I am using a modbus compatible device (arduino board) on tcp/ip network. It works perfectly and I can read a remote register (HR) from Logo in a continuous way.

The problem is: My remote register in a 16 bit counter that I display on the LOGO display. I can see the counter value increasing as it happens, but if I disconnect network cable on remote device, the counter display on LOGO freezes and I cannot detect any error (connection lost, timeout, ecc.). On other words, I don't know if the counter is really stopping or the connection is broken.

Of course this is very bad. I cannot supervise a process if cannot know if the variable I'm reading is still alive.

Is there anyway in LOGO diagram to check/detect connection problems with a remote modbus device?

Yes, but it is not needed to set an output to arduino to have it back from it. I just coded the arduino board to toggle an HR continuously. So the Logo just has to monitor that this HR it is toggling...