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Cooper Bussmann 945U-E Wireless Ethernet Modem & Device Server User Manual
Rev Version 2.14
The second mapping reads 8 registers from serial unit D into onboard registers in unit B. Note that in this case the
specified Device ID 6 is the Modbus address of the serial device D, while the Server IP Address 192.168.0.200 is
the IP address of unit C since the Modbus TCP to RTU gateway at unit C converts the Modbus TCP message to
Modbus RTU and routes it out the serial port to unit D.
The third mapping takes the 8 registers read by the second mapping and writes them to the serial unit A. The
specified Device ID 5 is the Modbus Address of the serial device A, and the Server IP Address 192.168.0.196 is the
IP Address of the local unit B since the local Modbus TCP to RTU Gateway is to route the message out the serial
port to unit A.
Since the 945U-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 which could, for example, be exploited by a central
monitoring facility or SCADA.
Modbus TCP Configuration on I/O Transfer Menu
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/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.
Enable Modbus
Statistics
Enables the Modbus Diagnostic registers, as shown in “4.9 Internal Diagnostic
Modbus Registers.” Disabling this option will free up the registers and also slightly
increase processing resources.
Log background
Noise
RSSI & BGND on RX messages are made available in the diagnostic registers (see
“4.9 Internal Diagnostic Modbus Registers” for details). For a hexadecimal value
of 5F5D the 5D byte = RSSI and the 5F byte = BGND. Convert the value from
hexadecimal to decimal and add a “-” (for example, 5F = -95dB). Enabling this option
removes the background noise byte from these registers and therefore only the RSSI
value is made available.
Modbus TCP Client Mappings on I/O Transfer Menu
Local Register
Enter the starting onboard I/O register number that the specified Modbus master
transaction will transfer I/O to/from.
I/O Count
Specify the number of consecutive I/O register to be transferred for the specified
transaction.
Function Code
Specify the Modbus function code for the transaction.
Destination Register
Enter the starting I/O register number in the destination device that the specified
Modbus master transaction will transfer I/O to/from.
Device ID
Enter the Modbus device ID of the destination Modbus device.
Server IP Address
Specify the IP address of the destination Modbus TCP server for the specified
transaction.