User Manual

Logical I/O blocks
Addressing the I/O blocks
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BACnet addressing
Peer-to-peer communication
Data can be exchanged via peer-to-peer communication.
The exchange takes place using the BACnet services defined in the BACnet standard. The process employs
mechanisms engineered in CFC which can be tracked in online test mode, but which are based on BACnet
objects and BACnet services.
Engineering
When engineering the exchange of data in CFC, it is important to take note of the following:
● Addressing is via [IOAddr].
● Data is exchanged only between BACnet objects. The attributes of the I/O blocks and pins must be
defined appropriately, and the information must also be made available in the form of a BACnet object.
For this purpose, the attributes of this block or I/O must be defined correctly.
● In BACnet terminology, the I/O block is a client which fetches the required value from an object defined
as the server. This process is carried out using services defined by BACnet, e.g.: The client subscribes
to the relevant object (the server) using the SubscribeCOV service. The server then supplies the value
via the BACnet service COVReporting whenever it changes by the programmed value, COVIncrement.
ReadProperty (polling) is another BACnet service. Here, the value is read at regular predefinable
intervals.
● Addressing is carried out via the Technical Designation (TD). Note, however, that this Technical
Designation must first be made known to the client in the form of a reference address.
● The data is exchanged both within a given automation stations, and across automation stations.
Address syntax
Addressing takes place via the input/output address [IOAddr] and always starts with the prefix "B=".
The BACnet reference address is the same as the Technical Designation (TD) of the value. The BACnet
addressing syntax is as follows:
B=BACnetReference (BACnetConfig)
Example: B=Geb6'Lft3'FanSu'Mot'MntnSwi.PrVal(0)
Polling or COV procedure
The FB variable PollCyc is used instead of the prior BACnetConfig parameter in the I/O address syntax, to
distinguish between COV or polling:
FB variable IOAddr. FB variable PollCyc
BACnetConfig = 0 -> COV (Change of Value)
BACnetConfig = 1…65535 -> Polling in seconds
In an automation station operating as a BACnet device, the maximum number of simultaneously supported
COV subscriptions is limited to 400.
The BACnet Device as BACnet Server supports a maximum of 400 subscriptions from BACnet clients or
from other BACnet devices via the BACnetReference.
A BACnet device operating as a BACnet client can also accommodate a maximum of 100 subscriptions to
other values via the BACnetReference.
If the COV procedure is selected, COVIncrement is used for analog objects to define the value by which the
present value must change to initiate a COV event.
Data output using WriteProperty
Output objects can write their Present_Value to the properties of other objects or command other value or
output object.
Write without priority: Optional address string-Par(P=Number) no available.
Command with priority: Optional address string-Par(P=Number) available.
COV across sites
The value subscribed to must be available in the same BACnet network. Avoid a COV across sites.
The DeviceID is used to access and subscribe freely to values in different BACnet devices (especially in the
case of third-party integration). The syntax is as follows:
B=[DeviceID]Objectname – where the object name can be any string required. The DeviceID is entered in
decimal (instance number or entire ObjectID).