Prosoft-technology MVI46-MCM Manual do Utilizador descarregar pdf (Página 60)

Reference MVI46-MCM ♦ SLC Platform

User Manual Modbus Communication Module

Page 60 of 108 ProSoft Technology, Inc.

March 29, 2011

5.2 Functional Overview

5.2.1 About the MODBUS Protocol

MODBUS is a widely-used protocol originally developed by Modicon in 1978.

Since that time, the protocol has been adopted as a standard throughout the

automation industry.

The original MODBUS specification uses a serial connection to communicate

commands and data between Master and Slave devices on a network. Later

enhancements to the protocol allow communication over other types of networks.

MODBUS is a Master/Slave protocol. The Master establishes a connection to the

remote Slave. When the connection is established, the Master sends the

MODBUS commands to the Slave. The MVI46-MCM module can work as a

Master and as a Slave.

The MVI46-MCM module also works as an input/output module between itself

and the Rockwell Automation backplane and processor. The module uses an

internal database to pass data and commands between the processor and

Master and Slave devices on MODBUS networks.

5.2.2 General Concepts

The following topics describe several concepts that are important for

understanding the operation of the MVI46-MCM module.

1 On power up the module begins performing the following logical functions:

2 Initialize hardware components

o Initialize SLC backplane driver

o Test and Clear all RAM

o Initialize the serial communication ports

3 Wait for module configuration from the SLC processor

4 Allocate and initialize Module Register space

5 Enable Slave Driver on selected ports

6 Enable Master Driver on selected port if configured

After the module has received the Module Configuration, the module will begin

communicating with other nodes on the network, depending on the configuration.

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Prosoft-technology MVI46-MCM Manual do Utilizador Página 60