Automationdirect.com HX-ECOM Series - Network Server (Slave) Operation; Modbus Function Codes Supported; Determining the Modbus Address

Ethernet Communications Modules, 3rd Edition, Rev. D
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Chapter 5: MODBUS TCP for H0/H2/H4-ECOM100
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Network Server (Slave) Operation
This section describes how other Modbus TCP clients on a network can communicate with an
H0/H2/H4 -ECOM100 that you have configured for Modbus TCP protocol. A network client
must send a Modbus function code and Modbus address to specify a PLC memory location
the DL05/06/205/405 CPU. No CPU ladder logic is required to support Modbus TCP server
operation.
Modbus Function Codes Supported
The H0/H2/H4 -ECOM100 supports the following Modbus function codes when acting as a
Modbus TCP server.
Determining the Modbus Address
There are typically two ways that most Modbus addressing conventions allow you to specify a
PLC memory location. These are:
• By specifying the Modbus data type and address
• By specifying a Modbus address only.
Modbus
Function Code
Function
DL05/06/205/405
Data Types Available
01 Read Discrete Output Table Y, C, T, CT
02 Read Discrete Input Table X, SP
03
Read Holding registers (when addressing mode
is 584/984, this function is used to access
analog output registers)
V
04
Read Input Registers (when addressing mode is
584/984, this function is used to access analog
input registers)
V
05 Force Single Discrete Output Y, C, T, CT
06 Preset Single Holding Registers V
08 Loop Back / Maintenance
15 Force Multiple Discrete Outputs Y, C, T, CT
16 Preset Multiple Holding Registers
V