5-22
Communications Processor CP 541
EWA 4NEB 812 6188-02
5.3.6
Example of Verification of Safety Times
The example previously described (see Section 5.3.5) serves for verifying the
safety times.
We will now determine the safety time for a connection between the two pro-
grammable controllers, Stations 1 and 2.
By agreement with the inspector, a SINEC L1 safety time for receiving of 2 s
is specified.
You have determined the local cycle times from the example. They are as
follows:
Local Cycle Time for
STN 1
STN 2
STN 3
Sending (t
LUS
)
308 ms
164 ms
296 ms
2
sending (2
t
LUS
)
616 ms
328 ms
592 ms
Receiving (t
LUE
)
308 ms
304 ms
152 ms
2
receiving (2
t
LUE
)
616 ms
608 ms
304 ms
From these data and taking into account the formula in Section 5.3.3 and the
data in 5.3.4, we obtain the safety times as follows:
STN
Calculation
Value to be Set
1
(S5-115F)
First formula from Page 5-14:
SINEC L1 safety time for receiving >=
2
t
LUS,STN2
+ 2
t
LUE,STN1
+ t
L2
=
2
164 ms + 2
308 ms + 100 ms = 1044 ms
2000 ms >= 1044 ms
Condition is fulfilled.
Second formula from Page 5-14:
2000 ms – t
LUE,STN1
=
2000 ms – 308 ms = 1692 ms
Safety time to be set with COM 115 F =
1690 ms
2
(S5-95F)
First formula from Page 5-14:
SINEC L1 safety time for receiving >=
2
t
LUS,STN1
+ 2
t
LUE,STN2
+ t
L2
=
2
308 ms + 2
304 ms + 100 ms = 1324 ms
2000 ms >= 1324 ms
Condition is fulfilled.
Second formula from Page 5-14:
2000 ms – t
LUE,STN2
=
2000 ms – 304 ms = 1696 ms
Safety time for receiving to be set with
COM 95F = 1600 ms
Safety time for sending =
2
t
LUS,STN2
= 2
164 ms = 328 ms
Safety time for sending to be set with
COM 95F = 400 ms
Example
Local Cycle Time
Safety Time
CP 541 with S5-95F/S5-115F