Profibus node dignosis

Hi Experts ,

I am using IM 151-8 CPU with DP master card and 2 atlas copco controller are connected with PLC via profibus ( Node 14 and node 15). How i can able to know node is disconnected ?

I am using FB126, db126 for profibus node dignosis . As per the manual i should get the bit status in word 1591 and 1592 for node 14 and 15 respectively .(as 1578 assigned for node 1). But in db126 i got the value zero(hex) which means it is not configured .

Kindly guide me the same .

Hello Satya Suravit,

what about sending a toggle bit to your atlas copco controllers and let them send back that toggle with a different bit (copy toggle to return bit)? You can then check in your cpu if ON- or OFF-state of return bit exceeds 50% of toggle cycle. If so, communication is broken.

regards

Hi ,

For this current scenario , i can't change in Atlas Copco Controller . I want some dignosis from my PLC end .

hi SATYA,

If a Profibus-node has a failure on the bus, you normally get an entry in the diagnostic buffer and the OB86 is called. In this OB you are able to check, why the OB is called and you also can react to failures that happen when a node is not on the bus. In the local data of OB 86 you can see what node is gone and coming back. 

Try to insert the OB 86 in your poject and look at the S7-help(mark OB86 and press F1). There is a good describtion about it. 

hope this helps,

regards,

Hi ,

My point is i want to display this bus failure on HMI . How i can show the dignostic buffer in HMI .

As described by mopS04, you can use OB86 to analyse the reason for the call of OB and for each case set a certain variable to an error number (where 0 is no error).

This number you can pass to the HMI and in the HMI you will call certain alarm texts (that you design), depending on value of that variable.

regards

SATYA SURAVIT

Hi ,

My point is i want to display this bus failure on HMI . How i can show the dignostic buffer in HMI .

 If you can see in your programm what going on, or what failure you have you can also give it to the HMI.

Just set a bit for bus failure on node xy in OB86 and monitor that bit in your HMI. This is the easiest solution. 

hope this helps,