Single-chip microcomputer is also called single-chip microcontroller. It is not a chip that completes a certain logic function, but integrates a computer system on a chip. It is equivalent to a miniature computer. Compared with a computer, the single-chip microcomputer only lacks I/O equipment. In a nutshell: a chip becomes a computer. Its small size, light weight and low price provide 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 principle and structure of the computer.
The application fields of single-chip microcomputers have been very extensive, such as smart meters, real-time industrial control, communication equipment, navigation systems, household appliances and so on.
Since the 1990s, the technology of single-chip microcomputer has been developed. With the progress of the times and the development of science and technology, the practical application of this technology has matured day by day, and the single-chip microcomputer has been widely used in various fields. Nowadays, people pay more and more attention to the development and application of single-chip microcomputer in intelligent electronic technology. The development of single-chip microcomputer has entered a new era. Whether it is automatic measurement or the practice of intelligent instrument, you can see the figure of single-chip technology. In the current industrial development process, the electronics industry belongs to a new industry. People successfully use electronic information technology in industrial production, which allows the integration of electronic information technology and single-chip microcomputer technology, which effectively improves the application effect of single-chip microcomputers. As a branch of computer technology, the application of single chip microcomputer technology in the field of electronic products enriches the functions of electronic products, provides a new way for the development and application of intelligent electronic equipment, and realizes the innovation and development of intelligent electronic equipment .
Single chip microcomputer is also called monolithic microcontroller, which belongs to a kind of integrated circuit chip. The single-chip microcomputer mainly includes CPU, read-only memory ROM and random access memory RAM, etc. The diversified data acquisition and control system allows the single-chip microcomputer to complete various complex operations, whether it is to control operation symbols or issue operation instructions to the system. Completed by the microcontroller. It can be seen that the single-chip microcomputer can be fully applied in intelligent electronic equipment by virtue of its powerful data processing technology and calculation function. Simply put, a single-chip microcomputer is a chip, which forms a system. Through the application of integrated circuit technology, data calculation and processing capabilities are integrated into the chip to achieve high-speed data processing.
basic structure
Arithmetic unit
The arithmetic unit is composed of arithmetic components-Arithmetic & Logical Unit (ALU), accumulators and registers. The function of the ALU is to perform arithmetic or logical operations on the incoming data. The input source is two 8-bit data, which come from the accumulator and the data register respectively. ALU can complete operations such as adding, subtracting, AND, OR, comparing the size of these two data, and finally storing the result in the accumulator.
The calculator has two functions:
(1) Perform various arithmetic operations.
(2) Perform various logic operations and conduct logic tests, such as zero value test or comparison of two values.
All operations performed by the arithmetic unit are directed by the 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 a program counter, an instruction register, an instruction decoder, a timing generator, and an operation controller. It is a “decision-making body” that issues orders, that is, coordinates and directs the operation of the entire microcomputer system. Its main functions are:
(1) Take an instruction from the memory and point out the location of the next instruction in the memory.
(2) Decode and test instructions, and generate corresponding operation control signals to facilitate the execution of prescribed actions.
(3) Command and control the direction of data flow between CPU, memory, and input and output devices.
The microprocessor interconnects the ALU, counter, register and control part through the internal bus, and connects with the external memory and input/output interface circuit 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
The accumulator A is the most frequently used register in the microprocessor. It has dual functions in arithmetic and logical operations: before the operation, it is used to save an operand; after the operation, it is used to save the result of the sum, difference or logical operation.
(2) Data register DR
Data register is a temporary storage unit that sends (writes) or fetches (read) data to memory and input/output devices through the data bus. It can save an instruction that is being decoded, it can also save a data byte that is being sent to the memory for storage, and so on.
(3) Instruction register IR and instruction decoder ID
Instructions include 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 the memory to the data register, and then transferred to the instruction register. When the system executes a given instruction, the operation code must be decoded to determine the required operation, and the instruction decoder is responsible for this work. Among them, 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 usually 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 that the current CPU wants to access. Due to the difference in speed between memory and CPU, address registers must be used to maintain address information until the memory read/write operation is completed.
Obviously, when the CPU stores data to the memory, the CPU accesses data from the internal memory, and the CPU reads instructions from the memory, address registers and data registers are all 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 the data register are also needed.
Hardware features
(1) The size of the single-chip microcomputer is relatively small, and the internal chip is used as a computer system. Its structure is simple, but the function is perfect, it is very convenient to use, and it can be modularized.
(2) The single-chip microcomputer has a high degree of integration and strong reliability. Even if the single-chip microcomputer is working for a long time, there will be no malfunction.
(3) The low voltage and low energy consumption of single-chip microcomputers are the first choice in people’s daily life, providing convenience for production and research and development.
(4) The single-chip microcomputer has strong data processing and computing capabilities, can be used in various environments, and has strong control capabilities