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RS_93224053-Newcomer
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December 12, 2025
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Allen Bradley DF1 Comms

  • December 12, 2025
  • 1 reply
  • 116 views

I have a Prosoft PLX51-DF1-ENI card connected to a PLC5 via  a DF1 serial cable. I need to get a Factorytalk SCADA and Kepware to communicate to the PLC. Kepware is required to allow comms to an old historian. When Kepware is disabled the Factroytalk SCADA can communicate to the PLC OK. But once Kepware is enabled the Factorytalk comms start to fail.. In Kepware I am using the Allen Bradley Ethernet Driver and the tags show good values. I have the tag scan rates set to 1000ms. It seems like to Kepware connection is overloading the DF1 comms. Is there anything I can try to get this to work

 

Best answer by pshashipreetham

Hi

 

This is a classic DF1 bottleneck scenario. Short, practical fix path below.

 

Step 1: Stop double polling the PLC
FactoryTalk and Kepware both poll the same DF1 path via the Prosoft module. DF1 is strictly serial and single-threaded. Concurrent masters will collide. Only one system should poll DF1 directly.

 

Step 2: Make Kepware the single master
Configure Kepware as the PLC's sole DF1 master. Expose data to FactoryTalk via OPC from Kepware. Do not allow FactoryTalk to talk DF1 directly once Kepware is enabled.

 

Step 3: Throttle Kepware aggressively
DF1 cannot handle fast scans.

  • Increase Kepware scan rate to 2000–5000 ms

  • Reduce Maximum Bytes per Request

  • Disable unsolicited reads

  • Group tags into blocks instead of individual addresses

Step 4: Limit concurrent connections
In the Kepware Allen Bradley Ethernet driver settings, reduce simultaneous requests. The Prosoft DF1 bridge does not queue traffic effectively.

Step 5: Validate Prosoft DF1 limits
Check PLX51-DF1-ENI configuration:

  • Confirm single connection mode

  • Verify DF1 baud rate and retry counts

  • Increase response timeout

Bottom line
Nothing is broken. DF1 is saturated. One master only, slower scan rates, Kepware as the broker. This architecture is the only stable way to run Kepware plus FactoryTalk on DF1.

 

Thanks,

1 reply

P
18-Opal
pshashipreetham18-OpalAnswer
18-Opal
December 23, 2025

Hi

 

This is a classic DF1 bottleneck scenario. Short, practical fix path below.

 

Step 1: Stop double polling the PLC
FactoryTalk and Kepware both poll the same DF1 path via the Prosoft module. DF1 is strictly serial and single-threaded. Concurrent masters will collide. Only one system should poll DF1 directly.

 

Step 2: Make Kepware the single master
Configure Kepware as the PLC's sole DF1 master. Expose data to FactoryTalk via OPC from Kepware. Do not allow FactoryTalk to talk DF1 directly once Kepware is enabled.

 

Step 3: Throttle Kepware aggressively
DF1 cannot handle fast scans.

  • Increase Kepware scan rate to 2000–5000 ms

  • Reduce Maximum Bytes per Request

  • Disable unsolicited reads

  • Group tags into blocks instead of individual addresses

Step 4: Limit concurrent connections
In the Kepware Allen Bradley Ethernet driver settings, reduce simultaneous requests. The Prosoft DF1 bridge does not queue traffic effectively.

Step 5: Validate Prosoft DF1 limits
Check PLX51-DF1-ENI configuration:

  • Confirm single connection mode

  • Verify DF1 baud rate and retry counts

  • Increase response timeout

Bottom line
Nothing is broken. DF1 is saturated. One master only, slower scan rates, Kepware as the broker. This architecture is the only stable way to run Kepware plus FactoryTalk on DF1.

 

Thanks,

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