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Cooper Bussmann 945U-E Wireless Ethernet Modem & Device Server User Manual
Rev Version 2.14
Registers
Purpose
4376
TCP-RTU Modbus server connection status inverted.
4377
Multicast pipe connection status inverted.
4378–4999
Reserved for future use.
Modbus TCP client (master) enables the 945U-E to connect to one or more Modbus TCP servers (slaves). All
Modbus master messages are directed to/from the onboard I/O registers, depending on configuration (described
below). The Modbus TCP client may also poll Modbus RTU (serial) devices connected to either the local serial port
or a remote 945U-E serial port by enabling the Modbus TCP to RTU gateway at the corresponding serial port (see
“3.10 Serial Port Configuration”).
Modbus TCP client functionality allows a maximum of 100 mappings to be configured and a maximum of
25 different Modbus TCP servers. Modbus TCP server (slave) enables the 945U-E to accept connections from one
or more Modbus TCP clients (masters).
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) than the onboard Modbus TCP server.
Up to 32 separate connections to the Modbus TCP server are supported.
Figure 40 Modbus TCP
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 945U-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 to the device ID of the onboard Modbus TCP
server of the 945U-E to which the serial device is connected.
The 945U-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 and from a given register has not
been completed for longer than a configurable timeout, the value of that register will be reset to zero.