DL205 User Manual, 4th Edition, Rev. D
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Chapter 4: System Design and Configuration
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Network Modbus RTU Master Operation (DL260 only)
This section describes how the DL260 can communicate on a Modbus RTU network as a
master using the MRX and MWX read/write instructions. These instructions allow you to
enter native Modbus addressing in your ladder logic program with no need to perform octal-
to-decimal conversions. Modbus is a single-master, multiple-slave network. The master is the
only member of the network that can initiate requests on the network. This section teaches you
how to design the required ladder logic for network master operation.
Modbus Function Codes Supported
The Modbus function code determines whether the access is a read or a write, and whether
to access a single data point or a group of them. The DL260 supports the Modbus function
codes described below.
Slave #1 Slave #3
Master
Modbus RTU Protocol
Slave #2
Modbus Function Code Function DL205 Data Types Available
01 Read a group of coils Y, C, T, CT
02 Read a group of inputs X, SP
05 Set / Reset a single coil (slave only) Y, C, T, CT
15 Set / Reset a group of coils Y, C, T, CT
03, 04 Read a value from one or more registers V
06 Write a value into a single register (slave only) V
07 Read Exception Status V
08 Diagnostics V
16 Write a value into a group of registers V
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