Danfoss VLT FC 280 Operating Manual page 63

VLT® Midi Drive FC 280
Operating Guide
5 ms max. Test pulse
T37/38
STO request
state
STO valid
STO invalid
Illustration 33: Debouncing
6.4.3 Discrepancy Tolerance
The input signals at the 2 terminals may not always be synchronous. If the discrepancy between the 2 signals is longer than 0.5 s,
the STO fault warning (W252) occurs.
Input
signal
T37
T38
Discrepancy time
Illustration 34: Discrepancy Time
The discrepancy time does not extend the safety function's response time. The drive activates its safety function as soon as the
earlier valid signal arrives.
6.5 Safety Fieldbus
6.5.1 PROFIsafe
PROFIsafe is an additional safety protocol on top of a standard transmission system (PROFINET/PROFIBUS). PROFIsafe uses several
technologies to ensure the validity and status of the fieldbus communication, making it reliable to use with safety devices.
These measures include:
• Consecutive numbering.
• Watchdog time monitoring with acknowledgement.
• Codename per communication relationship.
• Cyclic redundancy check for data integrity.
Communication over the non-safe transmission systems is called the "black channel".
Danfoss A/S © 2022.02
STO demanded
Time
Debounce time
Time
t
N O T I C E
Safety Functions
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