User manual

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Cooper Bussmann 245U-E Wireless Ethernet Modem & Device Server User Manual
49Rev Version 2.19
Figure 45 Modbus TCP
All Modbus transactions routed to the onboard Modbus TCP server are directed to and from the onboard general
purpose I/O registers. The Modbus TCP server is shared with the Modbus TCP to RTU gateway, so that the
Modbus device ID is used to determine if a Modbus transaction is to be routed to the onboard Modbus TCP server
or to a Modbus RTU device connected to the serial port. Care should be taken to ensure that all serially connected
Modbus devices use a different Modbus device ID (Modbus slave address) to the onboard Modbus TCP server. Up
to 32 separate connections to the Modbus TCP server are supported.
Modbus RTU (serial) master functionality is achieved by combining the Modbus TCP client (master) and Modbus
TCP to RTU gateway. Simply specify a Modbus TCP client (master) connection to a Modbus TCP server, where the
server is the address of any 245U-E with Modbus TCP to RTU gateway enabled. Care should be taken to ensure
that the device ID (Modbus address) of the serial device is different than the device ID of the onboard Modbus TCP
server of the 245U-E to which the serial device is connected.
The 245U-E provides a configurable option to automatically reset the value of the onboard I/O registers to zero in
the event of a communications failure. If a valid Modbus transaction directed to or from a given register has not
been completed for longer than a configurable timeout, the value of that register will be reset to zero.
The example shown in Figure 46 shows a typical Modbus setup. In this example the status of the onboard digital
input at B will be reflected at the onboard digital output at C. Also, eight single-bit registers from Modbus serial
device D will be transferred to A.
Figure 46 Modbus Setup