VRF Protocol Gateway
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8 BACnet Protocol
8.1 Structure of BACnet Protocol
The structure of BACnet standard protocol is specific to building self-control
system characteristics, a simplified 4-layer structure from OSI 7-layer structure; this
4-layer is corresponding to the application layer, network layer, data link and
physical layer in OSI model. BACnet standard protocol defines its application layer
and network layer, and provides the following 5 solutions to its data link and physical
layers.
BACnet Layers
Equivalent
OSI Layers
BACnet Application Layer
Application
BACnet Network Layer
Network
ISO8802-2
(IEEE802.2) Type1
MS/TP
PTP
LonTalk
Data Link
ISO8802-3
(IEEE802.3)
ARCNET
EIA-485
(RS485)
EIA-232
(RS232)
Physical
8.2 Object and Property of BACnet Protocol
8.2.1 Definition of BACnet Object
BACnet defines a group of o bjects with property to represent any functions of
building self-control equipment, thus provide a standard method to represent
building self-control equipment. The Gateway defines 9 objects, the enumeration
number, name and application sample of these objects are introduced as follows.
No.
Object name
Application sample
0
Analog Input
Sensor input
1
Analog Output
Control output
2
Analog Value
The set valve value or other analog control system
parameter
3
Binary Input
Switch input
4
Binary Output
Relay output
5
Binary Value
Digital control system parameter
13 Multi-state Input
Indicate a multi-state processing program situation, such
as open/close refrigerator and defrosting cycle etc.
14
Multi-state
Output
Indicate a multi-state processing program expectation
status, e.g. started cooling time for refrigerator.
19 Multi-state Value
Indicate a multi-state processing program parameter, such
as AC fan speed setting and mode setting, etc.
Each object has a set of property, the property value describes the features and
functions of the objects.
