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Chapter 8. Modbus TCP Communication Functions
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Overview of Communications
This controller can communicate with a host unit such as a personal computer, PLC, or display unit using the
Modbus TCP protocol, which is compliant with Ethernet TCP/IP.
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Features
This controller's communication functions have the following features:
•
The host unit can communicate with this device using Ethernet by specifying the
IP address of this device.
•
Any desired communication data addresses can be set for almost all parameters
of this device. Communication data addresses are set at the factory for general
parameters that are used frequently, but they can be changed.
•
Communication data addresses can be set using the SLP-C7 Smart Loader
Package. Up to 200 communication data addresses can be set. They are used also
for Modbus RTU.
Handling Precautions
•
This device can be connected to three host communication units by Modbus
TCP. There are three usable connections. (In the same way, three Modbus TCP
connections are available when using Modbus RTU with RS-485.)
•
In the case of Modbus communications, the communication data address of
this controller that is set on the host unit may change to [host address -1] in a
communication message.
Example: If the communication data address is set to "1001" on the host unit, it
changes to "1000" in sent communication messages.
This device uses the communication data address specified in communication
messages for its send/receive processing.
Take the host unit's specifications into account when using this device.
•
Because data is not updated for up to 5 s after turning on or restarting this
controller, reading and writing of data by communication during this time will
not be reflected in the controller.
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Settings
For Modbus TCP communication, use the following settings.
Item
Initial value
IP address
192.168.255.254
Netmask
255.255.255.0
Default gateway
0.0.0.0
Modbus TCP port number
502
Handling Precautions
•
When the IP address, subnet mask, default gateway, or Modbus TCP port
number is changed, the setting is reflected from the next time the power is
turned ON. Turn the power off and then on again.