Emerson Exchange 365

VIM2 Inputs Transfer Error and Outputs Transfer Error

We had an incident last week where the communication to all the devices on the VIM2 with Modbus TCP protocol alarmed loss of communication on the DCS.  Looking in the Event History, I see lots of times where a group of tags being read from the same device on the VIM2 card show “Inputs Transfer Error” or “Output Transfer Error”.  Usually six items get entered into the event history at the same time, and the State of one of them is “Event Limited”.  But I see these errors fairly consistently, and we only had one instance where it triggered alarms on the operator station.

 

I can’t find anything for an alarm state “Event Limited” in BOL.  Does that mean a lot more entries would be in the history but there were too many at once to log?

 

I can’t find anything to help determine what causes chronic “Inputs Transfer Error” or “Outputs Transfer Error” other than references to standard I/O.  Is this a configuration problem or a wiring problem?

 

I don’t understand why we had the one instance of loss of communication from the devices on the VIM2, yet there is a chronic issue of the transfer error alarms.  I don’t see anything else in the event history.

 

According to Diagnostics, there are no issues with the devices on the VIM2.

 

Thanks,

Maureen Radi

Control/Process - Tuscola

 

Equistar Chemicals

625 East U.S. Highway 36

Tuscola, IL  61953

Office: +1 217.253.1270

Mobile: +1 217-369-3536

 

Maureen.Radi@lyondellbasell.com

www.lyondellbasell.com

 

 

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meradi

• 18 Jun 2018 7:04 PM
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1 Reply

• Matt Forbis

  

  • 29 Jun 2018 6:54 PM

  I probably won't have all the answers, but let me give you a few things you might look at. First, usually Event Limited is an error message that comes in when the node is sending so many events to the Pro+ at once that it cannot keep up. When the buffer runs out of space, it just sends an event limited.
  
  So the real question we need to solve is why there are many input and output transfer errors. An input an output transfer error is usually saying that a read or write cannot happen. A common occurence of an output write error that's easy to understand would be if you had a wire to an output parameter as well as a calc or action block writing to the same parameter. That would give you an output transfer error because the two writes are conflicting. Another example might be trying to write a negative number to an unsigned integer parameter.
  
  So, that being said, if you are seeing chronic input and output transfer errors, there is a possibility of a configuration issue somewhere. I would start by checking to make sure there are no conflicting writes, all your datatypes are appropriate all the way through the chain of logic and other items to see if you can find a place where there might be a problem writing a value. The thing with Input and Output transfer errors is that your logic might appear to work correctly, but it's really not.
  
  All that being said, I don't necessarily think your single loss of communication issue is necessarily related to the transfer errors (though it could be). More likely you have two separate root causes.

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