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245U-E Wireless Ethernet Modem User Manual
Rev Version 2.24
mappings directed at any server. The “Reset Registers on Comms Fail” option is enabled with a timeout of
60 seconds, indicating that any of the registers at unit B will be reset if a successful Modbus transaction
involving that register has not been executed in the last 60 seconds.
Since the 245U-E supports Modbus TCP client and server simultaneously, the Modbus TCP server for unit
B above could also be enabled. This would allow one (or more) external Modbus TCP clients anywhere on
the extended wired or wireless network to connect to unit B and monitor the status of the I/O registers,
including the I/O at units A, C, and D. This is a very powerful and flexible feature that could, for example, be
exploited by a central monitoring facility or SCADA.
Figure 48
TCP Client Configuration
Modbus TCP Configuration on I/O Transfer Menu
The following table describes the settings shown in Figure 48.
Enable Modbus TCP
Server (Slave)
Select this checkbox to enable the onboard Modbus TCP server. All Modbus
TCP connections to the module IP address and specified Modbus server device
ID will be routed to the onboard I/O registers.
Modbus Server Device
ID
Specify the Modbus device ID for the onboard Modbus TCP server. Allowed
values are 0 to 255.
Enable Modbus TCP
Client (Master)
Select this checkbox to enable the onboard Modbus TCP client. I/O to be
transferred via the Modbus TCP client is specified with Modbus TCP client
mappings.
Modbus Client Scan
Rate
Enter the delay (in milliseconds) between execution of consecutive Modbus
TCP client mappings to the same server.
Reset Registers on
Comms Fail
When enabled, the value in any onboard I/O register will be reset to zero if a
valid Modbus transaction directed to or from the given register has not been
completed for longer than the Comms Fail Timeout.
Comms Fail Timeout
The period of time after which onboard I/O registers will be reset if a valid
Modbus transaction directed at that register has not completed.