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Retentive Memory or Initial Value Write with C-More EA9 to AB SLC500

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  • Retentive Memory or Initial Value Write with C-More EA9 to AB SLC500

    I am replacing an old PV550 with an C-More EA9. The PV550 had an Initial Value that the HMI would write to a register in the SLC500. I am trying to duplicate this action either with retentive memory, as the value really never changes or some sort of one time write to the PLC. I am supposing a could use Event Manager to do it, but by the time the HMI boots up the first scan bit on the processor has already changed states. Any thoughts.

  • #2
    What is this value that is written? There is a Good Com Bit in the HMI I use. There are times when I do not want the PLC to do "anything" except boot up until the HMI is booted and running. I use the Good Com Bit to then allow the program to "Run". Not sure this is something you could incorporate into your system.


    • #3
      These are just integer values or setpoints. Values that if ever set I do not wish to have them overwritten. I cannot change the AB program as the manufacturer of the machine has requested not to and so has my boss at the request of the manufacturer. I think I can do it using Event Manager. I basically wrote a first scan type Event.


      • #4
        That "feature" in the PV550 almost got a guy fired at a previous job. The PV550 had a loose power wire, and rebooted unbeknownst to the operator. It changed a setpoint using that initial value "feature" and altered the width of the stock being produced to a slightly narrower value, making it some very expensive scrap. He rolled up a couple dozen rolls of this stock, which was later rejected by a subsequent process in the factory and when he was called into the office to get wrote up, he was sure he had not changed the setting, had done the proper manual verifications as required by their SOP, so they got me involved. I found what was the real cause of the "PLC changing by itself" and promptly did away with that setting in the PV550, tightened the loose wires, and all was well.

        The moral of the story, is there is a good chance you don't need that initial value feature at all.