9
ModBus and BACnet Instructions
4
BACnet Con
fi
guration
Addressing
Th
e BACnet local addressing space is comprised of 256
diff erent addresses.
• 255 is reserved for broadcast messages from a
master
device.
•
128 - 254 are free to use for slave devices only.
•
0 - 127 are free to use for master or slave devices.
To set the BACnet local address, the dip switches can be set
in either the 0 position or the 1 position. For switches set to
the 1 position their value will be added together to determine
the address.
Each switch set to the 1 position has the following value:
Dip switch 1 = 1
Dip switch 2 = 2
Dip switch 3 = 4
Dip switch 4 = 8
Dip switch 5 = 16
Dip switch 6 = 32
Dip switch 7 = 64
Dip switch 8 = 128
Any dip switch set to 0 has a value equal to 0.
Example:
To set the address of the BACnet board to 50, dip switches 2, 5,
and 6 have to be set to the 1 position. Th
e address is determined
by adding the values of all the dip switches together.
Address = Value of Dip switch 1 + Value of Dip switch 2 +
Value of Dip switch 3 + Value of Dip switch 4 + Value of Dip
switch 5 + Value of Dip switch 6 + Value of Dip switch 7 +
Value of Dip switch 8
In this example:
Address = 0 + 2 + 0 + 0 + 16 + 32 + 0 + 0 = 50
Th
e BACnet Device Instance is calculated by adding the
BACnet local address to 640000. Using the above example, the
Device Instance will be:
Device Instance = 50 = 640050
Th
e BACnet communication board is equipped with a set of ten dip switches that are used to set the board confi guration (address
and baud rate). Th
e fi rst eight are used to set the address of each board. Th
e ninth and tenth are baud rate.
LED’S
DIP SWITCHES
Figure 4-1
_Communication Board
Since the BACnet communication board is a master device, address 127 is the highest address that can be used.
