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245U-E Wireless Ethernet Modem User Manual
49
Rev Version 2.24
Modbus TCP to RTU Gateway
The Modbus TCP to RTU gateway allows an Ethernet Modbus/TCP client (master) to communicate with a
serial Modbus RTU slave. The 245U-E makes this possible by internally performing the necessary protocol
conversion. The conversion is always performed by the 245U-E which is directly connected to the Modbus
serial device, only this module needs to have Modbus TCP to RTU gateway enabled.
Figure 41
Modbus/TCP Client to Modbus RTU Slaves
The above example demonstrates how a Modbus/TCP client (master) can connect to one or more Modbus
RTU (serial) slaves. In this example, the 245U-E access point is configured with the “RS232 Modbus/TCP to
RTU Gateway” enabled. Once enabled, the gateway converts the Modbus/TCP queries received from the
master into Modbus RTU queries and forwards these over the RS232 port to the slave. When the serial
response to the query arrives from the slave, it is converted to a Modbus/TCP response and forwarded
via the network to the Modbus/TCP master. If no response was received serially by the 245U-E within the
configured Response Timeout, the 245U-E will initiate a number of retries specified by the configured
Maximum Request Retries.
The Modbus TCP to RTU gateway may be configured to operate on either the RS 232 or RS 485 port.
3.12 Serial Menu
RS-232 / RS485 Serial Port Configuration
RS232 Port
Select the desired functionality. Select either PPP, Serial Gateway or Modbus
TCP to RTU.
Data Rate
The serial data rate desired. Serial data rates available range from 110 bps to a
maximum of 115,200 bps.
Data Format
The data format desired. All the standard data formats are supported.
Flow Control
Selects CTS/RTS or None.
RS232 PPP Server (Only RS232)
Username
User name to enter to access RS-232 PPP server.
Password
Password to access RS-232 PPP server.