Siemens SIMATIC S7-1200 - Page 1286

Communication processor and Modbus TCP
13.9 Legacy Modbus RTU communication (CM/CB 1241 only)
S7-1200 Programmable controller
1286 System Manual, V4.2, 09/2016, A5E02486680-AK
Network 3
: Move the first 3 words of the holding register data that has been read to some
other location, and set a DONE history bit. This network also sets an ERROR history bit and
saves the STATUS word to another location in the event of an error.
Network 4
: Write 64 bits of data from MW600-MW607 to output bit locations 00017 to 00081
on slave #2.
Network 5
: Set a DONE history bit when the write is complete. If an error occurs, the
program sets an ERROR history bit and saves the STATUS code.