Devicenet

Hie Everyone

I am not a controls engineer nor plc programmer i want to learn and i am trying very hard. At my work place its mostly Allen Bradely (5K and 500) then Mitsubishi running Medoc.One day i was in front of a computer running RSView, Alams button flashed red , click on it, showed a green screen with a list of faults to some panel view 600 on devicenet saying there are faulty. Looked at one pv6oo indicated comms error. Went to the plc on the devicenet scanner card there was bus disconnected checked the 24v dc was alright. Cyled power to the plc. This time indicated NoTx which i found out that it means no trasmission. Checked for continuity of the blue and white cables ok. I am stuck now is it something along the cables or the scanner module?
thanx in advance.

Hi

Did you check to see if your plc is in run mode as no tx often means the run bit needed in the plc code is not high.(Maybe plc faulted)

It would be un common to lose all devices on the network unless

you lose your 24 volt which you have checked.

Let me know how you got on

Donnchadh

In my experience, a bus off condition (fault 91 on the scanner card) means that you definitely have a cabling problem. The only way to recover is to fix the problem and cycle network power. I have seen a loose resistor, a bad solder on an AB powertap, and a stray wire whisker all cause this problem. Devicenet needs to be terminated at both ends with 120 ohm resistors, so across the blue and white wires you should read 55-65 ohms. I'd take the time to walk the whole network and verify that the network is properly terminated and that all connections are neat and tight.
Let me know what you found; sorry for the late reply.

Thanx Donn and WW there was short in one of the spliter boxes and i relaced the box everything went well after that.