Advantech EKI-1122L Manual de usuario descargar pdf (Pagina 11)

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IPC Chassis

Video Surveillance

Serial Comm. Cards

Device Servers

Display Solutions

Panel Computers

Fanless Panel PCs

Operator Panels

Industrial Motherboards

Embedded IPCs

Mobile Computers

IPC Peripherals

DAQ

Ethernet Switches

Signal Conditioning

USB DAQ

SBCs and Backplanes

Pre-Conﬁgured Systems

Modbus Gateway Solutions

Introduction

Ethernet networks have become increasingly vital for industrial automation applications. Many control devices today do not have an Ethernet port and can only communicate with a

dedicated local PC or control panel. Advantech’s revolutionary network-enabling technology is now allowing control devices with serial ports to connect to the Ethernet and share

networks quickly and cost-effectively. The EKI-1221 and EKI-1222 are network-based, Modbus Gateways for integrating new and existing Modbus/RTU or Modbus/ASCII serial devices

to newer Modbus/TCP networked-based devices. Manufacturers, system integrators, and end users can now take advantages of the EKI-1221 and EKI-1222 to create networked

applications for remote managing and accessing data for control devices that was not possible before.

Modbus Protocol

Originally developed for PLCs in automation and manufacturing control applications, Modbus has become one of the most popular open standard protocols worldwide. When it

comes to planning data communications for open, multi-vendor industrial control systems, Modbus is the ﬁrst choice of end-users and system integrators alike. Although it is not

the most powerful protocol available, its rare simplicity allows not only rapid implementation, but also remains ﬂexible enough to be applied in virtually all industrial situations. The

communication modes of Modbus include ASCII, RTU or TCP/IP. The EKI-1221 and EKI-1222 are used to support applications such as protocol conversion between serial (Modbus/

ASCII or Modbus/RTU) and networked (Modbus/TCP) Modbus devices or it can be used to bridge Modbus serial devices over Ethernet TCP/IP network.

The Modbus/RTU and Modbus/ASCII protocols deﬁne how a “master” device polls one or more “slave” devices to read and write real-time data over RS-232, RS-422, or RS-485

serial data communication.

During Modbus network communications, the protocol determines how each controller will know its device address, recognize a message addressed to it, determine the kind of action to

be taken, and extract any data or other information contained in the message. If a reply is required, the controller will construct the reply message and send it back using Modbus protocol.

The way controllers communicate with each other is by using a master-slave technique, in which only one device (the master) can initiate queries. The other devices (slaves) respond

by supplying the requested data to the master, or by taking the action requested in the query. Typical master device includes host processors and programming panels. Typical slaves

include programmable controllers.

The master can address individual slaves and initiate a broadcast message to all slaves. On the other hand, slaves return a response to queries that are addressed to them individually.

Responses are not returned to broadcast queries from the master.

The Modbus protocol has a deﬁnite format for the master’s query, which incorporates the device address, a function code deﬁning the requested action, any data to be sent, and an

error-checking ﬁeld. The slave’s response message, which is also constructed using Modbus protocol, contains ﬁelds conﬁrming the action taken, any data to be returned, and an

error-checking ﬁeld. If an error occurred in receipt of the message, or if the slave is unable to perform the requested action, the slave will construct an error message and send it as

its response.

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