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Modbus functions
Function no.
Description
Meaning
1 (0x01)
Read Coils
Read states of 1 to 8 bits according to bit list
3 (0x03)
Read Holding Registers
Read several consecutive registers
4 (0x04)
Read Input Registers
Read several consecutive registers
5 (0x05)
Write Single Coil
Write state of a single bit
6 (0x06)
Write Single Register
Write single register
Exception codes
Codes
Description
Meaning
1
Illegal Function Code
Unknown function or subfunction code
2
Illegal Data Address
Invalid register address
3
Illegal Data Value
Inconsistent coding for number of registers/bytes, data value
Exception codes (error codes) are returned in case of invalid function or register access.
Interface information
Modbus interface
Expansion module EM-IP
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