Manual

Installation
2–8 975-0679-01-01 Revision D
Modbus versus
Xanbus
The RS 485 Modbus connection and Xanbus cable connection provide data
communication from the network and devices to the Conext ComBox.
Communication with Modbus devices is handled through the RS 485 or 10/100
Ethernet connection on the Conext ComBox while communication with Xanbus
components occurs through the Xanbus ports of Xanbus-enabled devices.
Connecting the
Conext ComBox
with other Modbus
Devices
In the Modbus implementation, the Conext ComBox acts as a slave to an RS 485
master device. The RS 485 connection to the Conext ComBox allows
communication between the Xanbus network and the master device. This
enables Conext devices to link to third-party software and building management
systems.
If a Modbus device, including the Conext ComBox, is installed as the last device
in a daisy chain, a 120 ohm terminator must be used because they do not have
an internal terminator for the RS 485 network. When inserting two wires in one
terminal, as in the case of daisy-chained RS 485 Modbus devices, use smaller
gauge wires. See the following example.
Note: Turn off all Modbus and other devices prior to wiring the connectors.
24 V 
Power
Supply
See NOTE below.
Modbus
Device 1
RS 485
120-ohm
Terminator
Modbus
Device 2
Modbus
Device 3
Modbus
Device 4
RS 485
120-ohm
Terminator
Connect the
RS 485 connector
to the RS 485 port.
D1
D0
Shield
Conext_ComBox_Owners_Guide.book Page 8 Monday, October 21, 2013 10:00 AM