Applies To:
  • CitectSCADA 5.xx, 6.xx
  • CitectHMI 5.xx, 6.xx

The Schneider TWIDO PLC uses different addressing and always starts at 0 for Registers, Inputs, Outputs etc but the classic Modicon PLC using Modbus always starts at 1. This could cause problems and confusion when configuring the addresses in CitectSCADA.

In the Modbus the holding area are (4x) and in the Twido are %Mw. The Coil area in the Modbus are (0x) and in the Twido are %m. In other words if a Variable tag in CitectSCADA addresses 40001 to the Modbus driver then this will address the first Twido register i.e. %mw
One remark: Make sure that you shift the address because the Twido addressing always starts at 0 and Modbus always starts at 1, so the mapping will be as follows.

%mw0 -> 400001
%mw1 -> 400002
%m0 -> 000001

There is also a link to a site shown below that refers to the addressing of Twido inputs through Modbus:

The main extract from this site is as follows:

In Vijeo Designer select IEC61131 syntax for the Modbus equipment (Twido). You will then have access to %Mx or %MWx:Xx (memory bits, and Memory words (%MW).

It is not possible to look at %Q and %I directly you will have to use an operate block in the twido software to move the inputs into a memory word, you can then read 'each' individual bit of the %MW.

For example write an operate block containing '%MW100:=%I0.0:12' This will copy the values of input %i0.0 - %I0.11 into %MW100.

You can then create discrete variables starting %MW100:xo etc.


Schneider, TWIDO, Modbus, Modnet