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CHAPTER 15 TROUBLESHOOTING
15
15.3 Checking for Functional Errors
15.3.4 Ethernet communication
(5) Communication is slow or unstable
If communication is slow or unstable, check the following items.
Check item Corrective action
IP addresses are duplicate.
Correct the duplicate IP address. The duplicate IP addresses
are checked in the following way.
• Detect the IP address using the Find CPU function.
• Remove the connected device from the network, and
perform PING with the IP address of the removed device.
If any device responds, IP addresses are duplicate.
The number of connections of UDP exceeds the number set
to "UDP" of the open setting (each number of connections of
MELSOFT connection and the MC protocol).
Keep the number of connections of UDP within the number
of the open setting.
Communication is based on UDP. Perform communication on TCP.
Communication is not retried.
Retry communication.
Increase the number of retries.
The hub, router, or cable has an error. Replace the hub, router, or cable.
Communication of devices other than the CPU module is not
stable.
• Take noise reduction measures.
• Check the amount of network traffic. If the traffic causes
instability, reduce the amount of traffic.
Many of unnecessary broadcast data are received.
(The broadcast data volume can be checked in "Connection
Status" in Ethernet diagnostics)
To reduce the Ethernet communication load of the CPU
module, increase the service processing time in the service
processing setting of the PC parameter.
Reduce the broadcast data volume on the network.
• Identify a broadcasting device, and restrict the broadcast
data volume. (Devices such as personal computers or
routers.)
• Use filtering of broadcast data with a router to prevent the
CPU module from receiving them.
• Separate the network with frequent broadcasts from the
network of the CPU module.
The Ethernet communication load of the CPU module is
high.
• Increase the service processing time in the service
processing setting of the PLC parameter.
• Reduce the number of connected devices.
• Reduce the communication frequency per connection and
data volume.
The interrupt program is used.
Reduce the frequency and process time of the interrupt
program.
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