Siemens Simatic PCS 7 Function Manual page 77

Availability
If the active PROFIBUS DP fails, sensors and H system can communicate with each other
over the redundant bus connection. The configuration shown in the following figure provides
increased availability due to the redundant interfacing of the distributed I/O.
Additional information
● Section "How to configure redundant PROFIBUS DP (Page 119)"
● Manual
● Manual
High Availability Process Control Systems (V9.0)
Function Manual, 05/2017, A5E39221836-AA
SIMATIC Net PROFIBUS Networks
SIMATIC; Communication with SIMATIC
High availability solutions in PCS 7
4.3 Solutions for communication
77