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Ever see Modbus address like this?

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  • Ever see Modbus address like this?

    From a Generac generator, these are the registers

    0038:fffe 0034:ff3e


  • #2
    That doesnít look like a modbus address, which is just a number. That looks like two memory banks, each referenced by address and measured in length. Which one is the address and which one is the block length, I canít tell.

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    • #3
      I think its hex. Does DL do hex registers?

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      • #4
        Is this in the documentation - or is this from a raw packet sniffer?
        There are 10 kinds of people in this world, those who know binary, and those who do not.

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        • #5
          Originally posted by franji1 View Post
          Is this in the documentation - or is this from a raw packet sniffer?
          I think its from a packet sniffer.
          Here is the project https://github.com/jgyates/genmon/wiki
          Say reg 0009, should be 49 in domore right? or 400009?

          Thanks

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          • #6
            Originally posted by trimixdiver1 View Post

            I think its from a packet sniffer.
            Here is the project https://github.com/jgyates/genmon/wiki
            Say reg 0009, should be 49 in domore right? or 400009?

            Thanks
            Actually, you have to add 1. The Application Layer uses addresses like 40001 (starting at 1). But at the packet level, the offset is 0-based, along with the removal of the Holding Register Type value (i.e. remove the leading 4). So 40001 will have a Holding Register packet address of 0x0000. Hence, a Holding Register packet address of 0x0009 (assuming raw Modus/RTU or /TCP hex, NOT ASCII) is 40010.

            There are 10 kinds of people in this world, those who know binary, and those who do not.

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            • #7
              Originally posted by franji1 View Post

              Actually, you have to add 1. The Application Layer uses addresses like 40001 (starting at 1). But at the packet level, the offset is 0-based, along with the removal of the Holding Register Type value (i.e. remove the leading 4). So 40001 will have a Holding Register packet address of 0x0000. Hence, a Holding Register packet address of 0x0009 (assuming raw Modus/RTU or /TCP hex, NOT ASCII) is 40010.
              Yes, forgot....

              So 0009 is 10.

              Hope it all works like they say

              Thanks!

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