Communication
11.2 PROFINET
S7-1200 Programmable controller
System Manual, V4.2, 09/2016, A5E02486680-AK
817
Condition in which PROFINET network might stop
When changing the IP address of a CPU online or from the user program, it is possible to
create a condition in which the PROFINET network might stop.
If the IP address of a CPU is changed to an IP address outside the subnet, the PROFINET
network will lose communication, and all data exchange will stop. User equipment may be
configured to keep running under these conditions. Loss of PROFINET communication may
result in unexpected machine or process operations, causing death, severe personal injury,
or property damage if proper precautions are not taken.
If an IP address must be changed manually, ensure that the new IP address lies within the
subnet.
Configuring the PROFINET port
By default, the CPU configures port(s) of the PROFINET interface for autonegotiation. For
autonegotiation to function properly, you must configure both stations to autonegotiate. If one
station has a fixed configuration (for example, full-duplex at 100 Mbps) and the other station
is set to autonegotiate, then autonegotiation fails, resulting in half-duplex operation.
To overcome this limitation of autonegotiation, the S7-1200 provides an option to disable
autonegotiation. When you disable autonegotiation, the S7-1200 is automatically configured
for full-duplex operation at 100 Mbps.
You can set the transmission rate and duplex to a fixed value for each port:
1. Select Advanced options and the port you need to configure. Then, select Port options.
2. In the Connection, Transmission rate / duplex field, select one of the following:
– Automatic: The CPU and the peer device determine the port’s transmission rate and
duplex by autonegotiation.
– TP 100 Mbps full-duplex: If you disable autonegotiation, the port operates at 100 Mbps
full-duplex. If you enable autonegotiation, the port can operate at 100 Mbps full-duplex
or another transmission rate / duplex that is autonegotiated between the CPU and the
peer device (which places a message in the diagnostic buffer if "Monitor" is selected
(see below)).
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