A protocol tag is provided to receive data from PLC or to write data to PLC. To add a tag to a device/group manually, use the 'Add. Protocol Tag' command . To import tags to Multi-Protocol MasterOPC Server, execute the 'Add. Protocol Tags (Import)' command from the context menu of a device (see Searching devices and importing tags ).
A BACnet tag has the following main properties:
Object type – type of a BACnet object polled
Object number – number of an object of the specified type
Property type – each BACnet object has a structure of properties. The Property type parameter defines what property should be read out and written to the tag,
During object polling, the Status_Flag property is forced to be polled. This property is a bit mask of 4 states:
State |
Number bit |
Description |
OUT_OF_SERVICE |
0 |
Turns to True (1) if the OUT_OF_SERVICE property is enabled. |
OVERRIDDEN |
1 |
Turns to True (1) if the value has been overridden and can no longer be changed via the Bacnet service |
FAULT |
2 |
Turns to True (1) if the Reliabiltiy property has a value other than NoFaultDetected. |
IN_ALARM |
3 |
Turns True (1) if the Event_State property has a value other than Normal. |
If the Status_Flag property has OUT_OF_SERVICE, FAULT, IN_ALARM bits enabled, the tag with PresentValue property will have Sensor_Failure quality. The OVERRIDEN bit is ignored - its inclusion does not mean channel failure.
Other tag parameters are standard ones (see The Dialog of Tag Parameters ).