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3.13.3 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 XYR 400E makes this possible by internally
performing the necessary protocol conversion. The conversion is always performed by the XYR
400E 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 XYR 400E 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 XYR 400E within the configured Response Timeout, the
XYR 400E 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. It does not support operation on both ports at the same time.
Enable RS-232 Modbus
TCP to RTU Gateway
Enable RS-485 Modbus
TCP to RTU Gateway
Data Rate
Data Bits Parity Stop Bits
Pause Between Requests
Response Timeout
Connection Timeout
Maximum Request Retries
Maximum Connections
Version 1
5/1/08
Client
LAN
Modbus/TCP Client
(Master)
Check this box to enable the Modbus TCP to RTU Gateway on the RS-
232 port. Only a single serial port is allowed at a time.
Check this box to enable the Modbus TCP to RTU Gateway on the RS-
485 port. Only a single serial port is allowed at a time.
The serial data rate desired. Serial data rates available range from
110bps to a maximum of 115,200bps.
The data format desired. Data formats of 8N1, 7E1, 7O1, 7E2, 7O2 are
supported.
Enter the delay between serial request retries in milliseconds
Enter the serial response timeout in milliseconds – a serial retry will be
sent if a response is not received within this timeout.
Enter the TCP connection timeout in seconds – if no Modbus/TCP data
is received within this timeout then the TCP connection will be
dropped. Set this field to zero for no timeout.
Enter the maximum number of request retries performed serially.
Enter the maximum number of simultaneous TCP connections to the
server allowed.
XYR400E Ethernet Modem
Access
Point
RS232
Modbus RTU
Slave
RS232
Modbus/TCP to
RTU Server
54
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