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Cooper Bussmann Wireless Ethernet & Device Server BU-945U-E 802.11 DSSS User Manual
3A1582Rev1.6
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 BU-945U-E makes this possible by internally performing the necessary protocol conversion. The conversion is always performed by the
BU-945U-E which is directly connected to the Modbus serial device (i.e., only this module needs to have Modbus TCP to RTU Gateway enabled).
The above example demonstrates how a Modbus/TCP Client (Master) can connect to one or more Modbus RTU (i.e., serial) Slaves.In this example
the BU-945U-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 BU-945U-E within the configured Response Timeout, the BU-945U-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.
Serial Menu
RS232 / 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 110bps to a maximum of 115,200bps.
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.
Local IP Address Select the IP address of the PPP server. The remote device may be made visible on the Ethernet or
Wireless networks by either utilizing proxy-arp or routing.The proxy-arp feature may be enabled by
setting the Local IP address the same as the Ethernet IP Address or the Wireless IP Address.The module
will respond on behalf of the remote device, making it seem like the device is present on the configured
network.Alternatively, if the IP address selected is not the same as the Ethernet or Wireless IP address,
routing is used to pass data to the Ethernet and Wireless ports.
Remote Device IP Address Select the IP address of the remote device. Ensure this address is not the same as any other device on
the Ethernet or Wireless networks.