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What are the function codes of the Modbus protocol used by IO Scanning in TCP-IP?

The following Modbus protocol function codes are used by IO Scanning on Ethernet TCP-IP:
  •  Read only = function code 03
  • Write only = function code 16
  • Read/write = function code 23
    • Note: It is no longer necessary to enter two lines for devices that do not support code 23. The module starts by transmitting its frame in code 23. If the device does not support this, it will use codes 03 and 16.
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