Hello,

then also standard protocols like Modbus RTU and Modbus TCP are available. You need only take to account that HMI work as Master/Client and your PLC as Slave/Server. Important question is what exactly HMI type you have because not all HMIs have Modbus protocol available.

Update: maybe also Profibus can be used but this must be checked and GSD of HMI must exists. 

Hello,

then you need check documentation to your expected WinCC RT Advanced version what connection channels are available via which interfaces.