Product manual

B Protocols TAC Xenta Server – Gateway, Technical Manual
128 (184) Schneider Electric Buildings AB, June 2011
04-00124-06-en
B.2.1 Modbus Slave Networks
A Modbus Slave Network consists of a single master and one or more
independent slaves interconnected by an RS-485 serial link. While the
Xenta 913 is attached to the network it appears as one or more pseudo
slave devices to an external master. Through these pseudo slaves the
master can write values to the corresponding inputs within the control
system, and can also read output values from it. The master and all
slaves on the network must use the same Modbus framing mode (RTU
or ASCII).
Each physical or pseudo slave device must have a unique numeric
address on the network. Slave addresses can be in the range 1 to 247
(address 0 is reserved for broadcasts so it is not normally applicable to
a single device). A maximum of 32 physical slave devices can be phys-
ically connected to a Modbus serial line (the I/Link represents 1 physi-
cal slave regardless of how many pseudo slaves it represents). If more
physical slaves are required one or more RS-485 Network extenders can
be fitted.
The Xenta 913 can be directly connected to the master as the sole slave
device, in which case the connection between them can be RS-232 or
RS-485.
Note
• Regardless of the Modbus network configuration, all connected
slave devices must be assigned a unique numeric address.