Modbus Addressing TX/RX

I am trying to differentiate between the RX/TX Holding registries on my RTU over TCP Modbus device. Since only values written to tags associated with he RX register can adjust values in the device, I need to distinguish read vs. write tags. Is there any special syntax when writing the OPC item path? [device]HR(n)

In Modbus Holding Registers are Read/Write and Input Registers are Read-only.

Are you referring to something else?

Oh! So can I write my OPC item paths with some pointing to Holding Registers and others to Input Registers?

Sure, as long as the data is actually at those registers in your deviceā€¦