Rev.01 03-27-17
Page 53 of 67
Compu-Aire
10.4.6
BACNET Parameter Description
Device Instance
This is a number that uniquely identifies a device inside the BACnet® network (the
BACnet® network can also include non-MS/TP BACnet® devices). If two units have the
same Device Instance, identification errors will be generated.
Station Address
This is a number that differentiates the units in the BACnet® MS/TP network. If two
units have the same Station Address, identification errors will be generated. To speed
up the data exchange between the Master units, the Station Address of the Master units
should start from 0 and continue without skipping any numbers.
Max Info Frames
This establishes the maximum number of information packages exchanged, above which
the Master unit will give up control (Token) of the network to another Master unit. It
thus indirectly establishes a sort of priority between the Master units in the network:
high numbers guarantee the Master a higher data exchange volume.
MaxMaster
To speed up data exchange between the Master units, Max Master should be set to the
Station Address of the Master with the highest Station Address. In fact, each Master,
after having used the network, passes over control to the next Master. The Max Master
parameter specifies to pCOnet the address of the network Master with the highest
Station Address: using this parameter, pCOnet will know that there is no other Master
with a higher Station Address than Max Master; pCOnet will then give control of the
network to the next Master, however not beyond Max Master; if no next Master is
found, the cycle will begin again, with control being given to the Master with the lowest
Station Address.
Baud Rate
Data transfer speed. The Baud Rate must be the same for all the devices connected.
Otherwise the exchange of data will generate communication errors. For extended
networks, low baud rates should be specified, as these guarantee less communication
errors. If Baud Rate=76800, make sure the device supports this communication speed.
This baud rate is not supported by the RS232 serial port on a normal PC.
Parameter
Min
Max
Factory
Device Instance
0
4194303
77000
Station Address
0
127
0
Max Master
0
127
127
Max Info Frames
0
255
20
Baud Rate
9600, 19200,
38400,76800
Table 10 - BACnet MS/TP parameters
