4-3
IM 04L51B01-01EN
Using Modbus Functions (Communicating with Modbus devices)
4
4.2 UsingModbus/TCPtoEnabletheGX/GPto
Read Data from and Write Data to Other Devices
(Modbusclientfunction)
The Modbus function is used by the GX/GP and external Modbus devices to perform
communication and data reading and writing.
The GX/GP can operate as a Modbus client. The maximum number of connectable servers
is 16 for the GX20-1/GP20-1/GX10/GP10 and 32 for the GX20-2/GP20-2.
The GX/GP can connect to another device (Modbus server) via Modbus/TCP and read from
and write to the device’s internal registers. Read data can be handled using communication
channels. Data that can be written are I/O channel data, math channel data, and
communication channel data.
Modbus server
Modbus client
Ethernet
GX/GP
Command
Input register
Hold register
Read
Write
Read
3XXXXX
4XXXXX
Write
Read
Read
Server device internal register
GX/GP
4.2.1 SettingBasicNetworkCommunicationConditions
Description
• ObtaintheIPaddressautomatically
• SettheIPaddressmanually(whenautomaticIPaddressassignmentisset
toOff)
For details on the settings, see page 1-143 in section 1.17.1, “Setting Basic Communication
Conditions”.
4.2.2 Configuring the Modbus Client Function
Description
• EnabletheModbusclientfunction
• Setthecommunicationinterval
• Settherecoveryaction
• Setthekeepconnectionfunction
For details on the settings, see “Configuring Basic settings” page 1-152 in section 1.17.6,
“Configuring the Modbus Client Function (/MC option)”.