To ensure a stable and reliable
communication, it is important that only the
Note
termination resistor of the first and last unit
in the BACnet MS/TP segment is cut in.
See fig. 2.
BACnet MS/TP segments must be
provided with at least one set, and no
more than two sets of network bias
Note
resistors. See fig. 2.
The network bias resistors are not
available on the CIM 3XX BACnet module.
Cable length
The maximum recommended cable length within
a BACnet MS/TP segment is 1200 metres (4000 ft)
2
with 0.82 mm
(AWG 18) cable.
The connection between the BACnet modules must
be made by use of a screened, twisted-pair cable
with a characteristic impedance between 100 and
130 .
3.3 Setting the BACnet MAC address
The CIM 3XX BACnet module has two hexadecimal
rotary switches for setting the BACnet MAC address.
The two switches are used for setting the four most
significant bits (SW6) and the four least significant
bits (SW7), respectively. See fig. 5.
Fig. 5
BACnet MAC address
The table below shows examples of BACnet MAC
address settings.
For a complete overview of BACnet MAC addresses,
see the table on page 80.
The BACnet MAC address must be set
Note
decimally between 0 and 127.
BACnet MAC address
8
20
31
127
6
SW6
SW7
SW6
SW7
0
8
1
4
1
F
7
F
3.4 Setting the Device Object instance
number
By default, the CIM 3XX BACnet module uses a
predefined Device Object instance number, which is
227XXX (XXX is the BACnet MAC address).
To use the complete Device Object instance number
range, set SW3 to ON, and set the new Device
Object instance number via a BACnet object in the
software. See fig.
6
and the specific functional
profile.
SW3
Fig. 6
Device Object instance number
DIP switch settings
Device Object instance number
Default (227000 + MAC address)
User-defined (set via BACnet object)
3.5 Setting the BACnet transmission speed
The transmission speed must be set correctly before
the CIM 3XX BACnet module is ready to
communicate with the BACnet network. See fig. 7.
SW4 SW5
Fig. 7
BACnet transmission speed
DIP switch settings
Transmission speed
[bits/s]
9600
19200
38400
76800
SW3
OFF
ON
SW4
SW5
OFF
OFF
OFF
ON
ON
OFF
ON
ON