Siemens SINAMICS S120 Function Manual page 378

Safety Integrated basic functions
9.7 Control signals by way of terminals on the Control Unit and Motor/Power Module
Terminals for STO, SS1 (time-controlled), SBC
The functions are separately selected/deselected for each drive using two terminals.
● 1. Switch-off signal path (CU310/CU320)
Note
In a project with parallel power units and and enabled safety function STO, the following
occurs when firmware version 2.4 is converted to 2.5:
Parameters p9620[1] and p9620[2] are assigned the value "0" because firmware version
2.4 only contains parameter p9620[0]. Parameter p9620[0] contains the signal source for
power unit 1 and p9620[1] the signal source for power unit 2. This means that the STO
function for power unit 2 cannot be switched.
● 2. switch-off signal path (Motor Module/Power Module with CUA3x or CU310)
Both terminals must be operated simultaneously, otherwise a fault will be issued.
Figure 9-2 Terminals for "Safe Torque Off": example for Motor Modules Booksize and CU320
378
The desired input terminal is selected via BICO interconnection (BI: p9620[0]).
The input terminal is the "EP" ("Enable Pulses") terminal.
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
Drive functions