I had the same problem that I needed to read and write to the same variable from an HMI using ModbusTCP.
But unfortunately, it seems that this is not possible anymore in Codesys 3.5.
In my solution, i changed the driver to OPC UA, but this might nog be possible for you.
Jesper
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I have a Wago PLC and would like to connect with modbus TCP.
It is possible to create READ/WRITE variable?
Gianni
I use the function FC23 but i can't use the same variable in read and write
Gianni
Hi Poix.
I had the same problem that I needed to read and write to the same variable from an HMI using ModbusTCP.
But unfortunately, it seems that this is not possible anymore in Codesys 3.5.
In my solution, i changed the driver to OPC UA, but this might nog be possible for you.
Jesper
Thank's for your replay, but I have to connect to a Wago PLC.
Gianni
May be possible to use Network Variable instead of MB protocol. CoDeSys doesnt handle RW variables in MB registers any longer.