GX Works "An unusable port ..." PLC Ethernet error

[Transistor 3]

CPU: FX5U Software: GX Works3 I've been programming this unit a couple of weeks. All of a sudden I've lost comms. The "Specify Connection Destination Connection" dialog looks OK (IP address is as before) but Connection Test reports An unusable port or IP address was specified, or the number of settable connections for MELSOFT exceeded its maximum. Please execute again after checking the following settings. - Port/IP address setting - Setting number for MELSOFT connections in open setting of target module - IP address duplication on network. All looks OK and I didn't change any settings. How do I re-initialise the PLC to reset the Ethernet port? (There is no serial port on the FX5U.) Many thanks.

[Gambit 326]

Does the Find button find the FX5U on the network? Have you tried the direct connection. The IP addressing is not needed when you use this connection.

[JanHrust 7]

You should to be able to connect to it and change settings if you plug a network cable straight from the PC into the PLC. In the Connection settings specify Ethernet selection, not connection via hub. That should do the trick.

[Theo V 17]

Hi Transistor, Keep in mind that your laptop network port must be in the same range as the PLC IP number. Best regards, Theo V.

[Transistor 3]

Thank you Gambit and JanHrust. I had forgotten to try direct connection. The only way I could get back to normal hub connection (so I can connect the HMI) was to delete the specified IP and let it default. (I was using the default 192.168.3.250 / 255.255.255.0 / 192.168.3.1.) I lost a couple of hours trying to do this. This gets me going for now but I'll need to change it before installation. Many thanks.

[Transistor 3]

Thanks, Theo. We cross-posted. Subnet: 192.168.3.0 Subnet mask: 255.255.255.0 Gateway (router): 192.168.3.1 PLC: 192.168.3.250 HMI: 192.168.3.8 Laptop: 192.168.3 Having got communications going again I had to specify the IP on the PLC again before the HMI would work. It seemed to accept the IP address this time. Thanks.