Mitsubishi MELSEC-F User Manual page 266

11 TROUBLESHOOTING
11 - 41
POINT
If the external device communicates normally, the following conditions occur.
For TCP communication
When the external device's open status is complete, LEDs C1-C8, which are in
correspondence with connections 1-8, turn on.
For UDP communication
When external device communication is possible, LEDs C1-C8, which are in
correspondence with connections 1-8 turn on.
MELSEC-F
11 - 41