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instruction to dissable plc if hmi is disconnected

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  • instruction to dissable plc if hmi is disconnected

    Currently if I disconnect my hmi from my plc the plc will continue to operate normally . What I want is some kind of NO contact I can put into my "control power" logic line that will open when I disconnect the hmi from the plc. I am communicating from hmi to plc via a single direct ethernet cable. seems like this should be easy... just not sure what to use.


  • #2
    What PLC and what HMI?
    Model numbers please.

    If a full CMore, you can use the Good Communication Toggle bit. It toggles on a 5-second interval.(in PLC<->Panel..Panel to PLC)
    You can watch this bit in the PLC and take whatever measures you need in the event of a disconnect.

    If it is a CMore Micro, try ZEROING the Current Screen tag value and watch for the panel to repopulate it. -- I HAVE NOT TRIED THIS and do not know how this may affect any existing code.
    Last edited by kewakl; 01-15-2020, 10:13 AM.


    • #3

      This tag is located in the HMI? If so I imagine I would need to export the tags from the HMI and imort them into the PLC, is that correct?


      • #4
        In the PAC, pick the boolean you want to use. Make note of its system ID. C-nnnnnnn
        In the HMI go to the Panel to PLC section. Locate the Good Communication Toggle. Make your tagname in the dialog. When you leave that field, the software will prompt you to define this tag. In the popup (Tag Database Editor) dialog, ensure the datatype is DISCRETE (it should default to this because of the field topic)
        Enter the target PLC --- your PAC device.
        Put a C in the Memory Type field and the number of the bit in the Address field.
        Acknowledge the changes.
        Dump the edited programs - in the PAC, watch the new tag for a 5-second toggle.


        • #5
          Ha, it worked! its these simple things that trip me up lol.

          Thank you!


          • #6
            Originally posted by Kp386 View Post
            Ha, it worked! its these simple things that trip me up lol.

            Thank you!
            Kewakl is one of the experts on use of the PxK.
            Why worry? If you've done the best you can, worrying won't make it any better

            - Walt Disney