Description of the RFC 4072S
108580_en_02 PHOENIX CONTACT 37 / 272
The F_WD_Time OUT for available and robust system behavior with the specified
PROFINET settings results as follows for the example configuration from the bus head (bus
coupler AXL F BK PN) and the Axioline F output module (AXL F PSDO8/3 1F). The values
listed and calculated above must be used in the following equation based on [4].
From this example it is clear that the bus cycle and transfer times, and in particular here the
PROFINET update time as well as the monitor time, are the values that determine the min-
imum achievable F_WD_Time. In particular, the monitor factor (multiplier of the update time
for aborting the connection if no data is exchanged) acts as the cut-off between availabil-
ity/robustness and the minimum achievable SFRT in the overall system.
If the PROFINET update time is maintained at 1 ms via “Reduction ratio (= 1)” and the mon-
itor factor is maintained at 3, the minimum achievable F_WD_Time OUT in the example is
calculated as follows:
The minimum F_WD_Time OUT is calculated as follows for the example configuration:
F_WD_Time OUT
min
= DAT + 2 x external bus runtime + 3 x T
ZSPNS
F_WD_Time OUT
min
= 1.5ms+2x25ms+3x5ms
F_WD_Time OUT
min
= 66.5 ms
T
Bus
=T
ZPNIO
+1xT
DAXLFBKPN
+2xT
ZAXLLB
T
Bus
=3ms+1x1ms+2x0ms
T
Bus
=4ms
F_WD_Time OUT
min
=1.5ms+2x4ms+3x5ms
F_WD_Time OUT
min
=24.5ms
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