Dear Olaf,
I used this one in the past and it worked good. HMS-Anybus
On the Scada-side its a Profibus and on the Unitronics-side its a Modbus Master.
So you only have to use the functionblocks for Modbus.
They have also a example for the V120 so it should be no problem to use it with the V280.
Best Regards
Thomas