Operating Spanner Modules at Modbus TCP
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In the ”Modbus TCP Slave I/O Mapping” tab, change the value of the “Always Update Variables”
drop down box to “Enabled 2 (Always in Bus Cycle)”.
Click “Online”
“Login” and download the program to the TX507.
Follow the prompts.
Fig. 34: CODESYS – update variables
NOTE
If the PLC supports the function, it is reasonable to use Function Code FC23
„read/write multiple register“ in order to read or write all of the 240 data words in one
channel. The read-write access should start at the beginning of the data segment to be
read or written in order to guarantee a consistent data transmission between PLCs. It is up
to the user to test data transfer consistency when multiple blocks of I/O data are read from
and written to a single spanner port.
