Could we change CI854/CI840 profibus parameters live?
We are actually running 800xA 5.0SP2 Rev. C in a plant. We just commissioned a new AC800M and configured profibus communication. On this profibus link, there are few CI840-S800 I/O drops and a profibus slave to profibus slave gateway to exchange values with another DCS.
It looks like we get wrong values few times per hour for a very short period of time (less than 50ms). We are not sure yet where is the problem. But, we would like to try slowing down profibus communication to see if this could fix this issue.
We of course want to avoid to stop the plant process to make those tests. So, my question is: could we change CI854 profibus master settings without shuttting down the process? Could we do this live?
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Yes, it * should * work. However, it wont really solve your problem. If the bus works normally, the cable length and number of nodes is within spec and you're only loosing a small amount of data occasionally then the problem most likely will still happen at slower speeds. The physical installation of the bus and electrical interference are your most likely problems.
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And look at what is actually happening on the bus. It can diagnose issues with cable lengths, corrupt messages, timeouts etc. and should help pinpoint the problem.
Yes you can change some parameters of CI854 online for example Watchdog time, Slot Time etc. Baudrate can not be changed online. Idea is to change one parameter at a time and no too large delta.
When you say wrong values do you mean profibus communication drops few times per hour or you just get random values but communication remain healthy?
If later is the case then its not profibus issue. You need to check your transmitter.
CI840 does not have any relevant parameter to be changed online.
As Rob suggested, we ran Profitrace analysis this morning on AC800M side. We will do the other DCS side later.
Attached pdf show report and health summary. The gateway we are actually more concerned about is slave 77. Its square wave is not as nice as other slave, but do you think it's enough to cause issues.
Profitrace gives a "warning" because CI854 send sync commands to all undefined and not used addresses. It might be normal for CI854.
What do you think?