Siemens SIMATIC ET 200AL, System Manual

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Functions
5.4 Media redundancy (ring topologies)
PROFINET with STEP 7
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Function Manual, 05/2021, A5E03444486-AL
Function of the interconnection ports
Interconnection ports are appropriately configured PROFINET ports of the 4 devices for MRP
interconnection. The primary or secondary connection of the rings exists between the
interconnection ports.
Via the interconnection ports; the MIM is always informed about the connection status
between the Primary MIC and the Primary Coupled MIC ("primary connection") as well as its
own connection to the Secondary Coupled MIC ("secondary connection").
Depending on the connection status of the interconnection ports, each MIC sends a message
to the MIM when its status changes (Link-Up or Link-Down).
In regular operation the data between the two rings is exchanged over the primary
connection (primary link) and the MIM blocks its interconnection port.
Link-Down of the primary connection
In the figure below, the primary connection was interrupted (Link-Down).
① Link-Down
② Status message: Link-Down primary connection
③ Blocking of the interconnection port is released
④ Data exchange via secondary connection
Figure 5-48 Link-Down of the primary connection
With a Link-Down of the primary connection ① , Primary MIC and Primary Coupled MIC send
the status message "Link-Down" via all lines ② .
The MIM then unblocks its interconnection port at ③ and informs the MRP managers in both
rings to trigger the reconfiguration of the rings.
After the reconfiguration, the data exchange between the two rings takes place via the
secondary connection ④ .
As soon as Primary MIC and Primary Coupled "Link-Up" for the primary connection, the
MIM blocks its interconnection port and informs the MRP managers in both rings to trigger
the reconfiguration of the rings.
After the reconfiguration, the data exchange is again carried out via the primary connection.