IDEC MICRO/I HG4G-CJT22 F-B Series User Manual page 206

7 BACnet Communication
Subscribed COV (COV) function
●
In the COV (Change Of Value) function, the MICRO/I monitors an object for which a report request has been received
from a BACnet device. Then when Present_Value or Status_Flags has changed, the MICRO/I notifies the BACnet
device of the change.
The properties of objects that correspond to the COV function and the timing of when to provide notification of
changes are given as follows.
Object
Analog Input
Present_Value
Analog Output
Status_Flags
Analog Value
Binary Input
Present_Value
Binary Output
Status_Flags
Binary Value
Notification may not be provided for changes in values that are faster than the synchronization cycle of
objects and device addresses.
*1 For example, the following diagram shows when a report request is received from a BACnet device and AI-10 (Analog Input
object, instance number 10) has the status in the following table.
Present_Value
_Increment
COV
BACnet device
(To report requester)
Present_Value of AI-10
has changed to 15.0.
Present_Value of AI-10
has changed to 18.5.
3-100
Properties
Notification of change is provided when (1) or (2) as follows.
When
set for
(1)
notification was sent)
(2) When any of the bits in Status_Flags have changed
Notification of change is provided when (1) or (2) as follows.
(1) When
(2) When any of the bits in Status_Flags have changed
AI-10 Properties
Report request
COV notification
transmission
COV notification
transmission
WindO/I-NV4 User's Manual
Timing to Provide Notification of Change
Present_Value has changed to a value greater than or equal to the value
_Increment (starting point is from when the previous COV
COV
*1
has changed
Present_Value
10.0
3.0
MICRO/I
Present_Value of AI-10: 10.0
COV_Increment: 3.0
Present_Value of AI-10 has changed to 15.0
(Change in Present_Value (5.0) > COV_Increment (3.0))
This change corresponds to timing to provide notification of change (1).
Change in Present_Value = Present value - Value when report request
was received = 15.0 - 10.0 = 5.0
Because COV_Increment = 3.0,
change in present value ≥ COV_Increment has been satisfied.
Present_Value of AI-10 has changed to 17.5
(Change in Present_Value (2.5) > COV_Increment (3.0))
Change in Present_Value = Present value - Value when previous
COV notification was transmitted = 17.5 - 15.0 = 2.5
Change in Present_Value < COV_Increment, and the condition
for timing to provide notification of change (1) is not satisfied.
Therefore, COV notification is not sent.
Present_Value of AI-10 has changed to 18.5
(Change in Present_Value (3.5) > COV_Increment (3.0))
This change corresponds to timing to provide notification of change (1).
Change in Present_Value = Present value - Value when previous
COV notification was transmitted = 18.5 - 15.0 = 3.5
Because COV_Increment = 3.0,
Change in Present Value ≥ COV_Increment has been satisfied.
Value