How the microprocessor is defined in the CPU

Since the invention of the transistor in human 1947span> years, more than 50 years of semiconductor technology experienced silicon transistors, integrated circuits, VLSI, very large scale integrated circuits and other generations, the rapid development of other industries are not. Semiconductor technology has a wide impact on society as a whole, so it is called "the seed of industry". CPU refers to the computer internal data processing and control of the processing process of the parts, with the rapid development of integrated circuit technology, chip integration density is more and more high, the CPU can be integrated in a semiconductor chip, the central processing unit functions of integrated circuit devices, is collectively known as "microprocessor ”。

Composition

The microprocessor consists of an arithmetic logic unit (alu,arithmetic Logical), an accumulator and a universal register set, a program counter (also called an instruction indicator), a timing and control logic component, a data and address latch/buffer, and an internal bus.

Arithmetic logic unit

Arithmetic logic unit Alu mainly completes arithmetic operation (+ 、-、 x, and comparison) and various logical operations (with, or, non, XOR, shift). The ALU is a combinational circuit, itself without the function of a storage operand, and must have two registers of the save operand: The Register TMP and the accumulator AC, the accumulator provides both the operands to the ALU and the result of the ALU's operation.

It must be pointed out that the microprocessor itself does not constitute a separate working system, nor can it execute the program independently, it must be equipped with a microprocessor storage, input to form a complete microcomputer to work independently.

Memory

A microcomputer's memory is used to store programs and data that are currently in use or frequently used. The memory is divided into random memory ram (Random Access Memory) and read only memory ROM (read only Memory) in read and write mode. Ram is also known as read/write memory, and the CPU can read or write its contents at any time as needed during the operation. RAM is a volatile memory, where its contents are lost after a power outage, allowing only temporary programs and data to be stored. ROM content can only read out can not write, power loss of its stored information remains unchanged, is non-volatile memory. So ROM is often used to store permanent parts of the program and data. such as initial seeker, monitoring program, basic input in operating system, bios of output management program, etc.

Input/output interface circuit (I/O interface)

The input/output interface circuit is an important component of a microcomputer. He is a microcomputer to connect external input, output equipment and a variety of control objects and information exchange with the outside of the logic control circuit. Because the peripheral structure, working speed, signal form and data format are different, so they can not be directly attached to the system bus, must use the input/output interface circuit to do intermediate conversion, in order to realize the exchange of information between the CPU. I/O interfaces are also known as I/O adapters, and different peripherals must be equipped with different I/O adapters. I/O interface circuit is an essential part of microcomputer application system. The development and design of any microcomputer application system is mainly the development and design of I/O interface.

Bus (buses)

Bus is a common channel of information transmission between components in a computer system, and it is an important component of microcomputers. It consists of several communication lines and a variety of three-state door devices which are actuated and isolated. The microcomputer is always used in the structure of the bus structure, that is, the composition of the computer components (microprocessors, memory, I/O interface circuits, etc.) between the connection through the bus, which is the unique structure of the microcomputer system. After the bus structure is adopted, the relationship between the functional components in the system is changed to the single relation of the components oriented to the bus. A part (function board/card) as long as the bus standards can be connected to the use of this bus standard system, so that the system function expansion or update easy, simple structure, reliability greatly improved.