Product manual

TAC Xenta Server – Gateway, Technical Manual B Protocols
Schneider Electric Buildings AB, June 2011 119 (184)
04-00124-06-en
B.1.2 Modbus Master Interface
The Modbus Master interface is added into the network pane of
XBuilder, as shown for a Modsim example network in the following
screenshot.
Interface Properties
• Port Type – In most cases the RS-485 port option will be selected.
The RS-232 option may be suitable for connecting to a single net-
work device such as a router or simulator, but RS-485 will be
required if more than one device is directly connected to the Xenta
913’s serial port.
• Baud Rate, Parity, #Data Bits, #Stop Bits – All the communica-
tion parameters, such as baud rate and parity, must be the same for
all devices on the network.
• Framing Mode – Allows the applicable Modbus framing mode to
be selected (RTU or ASCII). Most Modbus networks use RTU
mode, which is a compact binary form suitable for local area net-
works. The ASCII mode is less compact because it uses 2 charac-
ters per byte, but may be better suited to wider area networks (such
as through modems).
Interface Status Signals
The Modbus Master interface driver generates several network specific
communication status signals, as described below.
• ComsFail – Flags a complete communications failure. Activated
only if communication has failed to all slaves on the Modbus net-
work. Normally caused by incorrect communication property set-
tings, or by faulty wiring of the RS-485 network between the
Xenta 913 and the slave devices.
• OutsFail – Flags if writing to one or more output values has failed
on the Modbus network. Normally a write fails because an incor-
rect register address has been entered.
• InsFail – Flags if reading of one or more input values has failed
on the Modbus network. Normally a read fails because an incor-
rect register address has been entered.