Figure 36 - Modbus Master - Elpro Technologies 915U-2 User Manual

Page 60 915U-2 Wireless I/O
onboard Modbus TCP Server. Up to 32 separate connections to the Modbus TCP
Server are supported.
Modbus TCP Client (Modbus Master) enables the 915U-2 to connect to one or more
Modbus TCP Servers (Slaves).
All Modbus Master Messages are directed either to/from the onboard I/O registers
depending on configuration (described below). The Modbus TCP Client may also poll
Modbus TCP (Ethernet) and Modbus RTU (serial) devices connected to either the local
module or a remote 915U-2 module. This is done by enabling the Modbus TCP to RTU
gateway at the corresponding serial port
Modbus TCP Client functionality allows connections to a maximum of 24 different
Modbus TCP Servers and up to 100 mappings can be configured.
The screen shot below shows an example of Modbus Client Mappings.

Figure 36 - Modbus Master

In the example above the first mapping shows the Modbus Client (Master) is configured
to read analog values from a device connected on the LAN. The mappings function
code is "Read" and is reading a count of 4 values (Analogs) from the Ethernet address
192,168.0.10, Device ID #10, starting at address 30001, and then writing these values
into its own local registers starting at 40501. The server Port is 502, which is a standard
Modbus TCP Port address.
The next mapping shows something similar however, instead of analog value they are
digital values. The Function code is "Read" again from IP address 192.168.0.10 and
Device ID #10. It will read 8 values starting from address 10001 and writing them to the
local address starting at 501.
The third mapping is similar to the second however, instead of reading from an Ethernet
device it will read from a Serial device connected to the local RS485 port.
Mapping shows a function code "Read" from Device ID #5 connected to the Localhost
IP address 127.0.0.1 (*Note) It is reading 8 values from address 10001 and then writing
these values to local register 509.
The last mapping shows the Modbus Client can also write values to Modbus devices
either on serial or TCP. This mapping is setup to "Write" with an I/O Count of 8 from the
local address 10501 to Device 10 on Server IP address 192.168.0.10 at address
location 4.
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