« previous next »
Pages: [1]

Author Topic: Maximum PLC ID for Modbus RTU  (Read 6192 times)

ccdubs

  • Full Member
  • Posts: 116
    • View Profile
Maximum PLC ID for Modbus RTU
« on: August 01, 2014, 04:42:34 PM »
I remember reading before that the PLC ID's were only valid up to a limit when using MODBUS RTU. I can't find this reference anymore, could you please confirm what this?

Thanks
Logged

support

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3170
    • View Profile
    • Internet Programmable PLCs
Re:Maximum PLC ID for Modbus RTU
« Reply #1 on: August 01, 2014, 11:57:49 PM »
According to Modbus specifications the ID for a Modbus slave may only be between 1 and 247.
Logged
Email: support@triplc.com
Tel: 1-877-TRI-PLCS

EDGAR

  • Jr. Member
  • Posts: 60
  • Automating concepts around the world!
    • View Profile
    • Kinemics
Re:Maximum PLC ID for Modbus RTU
« Reply #2 on: August 02, 2014, 08:00:25 AM »
Hi, and agreed!

You might be able to handle that many devices. However, if you are using RS-485 network,  the RS-485 transceivers may not be capable of driving that many devices in the same network. See http://www.modbus.org/ also see http://en.wikipedia.org/wiki/RS-485 for bias network termination and other details.

Ed
Logged
Low cost Modbus OPC DA Server, supporting Modbus RTU, ASCII, and TCP. Download your demo today! Go to www.kinemics.com/modbus.
Pages: [1]
« previous next »