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7 BACnet Communication
3-98
WindO/I-NV4 User’s Manual
7.4 Function
The MICRO/I provides the following functions as a single BACnet device.
• Object and Device Address Binding function
• Read Property function
• Write Property function
• Subscribed COV function
• Unsubscribed COV function
• Foreign Device function
●
Object and Device Address Binding Function
A portion of the properties held by objects created in the MICRO/I can be allocated to device addresses, such as data
registers, and those device addresses can be written to and read.
For example, the analog input value of the MICRO/I can be stored in a data register (#D0000) allocated as
Present_Value of the Analog Input object, and that analog input value can be read by BACnet devices. The analog
output value of the MICRO/I can also be changed from BACnet devices by allocating the data register (#D0004) that
stores the analog output value as Present_Value of the Analog Output object.
The types and numbers of objects can be freely set. The initial values of properties are also set with WindO/I-NV4.
BACnet objects
Initial values of properties
(Set with WindO/I-NV4)
MICRO/I starts running
Device addresses Physical I/Os
BACnet device
Analog
Input object
Present_Value:
10.0
Analog
Output object
Present_Value:
20.0
XXXX object
YYYY object
#D0000: 1000
Coefficient: 0.01
External
analog input:
10 V
Mutually
reflected
External
analog output:
20 mA
#D0004: 1000
Coefficient: 0.02
CH0: 10 V
CH2: 20 mA
MICRO/I Analog I/O module
Read property
Write property
• The processing to mutually reflect properties and device addresses is performed with no relationship to
the processing for parts on the MICRO/I screen. Because device addresses allocated to objects will be
written and read during execution of the processing for parts on the screen, create it so that no
problems will occur when device addresses are referenced or refreshed.
• If a device address changes at an interval which is shorter than the cycle at which changes are reflected
to the property of an object, those changes may not be reflected to the property. To reflect those
changes to the property, keep the values of device addresses for 1 second.
For example, the changes may not be reflected to the property when #M0000, which has been allocated
to Present_Value of a Binary Input object, is turned on for only 10 msec. To reflect those changes to the
property, ensure that #M0000 stays 1 for 1 second.