Siemens Sinamics S120 Function Manual page 477

Figure 9-2 Example: Terminals for "Safe Torque Off": example for Motor Modules Booksize and CU320-2
Grouping drives (not for CU310-2)
To ensure that the function works for more than one drive at the same time, the terminals for
the corresponding drives must be grouped together as follows:
1. Switch-off signal path
2. Switch-off signal path (Motor Module/Power Module with CUA3x)
Note
The grouping must be identical in both monitoring channels.
If a fault in a drive results in a "Safe Torque Off" (STO), this does not automatically mean
that the other drives in the same group also switch to "Safe Torque Off" (STO).
The assignment is checked during the test for the switch-off signal paths, The operator
selects "Safe Torque Off" for each group. The check is drive-specific.
Drive functions
Function Manual, (FH1), 01/2012, 6SL3097-4AB00-0BP2
9.8 Control via terminals on the Control Unit and Motor/Power Module
By connecting the binector input to the joint input terminal on the drives in one group.
By appropriately wiring the terminals for the individual Motor Modules/Power Modules,
belonging to the group, with CUA31/CUA32.
Safety Integrated basic functions
475