Zero- and one-based addressing

PLCs in which the address of the register is equivalent to the subscribed tag address are known as zero-based PLCs (also written as "0-based"). In zero-based PLCs, the tag 400000 corresponds to the holding register address 00000 in the PLC. In one-based PLCs, the tag 400001 corresponds to the holding register address 00000 in the PLC. The TSX Premium model PLC is zero-based.

To support zero-based PLCs, the MBTCP OI Server has implemented a configurable zero-based and one-based addressing scheme. The TSX Premium, Generic ModbusPLC, and the ModbusPLCRS PLC hierarchies have the zero-based addressing option.

The default addressing scheme in the MBTCP OI Server is one-based.