There are instances where a Modbus TCP device contains several unit numbers at the same IP address.
This is common in a multi-channel device where unit specifies channel number. Since RTU does not have
the luxury of this sort of multi-layer addressing, your RTU master will need a way of seeing each channel
as a separate RTU slave address. The non-mapping gateway can do this for you. We say
"non-mapping" because there is no register or object mapping common to other gateways. But RTU slave
addresses are being mapped, so in that sense, the non-mapping gateway is still doing some form of
mapping.
The example below shows RTU slave addresses 1 through 5 being sent to the first IP address in the list,
and unit numbers on the TCP side will be sent as 1 through 5, corresponding to RTU slave addresses 1
through 5. The second line shows RTU slave addresses 6 through 10 being sent to the second IP address
on the list, and unit numbers on the TCP side will be sent as 1 through 5 corresponding to RTU slave
addresses 6 through 10.
3. Configuring Gateway as a Modbus RTU Master
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