What is the difference between a single chip microcomputer and PLC? - PCB design

single chip microcomputer can replace PLC? The problem like flour can take the place of noodles, the answer is no. The first time I heard the answer may be a lot of people are in doubt, microcontroller clearly so powerful, rich function so why not replace PLC?

so today we will learn about the single chip microcomputer and PLC, respectively is what, what is the difference between between them.

a, microcontroller

single chip microcomputer ( 单片机) , which is also called the micro control unit ( 微控制器单元) , hereinafter referred to as MCU, is a kind of integrated circuit chips, is to use very large scale integrated circuit technology with data processing ability of the central processor ( 中央处理单元; CPU) , random access memory ( 随机存取存储器; RAM) , read-only memory ( 阅读- - - 只有记忆; ROM） , a variety of I/O mouth and interrupt system, timer/counter function (such as May include display driver circuit, pulse width modulation circuit, analog multiplexer and A/D converter circuit) Integrated into a silicon wafer that constitutes a small and perfect microcomputer system, it is widely used in various fields. Such as mobile phones, PC peripheral, remote controls, and automotive electronics, industrial stepper motor, the control of robotic arms, etc. , are visible to the MCU.

microcontroller in history is not long, but development is very rapid. Its generation and development and the production and the development of the microprocessor in sync, since 1971, the United States since Intel company first launched four microprocessors, its development so far can be roughly divided into five stages.

the early stages of MCU development ( From 1971 to 1976) In November 1971, Intel first design integration of 2000 transistors/piece of four Intel 4004 microprocessor, and is equipped with a RAM, ROM and shift register, constitutes the first MCS - 4 the microprocessor, then introduced a 8-bit microprocessor Intel 8008, and other companies launched 8 bit microprocessor.

low performance microcontroller stage ( From 1976 to 1980) : in 1976, Intel introduced the MCS - 48 series, represented by 8-bit CPU, 8 bits parallel I/O interface, 8 bit timer/counter, RAM and ROM, and integration in monolithic structure of a semiconductor chip, although the scope of its addressing co. , LTD. ( No more than 4 KB) , also do not have a serial I/O, RAM and ROM small capacity, interrupt system also relatively simple, but the function can meet the general industrial control and intelligent instruments, meters and other needs.

high performance MCU stage ( From 1980 to 1990) : this one phase of the high performance 8-bit microcontroller with serial port, a multilevel interrupt handling system, multiple 16-bit timer/counter. On chip RAM and ROM capacity increasing, and the addressing range of up to 64 KB, the individual chip with A/D conversion interface.

16 bit single chip stage ( From 1983 to 1989) : in 1983, Intel introduced the high performance 16-bit single chip microcomputer MCS - 96 series, due to its adopted the latest manufacturing technology, make the chip integration of 120000 transistors/piece.

all high level development stage ( 1990 - present) : so far, the single chip microcomputer from traditional 8-bit processor platform to senior 32-bit RISC processor platform change trend, but the 8-bit is still difficult to be replaced. 8-bit microcontroller cost is low, the price is cheap, easy to develop, its performance can meet the needs of most, only in the field of aerospace, automobile, such as robot technology, need high speed processing of large amounts of data, only need to choose a 16/32, but in the field of general industrial, eight general-purpose microcontroller, still is the most widely used microcontroller. SCM in integration, function, speed, reliability, application field, such as all-round development to a higher level.

the characteristics of the single chip microcomputer programming, maintenance is relatively complex, the commonly used C language or assembly language programming way, lower cost, the I/O interface is relatively limited.

2, PLC

PLC, the full name of Programmable Logic Controller, Programmable Logic Controller can be, is a specially designed for application in industrial environment and digital computing operations electronic systems. It USES a programmable memory, in its internal storage to perform logical operations, sequential control, timing, counting and arithmetic operations such as instruction, through digital or analog input/output control various types of machinery or production process.

three, why not replace PLC SCM (single chip micyoco)?

1。 Stability and reliability of

some say this is a fake problem, single chip microcomputer is components, PLC is made up of components as well as the large software system, the two are not comparable in this respect. There is nothing wrong with it, most of the PLC control chip is actually single-chip computer, that is to say, the PLC can be as a secondary development, SCM theory of single industrial protection grade, the stability of the single chip microcomputer and reliability than no PLC this type of products (IP67 To the IP letters, said the tag number contact protection and foreign body protection level, the second tag Numbers waterproof protection level) 。 And PLC which can deal with bad industrial environment of product also developed a redundant system. If stability and the reliability comparison is meaningless, then we will analysis from other aspects.