Product manual

TAC Xenta Server – Gateway, Technical Manual B Protocols
Schneider Electric Buildings AB, June 2011 137 (184)
04-00124-06-en
B.3.1 Modbus TCP Networks
A Modbus TCP Network consists of one or more clients connected to a
server. The server may act as device containing one or more virtual
slaves, or as a router to a separate RS-485 serial sub-network containing
one or more independent slaves.
While connected to the server over TCP the Xenta 913 acts as a client
to continuously poll the slaves through the server to read the required
data values for use within a control system. It can also write the neces-
sary control system values out to the slaves if applicable. A router, and
all slaves on its sub-network, must use the same protocol mode (RTU or
ASCII).
Each slave device must have a unique numeric address within the
server. Slave addresses on a serial sub-network can be in the range 1 to
247, whereas virtual slave addresses within a Modbus TCP device can
be in the range 0 to 254.
The Xenta 913 and the Modbus TCP server is connected using
10Base-T Ethernet. However, the connection need not be direct, but
may be through any number of routers or bridges on a LAN. It is only
necessary for the IP address of the server to be accessible to the Xenta
913, and for the Modbus TCP port number (normally 502) to be open
for client connections on the server.
Note
• Regardless of the Modbus network configuration, all connected
slave devices must be assigned a unique numeric address.