What is a microcontrollers?

Single-chip microcomputer (Microcontrollers) is an integrated circuit chip, which uses VLSI technology to integrate a central processing unit CPU with data processing capabilities, random access memory RAM, read-only memory ROM, various I/O ports and interrupt systems,  timers/counter functions (may also include display drive circuit, pulse width modulation circuit, analog multiplexer, A/D converter and other circuits) integrated into a silicon chip to form a small but complete microcomputer system, in the industry It is widely used in the field of control. From the 1980s, from the 4-bit and 8-bit single-chip microcomputers at that time, to the current 300M high-speed single-chip microcomputers.

Single-chip microcomputer (Microcontrollers) is an integrated circuit chip, which uses VLSI technology to integrate a central processing unit CPU with data processing capabilities, random access memory RAM, read-only memory ROM, various I/O ports and interrupt systems,  timers/counter functions (may also include display drive circuit, pulse width modulation circuit, analog multiplexer, A/D converter and other circuits) integrated into a silicon chip to form a small but complete microcomputer system, in the industry It is widely used in the field of control. From the 1980s, from the 4-bit and 8-bit single-chip microcomputers at that time, to the current 300M high-speed single-chip microcomputers.
Single-chip microcomputer, also known as single-chip microcontroller, is not a chip that completes a certain logic function, but integrates a computer system into a chip. It is equivalent to a microcomputer. Compared with computers, single-chip microcomputers only lack I/O devices. In a nutshell: a chip becomes a computer. Its small size, light weight and cheap price provide convenient conditions for learning, application and development. At the same time, learning to use single-chip microcomputers is the best choice for understanding computer principles and structures. Single-chip microcomputers have been used in a wide range of fields, such as smart instruments, real-time industrial control, communication equipment, navigation systems, and household appliances. Once a variety of products use single-chip microcomputers, they can upgrade the products. Adjectives are often added before the product names-"smart", such as smart washing machines.
Basic structure
Calculator

The arithmetic unit is composed of arithmetic components - arithmetic logic unit (Arithmetic & Logical Unit, referred to as ALU), accumulator and registers. The role of the ALU is to perform arithmetic or logic operations on the incoming data. The input source is two 8-bit data, which come from the accumulator and the data register respectively. The ALU can perform operations such as addition, subtraction, AND, or, and comparison of the two data, and finally store the result in the accumulator. For example, two numbers 6 and 7 are added. Before the addition, the operand 6 is placed in the accumulator, and the operand 7 is placed in the data register. When the addition instruction is executed, the ALU adds the two numbers and the result 13 Stored in the accumulator, replacing the original content of the accumulator 6.

The calculator has two functions:
(1) Perform various arithmetic operations.
(2) Perform various logical operations and perform logical tests, such as zero-value tests or comparisons of two values.
All operations performed by the arithmetic unit are commanded by control signals sent by the controller, and an arithmetic operation produces an operation result, and a logic operation produces a judgment.
Controller
The controller is composed of program counter, instruction register, instruction decoder, timing generator and operation controller, etc. It is the "decision-making mechanism" that issues commands, that is, coordinates and directs the operation of the entire microcomputer system. Its main functions are:

(1) Fetch an instruction from memory and indicate the location of the next instruction in memory.

(2) Decode and test the instructions, and generate corresponding operation control signals to facilitate the execution of prescribed actions.

(3) Command and control the direction of data flow between the CPU, memory, and input and output devices.
The microprocessor interconnects the ALU, counters, registers and control parts through the internal bus, and connects with the external memory and input and output interface circuits through the external bus. The external bus is also called the system bus, which is divided into data bus DB, address bus AB and control bus CB. Through the input and output interface circuit, realize the connection with various peripheral devices.
Main register
(1) Accumulator A
Figure 1-2 SCM block diagram
Accumulator A is the most frequently used register in a microprocessor. It has dual functions in arithmetic and logic operations: before the operation, it is used to save an operand; after the operation, it is used to save the obtained sum, difference or logical operation results.
(2) Data register DR
Data register is a temporary storage unit that sends (writes) or fetches (reads) data to memory and input/output devices through the data bus. It can hold an instruction being decoded, a byte of data being sent to memory for storage, and so on.
(3) Instruction register IR and instruction decoder ID
Instructions consist of opcodes and operands.
The instruction register is used to save an instruction currently being executed. When an instruction is executed, it is first fetched from memory into the data register and then transferred to the instruction register. When the system executes a given instruction, it must decode the opcode to determine the required operation, and the instruction decoder is responsible for this work. Wherein, the output of the opcode field in the instruction register is the input of the instruction decoder.

(4) Program counter PC
The PC is used to determine the address of the next instruction to ensure that the program can be executed continuously, so it is often called the instruction address counter. Before the program starts to execute, the memory unit address of the first instruction of the program (that is, the first address of the program) must be sent to the PC so that it always points to the address of the next instruction to be executed.

(5) Address register AR
The address register is used to save the address of the memory unit or I/O device to be accessed by the current CPU. Due to the difference in speed between the memory and the CPU, address registers must be used to hold address information until the memory read/write operation is complete.

Obviously, when the CPU stores data in the memory, the CPU fetches data from the memory, and the CPU reads instructions from the memory, the address register and the data register are used. Similarly, if the address of the peripheral device is viewed as a memory address unit, then when the CPU and the peripheral device exchange information, the address register and data register are also needed.

The development board is an embedded board used for R&D, research, and learning, and some products are made into boxes.

The core board refers to a module board that carries core chips and core services in a structure.

If you think the performance of a development board is good, it can be used as a core board, and a few peripherals around it or other small boards with low configuration and business focus are non-core boards. Only used to focus on doing business.

Development board is a general term for embedded boards; core board is the positioning of a module from a product perspective.

The single chip microcomputer is just a chip, and some peripheral circuits are needed to realize common functions.
MCU development board is a circuit board composed of MCU main chip plus some commonly used electronic devices, which is convenient for beginners to learn and experiment. The commonly used peripherals above are equipped with 6 or 8 LED lights, independent keys, matrix keys, LCD display or its interface string line EEPROM 24C02 stepper motor drive circuit relay infrared receiver etc.

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