Applies To:
  • CitectSCADA 5.xx, 6.xx, 7.xx 
  • VijeoCitect 5.xx, 6.xx, 7.xx

When using Modbus20/Modnet20 or Modbus30/Modnet30, the protocols allow you to use the %M and %MW of Unity addressing. However, it does not allow you to use the %I and %Q addressing of the input and output register, respectively.

How can we configure the variable tag defined in Citect to refer to those registers?

Modbus flat addressing is not supported by the Unity topological addressing. Therefore, in order to incorporate those registers in Citect, we will need to map the I/O to the internal storage in the PLC.

Therefore, the registers which have the addressing of %Ix.x.x.x or %Qx.x.x.x need to be mapped to %Mxxxx and/or %MWxxxx.

Then, we can use either %M or %MW addressing or the modbus equivalent format.

 modbus, modnet, unity, address, conversion, input register, output register, %I, %Q