Chapter
3
Operating Instructions
UE4155
20
© SICK AG • Industrial Safety Systems • Germany • All rights reserved
8010178/TF82/2010-03-05
Subject to change without notice
Product description
Monitoring the discrepancy time
The discrepancy time is the maximum period in the case of the two-channel selection,
within which both the inputs of the field-signal connection may have an inadmissible
status without the bus node detecting an error. Discrepancy time monitoring commences
when the status of an input changes. The bus node detects an error when both inputs of
the field-signal connection do not have the same or opposite statuses at the end of the
discrepancy time.
If you have set the discrepancy time to
Inactive
, the bus node does not generate an error
when the status of only one input changes.
If an error occurs …
the bus node transfers failsafe values to the PROFIsafe telegram. This value is 0 for
both inputs.
the bus node sets the
discrepancy-time overrun
diagnosis bit of the field-signal
connection.
Tab. 5 clarifies the connection.
Input signal
Process image
Two-channel selection
In A
In B
Status
In A
In B
Discrepancy-
time overrun
diagnosis bit
0
0
Inactive
0
0
0
0
1
Discrepant
0
0
1
1
0
Discrepant
0
0
1
Equivalent
1
1
Active
1
0
0
0
0
Discrepant
0
0
1
0
1
Inactive
0
0
0
1
0
Active
1
0
0
Complementary
1
1
Discrepant
0
0
1
For the duration of the set discrepancy time, the bus node does not transfer any other
signal changes of the field-signal connection to the PROFIsafe telegram, nor does it
route this to other connections.
When the input status changes from
Inactive
to
Active
, the discrepancy time delays the
change in the process image.
In order to delete a discrepancy-time error, you must reset both inputs to their
Inactive
status.
Tab. 5: Input signals and
process image at the end of
the discrepancy time
Notes