MTownsend (Customer) asked a question.

April 1, 2026 at 6:20 AM
Which PLCs support Retentive Tag Sync, are USB drives supported?

Hi,

 

We're currently using a number of P2-550 PLCs and I occasionally have issues where the PLC dies with the dreaded E03901 error (tried all the fixes). I can recover the PLC (unload project, force firmware update, reload and clear) but this loses the retentive data.

 

The new RTS logic (PS 4.6.1.7) would be a game changer as I can recover, or swap the PLC and recover the tags.

 

I'm looking at 'upgrading' the PLC, from series 2 to series 3, but ideally I want to make use of the RTS feature. I've created a new project (for the P3-622) and added RTS to the ladder but the device needs to be defined in the Hardware Config>File Systems. However, only MicroSD is available, the help page is absent and, from what I can gather, the P3-622 does not have a MicroSD slot.

 

I appreciate this feature is only a day old but I would greatly appreciate some advice.

 

 

  • 6 answers
  • 131 views

  • ADC Community_02 (Automationdirect.com)

    Thank you for bringing this to our attention!

     

    We were able to confirm that even though the widget is labeled MicroSD, it will function correctly when using a USB drive in your hardware configuration. All file operations, including Retentive Tag Sync, work as expected.

     

    We have submitted a ticket to our development team to have the label corrected in a future update. We appreciate your patience!

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  • PouchesInc (Customer)

    E03901 is usually a programming error isnt it? In that the way you are asking the PLC to execute the logic ha timed out while waiting for a piece of data or connection.

  • ADC Community_02 (Automationdirect.com)

    Per help topic P205 E03901 is due to a watchdog timeout. Have you tried increasing you timeout or look into what logic maybe causing scan time to exceed the timeout?

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    • MTownsend (Customer)

      Yes, timeout at 1000ms and no loops in the project. I've replaced the base, CPU, PSU and the AC/DC power supply and the issue will always come back.

       

      The confusing part is that it can run for months without any issues and then the E03901 error appears. When it happens it will tend to repeat every few hours until I 'reset' the PLC or replace the PLC (we hold a spare with the latest project loaded).

       

      I was considering switching the master PLC from a P2-550 to the P3-622 (the RTS backup easily justifies the price). Do you think we'd see any benefit over the P2-550?

       

       

       

       

       

       

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      • ADC Community_02 (Automationdirect.com)

        All 622 Series CPUs support a comprehensive range of features, including:

        • File Operations (including RTS)
        • Modbus Device Operations
        • Secure Web Server
        • Custom Serial Instruction
        • MBUS Instruction
        • NETW Instruction
        • ASP Instruction

        These capabilities go beyond what is available in the 550 Series, making the 622 Series the ideal choice for more demanding applications.

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  • ADC Community_02 (Automationdirect.com)

    Thank you for bringing this to our attention!

     

    We were able to confirm that even though the widget is labeled MicroSD, it will function correctly when using a USB drive in your hardware configuration. All file operations, including Retentive Tag Sync, work as expected.

     

    We have submitted a ticket to our development team to have the label corrected in a future update. We appreciate your patience!

    Expand Post
    Selected as Best

  • MTownsend (Customer)

    Thank you for the advice. I have swapped over to the P3-622 and can confirm that RTS works flawlessly with a USB flash drive in the top most USB B socket. 😀

 

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