1757-SRM 罗克韦尔AllenBradley 可配置流量计模块

1757-SRM 罗克韦尔AllenBradley 可配置流量计模块

PLC的基本组成

PLC基本组成包括中央处理器(CPU)、存储器、输入/输出接口(缩写为I/O，包括输入接口、输出接口、外部设备接口、扩展接口等)、外部设备编程器及电源模块组成，见图1。PLC内部各组成单元之间通过电源总线、控制总线、地址总线和数据总线连接，外部则根据实际控制对象配置相应设备与控制装置构成PLC控制系统。

中央处理器

中央处理器(CPU)由控制器、运算器和寄存器组成并集成在一个芯片内。CPU通过数据总线总线、地址总线、控制总线和电源总线与存储器、输入输出接口、编程器和电源相连接。

小型PLC的CPU采用8位或16位微处理器或单片机，如8031、M68000等，这类芯片价格很低；中型PLC的CPU采用16位或32位微处理器或单片机，如8086、96系列单片机等，这类芯片主要特点是集成度高、运算速度快且可靠性高；而大型PLC则需采用高速位片式微处理器。

CPU按照PLC内系统程序赋予的功能指挥PLC控制系统完成各项工作任务。

The basic composition of PLC

The basic composition of PLC includes central processing unit (CPU), memory, input/output interface (abbreviated as I/O, including input interface, output interface, external device interface, expansion interface, etc.), external device programmer and power module, as shown in Figure 1. The internal components of the PLC are connected through the power bus, control bus, address bus and data bus, and the external devices and control devices are configured according to the actual control objects to constitute the PLC control system.

Central processing unit

The central processing unit (CPU) consists of a controller, an arithmetic unit, and registers and is integrated into a single chip. The CPU is connected to the memory, input/output interface, programmer, and power supply through the data bus, address bus, control bus, and power supply bus.

The CPU of small PLC uses 8-bit or 16-bit microprocessor or single-chip microcomputer, such as 8031, M68000, etc., and the price of such chips is very low; The CPU of medium-sized PLC adopts 16-bit or 32-bit microprocessor or single-chip microcomputer, such as 8086, 96 series single-chip microcomputer, etc., the main features of this kind of chip are high integration, fast computing speed and high reliability; Large PLCS require high-speed bit-chip microprocessors.

The CPU commands the PLC control system to complete various tasks according to the function given by the system program in the PLC.