How to install a Sx2WEB system
10
Example 3: The bus generators SH2MCG24 do not need to be put all together in a DIN rail, and they
can be mixed with the Dupline® modules as is shown in the picture below.
Sx2WEB24 SH2MCG24 SH2RE16A4 SH2RE16A4 SH2MCG24 SH2INDI424 SH2INDI424 SH2MCG24
Also in this case there is no need to wire the RS485 for the HS speed bus since the local bus connector
of the Dupline® modules is transparent to it. The installer only has to terminate the HS speed bus in the
last bus generator of the RS485 network.
1.2.1 Wiring the high speed bus
The high speed bus is an RS485 serial interface, at 256Kbit/s
The cable
The RS485 communication cable is a shielded, twisted pair cable. Many cable manufacturers supply
cable meeting the RS485 standard. Other cabling, such as telephone cable, coaxial cable and multi-
core wires should not be used as they could prove problematic and not provide satisfactory
performance.Cables must be at least 0.5 mm.
Topology
The cable must be installed to pass close by each node. Stubs (cables joining the node to the
cable),stars(multiple cable segments brought back to a single point) or loops must not be used.
Cable length
The maximum length of the cable is 600 metres.
Connection of the cable shield
The shield of the RS485 cable establishes a reference voltage for the RS485 signal conductors.
The "screen pig-tails" going into the terminals should be as short as possible. The shield should be
continuous throughout the installation, the best way is to connect the shield to earth ground in only one
point as nearest as possible to the SH2MCG24 (the best is on the terminal where the cable is
connected). This connection is not to be shared with other devices which could add external noise or
disturbance.
Termination
The network must be terminated at the end on the last bus generator of the network (see the T
terminals in the picture above) while it has already been terminated on the Sx2WEB24 side. This is to
avoid reflections which would disrupt communication.
Cable Insulation
The communication cable must not be run in cable trays carrying power wiring nor in close proximity to
power wiring. Current surges in power wiring due to high equipment starting currents or to faults can
disrupt communication.
For more details please see appendix A.
HSBUS
