Chapter 2. programming interface, Overview, Modbus master requirements – Comtrol Modbus TCP User Guide User Manual
Page 17: Programming interface
DeviceMaster UP Modbus/TCP User Guide: 2000447 Rev. I
Chapter 2. Programming Interface - 17
Chapter 2. Programming Interface
2.1. Overview
The DeviceMaster UP provides highly flexible Modbus connectivity.
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Modbus masters supported include Modbus/TCP and Modbus/RTU and Modbus/ASCII serial masters.
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Both serial Modbus/RTU and Modbus/ASCII slave devices are supported.
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All Modbus masters can communicate with all Modbus slave devices.
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The Modbus/RTU and Modbus/ASCII Protocol Interface is defined in (
ASCII To-Slaves Protocol Interface
The DeviceMaster UP provides highly advanced raw/ASCII device functionality:
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Both serial and Ethernet TCP/IP devices are supported.
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Modbus interfaces include Modbus/TCP masters, Modbus/TCP slaves, and both Modbus/RTU and
Modbus/ASCII serial masters.
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Up to six Ethernet TCP/IP Application connections per serial or Ethernet TCP/IP device.
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The raw/ASCII interface is defined in (
You must configure the DeviceMaster UP through its embedded web pages defined in
The DeviceMaster UP uses normal Modbus addressing conventions and provides receive, transmit, and
statistical data.
Appendix A. Programming the PLC via Concept
on Page 85 describes the Concept
™
PLC programming
examples provided with the DeviceMaster UP. It describes how to configure the DeviceMaster UP for raw
serial data and start running the example programs using the embedded web pages and the example PLC
program code.
Note: While the Concept PLC example programs directly apply only to the Schneider Electric Momentum,
Quantum, and Compact PLCs, they can be used as a guide for programming other PLCs.
2.1.1. Modbus Master Requirements
Modbus Masters (Modbus/TCP, Modbus/RTU serial, and Modbus/ASCII) must meet these requirements:
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The Modbus Master must support the corresponding protocol.
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For raw/ASCII data, the Modbus Master must support the Read Holding Registers and Write Multiple
Registers commands or, alternatively, the Read/Write Multiple Registers command.
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The Modbus Master must be able to write enough data in one message to handle the maximum sized
messages required for the serial or Ethernet device.