I am trying to interface sele EM2M, I am using Arduino Mega with RS 485 module. I want to read the internal registers I am using ModbusMaster library. The data which I want to receive is in the internal registers but I am not getting how can I read Internal registers. When I use other software to read data I am getting the out enter image description here

I also wanted to know the difference between Internal Registers and Holding Registers

Another questions how are the frames formed for communication in rs485 from the above image I can understand 01 04 but from where do they get 00 1A please explain the same.

  • I can't open the datasheet.
    – Juraj
    Commented Oct 16, 2020 at 19:39
  • Ahh I am also having problems with the same sorry I will ask the manufacturer and then upload the datasheet
    – Maaz Sk
    Commented Oct 17, 2020 at 4:28
  • @Juraj now you can download the datasheet
    – Maaz Sk
    Commented Oct 17, 2020 at 5:18
  • it is an image, but looking at it I didn't see "internal registers"
    – Juraj
    Commented Oct 17, 2020 at 9:30
  • gofile.io/d/qeQd1B link for datasheet I have added the same on selec EM2M Yes internal registers are not present I forgot where I saw internal register but I guess internal and Input registers are one and the same
    – Maaz Sk
    Commented Oct 17, 2020 at 10:00

2 Answers 2


The RS485 has no internal registers, all of that is in your target unit. Hopefully the instructions for that will tell you how to do it. Start by getting simple communications working then slowly progress from there.


The issue is been resolved. I was reading the holding registers and also I tried to read the Input registers but I didn't received any output it was because the register address entered by me was wrong when I referred to a Simply Modbus Master software from where I was able to receive the data when I send a command, from the same software I came to know about the frame structure and how they were formed. So when I tried to enter those register address they were working fine.

Thank you everyone for your help

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