Discrepancy Tolerance; Safety Fieldbus; Profisafe - Danfoss VLT FC 280 Operating Manual

Operating Guide | VLT® Midi Drive FC 280
5 ms max. Test pulse
T37/38
STO request
state
STO valid
STO invalid
Figure 33: Debouncing

Discrepancy Tolerance

6.4.3
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
Figure 34: Discrepancy Time
The discrepancy time does not extend the response time of the safety function. The drive activates its safety function when the
earlier valid signal arrives.

Safety Fieldbus

6.5

PROFIsafe

6.5.1
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.
l
Watchdog time monitoring with acknowledgement.
l
Codename per communication relationship.
l
Cyclic redundancy check for data integrity.
l
Communication over the non-safe transmission systems is called the "black channel".
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STO demanded
Time
Debounce time
Time
t
NOTICE
Safety Functions
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