Communication
11.2 PROFINET
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
957
The following rules apply to a ring topology with media redundancy using MRP:
● All devices in the ring belong to the same redundancy domain.
● One device in the ring has the role of a MRP manager.
● All other devices in the ring are MRP clients.
You can connect non MRP-compliant devices to the network through ports not configured as
ring ports. You can only do this with devices that have more than two ports (for example, a
SCALANCE X switch or a PC with a CP1616).
You can have the following communication possibilities:
● MRP and RT: RT operation is possible with the use of MRP.
Note
The RT communication is disrupted (station failure) if the reconfiguration time of the ring
is greater
than the selected watchdog time of the IO device. You must select a watchdog
time greater than 200 ms for your IO devices. Refer to the "Watchdog time" section below
for further information.
● MRP and TCP/IP (TSEND, HTTP, ...): The TCP/IP communication with MRP is possible
because lost data packages are resent, if applicable.
● MRP and prioritized startup:
– If you configure MRP in a ring, you cannot use the "prioritized startup" function in
PROFINET applications on the devices involved.
– If you want to use the "prioritized startup" function, then you must disable MRP in the
configuration (the device cannot be part of the ring).
● MRP on PROFINET devices with more than two ports: If you operate a PROFINET
device with more than two ports in a ring, you should set a sync boundary on the ports
that are not in the ring. By setting the sync boundary, you define a boundary for a sync
domain. You cannot forward sync frames transmitted to synchronize devices within a
sync domain.
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