Bacnet; Bacnet Objects; Bacnet Services; Bacnet Object Mapping - Siemens FEC920 User Manual

8 BACnet

8.1

BACnet Objects

In BACnet, objects are collections of properties, each representing some bit of information. In addition to
standard defined properties, objects may include vendor-defined properties as long as they function in
accordance with the standard. BACnet also defines the expected behavior from each property for that object.
What makes the object-oriented approach work is that every object and every property as defined by the system
is accessible in exactly the same manner.
8.2

BACnet Services

The process of reading or writing to a property is what BACnet calls a service. Services are the methods used
by any BACnet device when it communicates with another BACnet device, including retrieving information,
transmitting information or communicating an action. The standard defines a wide range of services for
accessing objects and their properties. See Section 8.3.5 for further details.
8.3

BACnet Object Mapping

8.3.1 Mapping to I/O and Loop Data Points

BACnet objects are mapped to FEC920 I/O and Loop data points as shown in Table 2.
Object types are denoted in the table as follows:
AI – Analog Input
AV – Analog Value
BI – Binary Input
BV – Binary Value
CS – Character String
MSI – Multi State Input
Input channels 5-8 are instantiated as BACnet objects if the 'Dual Input Channels' option is set to '05..08'.
Object Name
Channel.1.Main.PV
Channel.1.Alarm1.Threshold
Input Channel 1
Channel.1.Alarm1.Status
Channel.1.Alarm2.Threshold
Channel.1.Alarm2.Status
Channel.2.Main.PV
Channel.2.Alarm1.Threshold
Input Channel 2
Channel.2.Alarm1.Status
Channel.2.Alarm2.Threshold
Channel.2.Alarm2.Status
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FEC920: USER GUIDE
Table 2: BACnet Object Representation of I/O and Loops
A5E45696052A Rev-AA
Type Data Parameter
PV
AI
PV Status
AV AL1 Threshold
MSI AL1 Status
AV AL2 Threshold
MSI AL2 Status
PV
AI
PV Status
AV AL1 Threshold
MSI AL1 Status
AV AL2 Threshold
MSI AL2 Status
Equivalent Modbus Path
Channel.1.Main.PV
Channel.1.Main.Status
Channel.1.Alarm1.Threshold
Channel.1.Alarm1.Status
Channel.1.Alarm2.Threshold
Channel.1.Alarm2.Status
Channel.2.Main.PV
Channel.2.Main.Status
Channel.2.Alarm1.Threshold
Channel.2.Alarm1.Status
Channel.2.Alarm2.Threshold
Channel.2.Alarm2.Status
R/W
R
R/W
R
R/W
R
R
R/W
R
R/W
R
September 18