese Brands – Kinghelm and Slkor Are Selling Well Worldwide!
2026-06-24
443
粤公网安备44030002007346号