Siemens SIMATIC ET 200AL System Manual page 205

Safety-related shutdown of ET 200AL IO-Link modules
Block diagram
① 5-wire cable for a Port Class B connection
② 3-wire cable for a Port Class A connection
Figure A-1 Higher-level safety circuit of the outputs
Note potential groups for safety-related shutdown
When a digital output is connected to a digital input, pay attention to the potential groups.
Depending on the configuration, 1M and 2M can be connected through this, which leads to
cancellation of the electrical isolation between 1L+ and 2L+.
The safety-related shutdown is not permitted if the electrical isolation is canceled.
62
WARNING
IO-Link I/O modules
System Manual, 08/2021, A5E48755395-AB