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The first column, "First RTU Address In", should be the RTU slave address that you
want the gateway to respond to. Assuming you do not want to translate addresses as
they pass through the gateway, the First RTU Address Out would be the same address.
The count ("No. Units at this IP") for a one to one association is simply one. Then
select IP address type, enter that address in notation standard for the address type,
and port number. The standard port normally reserved for Modbus TCP is 502. If no
port is given, the gateway will use 502 by default. A non-standard port number can
also be used.
An example for mapping an IPv6 address is illustrated below.
Each device must have a unique RTU address on the RTU network. Therefore, when
mapping multiple TCP servers as RTU slaves, the First RTU Address In should be the
unique RTU address you want to associate with a specific TCP device.
The First RTU Address In is the address to which the gateway will respond as an RTU
slave. But the TCP servers may all expect to see unit number one in the request (or
some other specific unit). In this case, the "First RTU Address Out" should be the
address that the TCP server wants to see. The RTU address in the incoming request
will be replaced with the First RTU Address Out in the request that is forwarded to the
TCP server.
5. Accessing TCP Devices from RTU
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