Siemens SIMATIC ET 200SP F-TM Equipment Manual page 38

Selection
The STO safety function is always enabled and cannot be disabled via parameter
assignment.
You can select the STO function via the fail-safe digital input at STO+ and STO- terminals.
The selection of the STO function is enabled directly as a response to safety messages (e.g.
when a defect is detected in a monitoring channel).
Range of application
You can use the STO safety function without any restrictions. A special encoder concept
suitable for safety is not required.
Applications
Application areas are all machines or systems with moving axes (e.g. conveyor systems,
handling systems).
STO can be used in which the motor is already at a standstill or comes to a standstill safely
due to friction in a short time.
STO allows safe working while a protective door is open. A conventional Emergency Stop
with electromechanical unlocking is not required. The converter remains connected to the
supply system and has full diagnostics capability.
Note
Difference between EMERGENCY OFF and EMERGENCY STOP
EMERGENCY OFF and EMERGENCY STOP are commands that mitigate different risks in
the machine or plant. The STO function is suitable for implementing an EMERGENCY
STOP, but not an EMERGENCY OFF.
F-TM ServoDrive
Equipment Manual, 02/2020, A5E47579503-AA
Safety functions integrated in the drive
5.1 Basic safety information
37