PROFINET/Ethernet
5.3 Timing and runtimes
Power Line Booster
Operating Instructions, 11/2019, A5E36203125A-AG
73
5.3.3
Configuration of the monitoring time
Due to the following effects, the average PLB cycle time calculated in the section
Configuration of the PN update time (Page 72) is regularly exceeded:
1.
Registration of PLB slaves in a segment.
Sounding of the carrier frequencies of the master and slave modem occurring during
registration results in a media assignment that makes the media unavailable for the cycle.
2.
Deregistration of PLB slaves from a segment.
As soon as a slave can no longer be reached, you experience interruptions in the PLB
cycle due to timeout periods (see section "Traffic Manager time configuration (Page 95)").
3.
Impedance change due to plant elements such as switches and trailing cables. The
sounding of carrier frequencies can also result in a longer cycle in this case.
4.
Interference on the medium, e.g. caused by EMC or short-term deterioration of the
contact quality of the sliders.
5.
Cyclic sounding of carrier frequencies to optimize the connection.
6.
Crosstalk of the powerline signals (Page 116) from other plants or plant units. (This effect
must be prevented by suitable insulation and attenuation during installation of the plant).
To determine the PN watchdog time, you must expect a significantly longer PLB cycle time in
total for a segment with 40 vehicles. The current cycle time of the PLB master can be read
via the web interface in the Cycle times (Page 104) table. In addition to this latency,
additional effects (e.g. response time of PLC and field devices, processing times as well as
upstream and downstream cycles, such as the PN cycle) must be taken into consideration.
Below you can find a calculation of the maximum system latency using PROFINET as an
example.
It is based on a maximum PLB cycle time of 400 ms which is within the expected range for
applications with 40 PLB slaves per segment.
Содержание SIMATIC Power Line Booster
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