VIM2 Communication issue

Hi, I was hoping if anyone can help me out with VIM2 Communication issue we are facing. we are using DeltaV Version 15.

We recently re-built ProPlus Station (egnineering Workstation) due to trends issue.

After rebuilding, although everything is working fine, VIM2 controller is communicating with field PLC.  It can read all values but it cannot write to PLC.

Earlier it was working fine, it can both read and write to field PLC. It is using Modbus TCP/IP protocol.

There has been no change in PLC configuration, we suspect that something is wrong at DCS / VIM2 end.

Can anybody help out ?

• Control
• DeltaV #DCS
• configuration
• DeltaV

Abdul Samad

• 23 Jan 2026 6:06 AM
• Cancel

3 Replies

• Andre Dicaire

  

  • 23 Jan 2026 4:38 PM

  Hard to say, but could you clarify an example in detail. I would start by using an OUTPUT only data set (no readback) and view its data in diagnostics (Show dataset values). Are you able to write to this IO register successfully. Then look in the PLC to see if the value is reaching the PLC. If the value is making it to the controller's IO map, we know the issue is not related to the configuration of the module. This cannot be an OUTPUT with read back as the written value is immediately overwritten by the readback and if as you say, input direction is working but output is not, the readback would be receiving the unmodified value.
  
  Output with readback would be used when the value can be set by either the DCS or the PLC, depending on operating mode in the PLC. Think PID/OUT value in Auto or Man. Some PLC logic is needed to decide if the DCS value is master and held or if the PLC is master. The PLC can possibly overwrite the DCS value by design, and if this is happening, the Register value in DeltaV will track the value in the PLC.
  
  If you can confirm that the Output Dataset fails to see a change from the module via diagnostics, your issue has to be in DeltaV configuration/VIM configuration. Something has changed. If the Output only registers show written values, I would verify the receiving array register in the PLC. Can you change this value manually and it holds value? That tells me there is no value refresh happening in the PLC. But if the value is reset, then clearly the PLC is overwriting writes.
  
  If the data gets to the IO register as seen in DeltaV, issue is not in DeltaV. But if not, the DeltaV configuration needs to be evaluated/followed. Dataset configuration direction and any event messages in Event Chronicle need to be reviewed.
  
  If receiving register is being reset by PLC, evaluate the source of the overwrite. It could be a second Data set in DeltaV overwriting the first. Or there could be some condition in the PLC that has been set via logic that is now overwriting and this code has always been there. Yes, no change made in the PLC, but it might still be the PLC.
  
  If you can see the change in DeltaV diagnostics, and you can manually change the destination register and it holds, then we know the write is failing, that involves the VIM, the network and in some way the PLC's ability to receive writes. If you get to this point, a wireshark capture and evaluation of actual data packets would likely be useful to isolate further.
  
  Note that if you have all output datasets set to with readback, the DeltaV diagnostics will by showing you the polled readback values. You can still go the PLC destination register and change it manually, if that value holds, you would then see it in DeltaV diagnostics. But if it is overwritten, either the PLC is overwriting written values or the value is being written to by a second dataset or other ModbusTCP client.
  
  Wireshark is a free software tool and very useful for trouble shooting network traffic issues.

  Andre Dicaire

  • Cancel
• Abdul Samad

  

  • 29 Jan 2026 1:56 PM

  In reply to Andre Dicaire:

  Thanks for your detailed response.
  
  Our Datasets are configured with Readback enabled.
  
  We have unchecked Readback, re-downloaded and checked data sets however value are still not writing to respective registers.
  
  DeltaV Diagnostics shows "Output Transfer Failure"
  
  All configuration of Data Sets seems OK.

  • Cancel
• ApurvaPatel

  

  • 30 Jan 2026 5:51 AM

  It is definitely strange that the VIM was working fine before the Pro-Plus rebuild, but has stopped now. Based on my experience at other sites, here are a few things we can try:
  
  Reset the VIM: If the process is at a stage where we can, try decommissioning and recommissioning the VIM. This often clears up similar issues.
  
  Check the.VIO File: Double-check that any changes in the controller configuration have been mirrored in the.VIO file.
  
  Special Data: Take a look at the special data under the data set for any inconsistencies.
  
  Let me know if these steps help!

  • Cancel