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ModBus only write register - datapoint


  • My customer has device with holding register with "WriteOnly" flag. I can write value into this register, but reading from this register cannot be applied - "Illegal address error".

    I wish small checkbox for "exclude" datapoint from periodically reading process.

    Sorry for my English.


  • Oja,
    I've the same problem with a genset controller, and i've found a walk around:

    • Create a new data source for your modbus slave with just one point (the write only register) and without slave monitor points.
    • Disable point read exception alarms
    • Use an update period of 9999999 hours (it'll bother just at first update, never alarm again 'cause next update will be at 10 years ;))

    You need to create a new data source because you need to receive point read exception alarms from all the other read and read/write points on your modbus slave.

    Best regards,

    David Parra

    Attachment: download link


  • Yes, I already use this workaround, but I wish .... :lol:


  • This has been added to Mango M2M2, currently in alpha.


  • Thank you M2MSanta :)