Modbus Address

Modbus Address

This Address field in the App is in the Modbus Protocol format and the most commonly PLC 6-digit address scheme.  This address scheme provides the full 16 bit protocol address range ( 0 to 65535 registers) as defined in the Modbus Specification .  The 6 digit scheme combines the function code with full address rage as single long integer value.  The 6-digit address scheme uses “1-based” or offset compare to “0-based” Modbus frame that is sent over the wire.  For example, the table below shows PLC “6-digit” address and the Modbus Monitor App decodes function code and 5 digit Modbus register address (MMA = Modbus Monitor Advanced).  

6-Digit Address Scheme

  • 0x Read Coils: 000001 = >  (0 00001) => 1 = Function 1, Read 1st Coil
  • 1x Read Coils: 100001 = >  (1 00001) => Function 2, Read 1st Discrete Input
  • 3x Read Input Registers: 300001 => (3 00001) = Function 4, 1st Register
  • 4x Reading Holding Registers: 400001 => = (4 00001) = Function 3, 1st Register

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