Right now I'm developing an application with a V350 and a HMI FUJI ELECTRIC HAKKO MONITOUCH V815 .
The V815 of Fuji is a 15" screen and it connect with Unitronics with PCOM protocol serial or ethernet. If I use the driver Unitronics or UnitronicsTCP I can read and write directly MI, MB, ML, DW,... all but X operands.
Before I used Modbus TCP, but now it is easier.