来源： 作者： 发布时间：2020-05-14

 

 现实世界中的设备到设备过程自动化通信

In the real world of the device to device process automation communication

在许多情况下，设备间的对话或会话，会系统化地

a dialogue or conversation between devices occurs systematically in many cases

在不同类型的通信网络上，以不同的语言出现

over different types of communication networks, and in different languages

不同的过程自动化设备厂商

Depending on the process automation equipment manufacturer

会使用非常特定或专有的语言

a very specific or proprietary language is used

或可能是通常对行业开放的语言

or may be a language that is commonly open to the industry

正是这些开放协议，使得很多厂商

It is these open protocols many manufacturers adapt

在市场上能够轻松地集成他们的产品

to easily integrate their products in a market

“开放协议”意味着规范已经发布

An Open Protocol means the specifications are published

任何人都可以自由或通过授权使用

and may be used by anyone freely or by license

开放协议通常由公司、用户组

Open protocols are usually backed by a combination of corporations

专业协会和政府共同

user groups, professional societies, and governments

这为用户提供了更广泛的设备

This provides users with a much wider choice of devices

或系统选择用于满足特定的应用

or systems that can be utilized to meet specific applications

开放协议的优势包括多个制造商

Advantages of open protocols include support by multiple manufacturers

软件供应商、安装/服务组织和活跃的社区团体的支持

software vendors, and install/service organizations, active community groups

以支持在未来保持最新和添加功能的能力

for support the ability to stay current and add capabilities in the future

目前连接工业电子设备最常用的

One of the most common automation communication protocols

自动化通信协议之一是Modbus

of connecting industrial electronic devices used today is Modbus

在本课中，我们将讨论什么是Modbus通信协议

In this lesson, we will discuss what Modbus communication protocol is

以及行业中使用的Modbus通信类型

and the types of Modbus communication used in the industry

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在过程自动化和SCADA(监控和数据采集)领域

The Modbus communication protocol is the oldest

Modbus通信协议是最早的

and by far the most popular automation protocol in the field of

并且到目前为止最常用的自动化协议

process automation and SCADA (Supervisory Control and Data Acquisition)

了解如何建立基于Modbus的网络

Knowing how to create Modbus based networks is essential

对于工作在这些领域的任何一个电气技师和工程师都是必修课

for any electrical technician and engineer working in these occupation fields

能够集成不同厂家的设备

Being able to integrate devices from different manufacturers

是一项很受欢迎的技能

is a skill that is in demand

也将最终让你在行业中更有价值更吃香

and will ultimately make you more valuable and marketable in the industry

Modbus是莫迪康在1979年发布的一个通信协议

Modbus is a communications protocol published by Modicon in 1979

用于它的可编程逻辑控制器或PLC

for use with its programmable logic controllers or PLCs

莫迪康现在是施耐德电气旗下的一个品牌

Modicon is now owned by Schneider Electric

Modbus为设备和设备之间的通信

Modbus provides common language for devices and equipment

提供了通用语言

to communicate with one another

例如，Modbus使得系统里

For example, Modbus enables devices on a system

连接到同一个网络，测量温度和湿度的设备

that measures temperature and humidity connected on the same network

能够将结果传送给监控计算机或PLC

to communicate the results to a supervisory computer or PLC

Modbus协议的开发和更新

And the development and update of Modbus protocols

已经由Modbus组织管理

have been managed by the Modbus Organization

Modbus组织是由兼容Modbus

The Modbus Organization is an association of users and suppliers

的设备用户和厂商组成

of Modbus-compliant devices

串行端口和以太网

Several versions of the Modbus protocol exist

有多个版本的Modbus协议，最常见的

for the serial port and Ethernet and the most common

是 Modbus RTU, Modbus ASCII, Modbus TCP和Modbus+

are Modbus RTU, Modbus ASCII, Modbus TCP and Modbus Plus

莫迪康发布了基于主从结构的

Modicon published the Modbus communication interface

多点网络的Modbus通信接口

for a multidrop network based on a master/slave architecture

Modbus节点之间的通信通过

Communication between the Modbus nodes is achieved

发送请求和读取响应类型的消息来实现

with send request and read response type messages

Modbus是描述消息通信对话的开放标准

Modbus is an open standard that describes the messaging communication dialog

Modbus通过几种物理介质进行通信

Modbus communicates over several types of physical media

例如串行RS-232、RS-485、RS-422以及以太网

such as serial RS-232, RS-485, RS-422 and over Ethernet

物理介质将在购买设备时选定

The physical media will be selected at the time when you purchase the devices

最初的Modbus接口运行在RS-232串行通信上

The original Modbus interface ran on RS-232 serial communication

但后来大多数的Modbus实施采用RS-485

But most of the later Modbus implementations use RS-485

因为它允许更长的距离、更高的速度

because it allowed longer distances, higher speeds

和在一个多点网络上使用多个设备的可能性

and the possibility of multiple devices on a single multi-drop network

通过串行RS-485物理介质的主从式Modbus通信

Master-Slave Modbus communication over serial RS-485 physical media

显示了两线传输和接收连接

showing two-wire transmit and receive connections

在诸如RS485或RS232的简单接口上

On simple interfaces like RS485 or RS232

Modbus消息以普通形式通过网络发送

the Modbus messages are sent in plain form over the network

网络将仅用于Modbus通信

and the network will be dedicated to only Modbus communication

但是，如果您的网络需要使用各类网络系统

However, if your network requires multiple heterogeneous devices

(如以太网上的TCP/IP)的多个不同类设备

using a more versatile network system like TCP/IP over ethernet

Modbus消息是以该物理接口规定的格式

the Modbus messages are embedded in Ethernet packets

嵌入以太网数据包中

with the format prescribed for this physical interface

因此在这种情况下，Modbus和其他类型的混合协议

So in this case, Modbus and other types of mixed protocols

可以同时存在于同一物理接口上

can co-exist at the same physical interface at the same time

Modbus的主要消息结构是点对点

The main Modbus message structure is peer-to-peer

Modbus可以在点对点和多点网络上运行

Modbus is able to function on both point-to-point and multidrop networks

Modbus设备使用主从(用于以太网的客户端-服务器)技术进行通信

Modbus devices communicate using a master-slave (client-server for Ethernet) technique

其中只有一个设备可以启动事件(称为查询)

in which only one device can initiate transactions (called queries)

其他设备通过向主设备提供请求的数据

The other devices respond by supplying the requested data to the master

或执行查询中请求的动作来响应

or by taking the action requested in the query

从设备是任何外围设备

A slave is any peripheral device

如I/O传感器、阀门、网络驱动器

such as an I/O transducer, valve, network drive,

或其他测量类型的设备

or other measuring types of devices which processes information

这些设备处理信息并使用Modbus将其响应信息发送到主设备

and sends its response message to the master using Modbus

主设备可以访问单个从设备

Masters can address individual slaves

或向所有从设备发起广播消息

or initiate a broadcast message to all slaves

从设备返回对单独发送给它们的，所有消息查询的响应

Slaves return a response to all message queries addressed to them individually

但不响应广播消息

but do not respond to broadcast messages

从设备不自行发起消息

Slaves do not initiate messages on their own

只响应从主机发送的消息查询

and only respond to message queries transmitted from the master

如果主设备发起了写命令

The master's query will consist of a slave address (or broadcast address)

它的查询将包括一个从设备地址(或广播地址)

a function code with a read or write data command to the slave

一个带有对从设备的读或写数据命令的功能代码

along with the write command data

以及写命令数据

if a write command was initiated by the master

和一个错误检查字段

and an error checking field

错误检查是主设备或从设备

The error checking is a value the master or slave creates

在传输或响应开始时创建的值

at the beginning of the transmission or response

然后在接收到消息时进行检查以验证内容是否正确

and then checked when the message is received to verify the contents are correct

从设备的响应包括确认接收到请求的字段

A slave's response consists of fields confirming it received the request

要返回的数据和错误检查数据

the data to be returned, and an error checking data

如果没有发生错误，从机的响应包含请求的数据

If no error occurs, the slave's response contains the data as requested

如果从设备接收到的消息查询出错

If an error occurs in the message query received by the slave

或者如果从机无法执行请求的动作

or if the slave is unable to perform the action requested

从设备将返回异常消息作为其响应

the slave will return an exception message as its response

从设备消息帧的错误检查字段

The error check field of the slave's message frame

允许主设备确认消息内容有效

allows the master to confirm that the contents of the message are valid

在本视频中，您了解了什么是Modbus通信协议

In this video you learned about what Modbus communication protocol is

以及行业中使用的Modbus通信类型

and the types of Modbus communication used in the industry

在下一个视频中，我们将讨论

In the next video, we will discuss the characteristics

Modbus通信协议如何在设备之间运行的特性

of how Modbus communication protocol works between devices

别换台！

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