Problems with Modbus Serial on Micro820 controller

[MathiasPM]

Hello plctalk,

I am in the proces of integrating a Micro820 with the purpose of getting data out of 4 AB Powerflex 4M drives through Modbus Serial.

In the workshop the PLC works and is getting data out. At first glance, then i install the PLC at the site, it is also working and seems fine for a couple of hours. Afterwards, at some point, the communication stops working, and throwing out the errorcode 55 from the Msg_Modbus FB.

I am using the exact same modbus paramters in both the controller and the drives (19200 baud-rate, 8E1 and so on). The drives has the node addresses 2,4,6,8.

I cant seem to wrap my head around it. Could it be, that the serial port has shorted? Or are there anyone else who has encountered problems alike?

I would be happy if someone had anything to say about it.

TIA.

 

[MathiasPM]

Found the problem.

As the Micro820 was in another enclousere than the drives, and the two enclosures was not properly equalized (do not know if it is the right word?), the embedded serial port had shorted.

I now installed a 2080-SERIALISOL and hopes it will be the problem solver.