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Software & Driver


Modbus Map


Modbus - Modbus Map [referenceable]

We distribute a constants file called ljm_constants.json that defines all information about the Modbus register map.  The dynamic filter & search tool below pulls data from that JSON file.

  • Name:  A string name that can be used with the LJM library to access each register.
  • Address:  The starting address of each register.  Valid through LJM or with direct Modbus.
  • Details:  Click to get text pulled from the description field in the JSON.
  • Type:  Specifies the datatype, which also tells you how many registers each value uses.
  • Access:  Read-only, write-only, or read & write.
  • Tags:  Used to associate registers with particular functionality.  Useful for filtering.

For a U3, U6 and UE9, see the deprecated Modbus system called UD Modbus.

Data Type Constants

TypeInteger Value

Other Versions

The ljm_constants Bitbucket repository contains some up-to-date text versions of the Modbus register map: