System overview
3.2 Features
PN/BACnet LINK
14 Operating Instructions, 10/2017, A5E39895543-AA
Quantity structure for configuring the PN/BACnet LINK
Limits specified by the PN/BACnet LINK
● The sum of all server objects and the object references on the BACnet devices must not
exceed 1000 (e.g. 400 binary inputs on the server and 600 referenced binary outputs).
● Maximum of 400 server objects.
● Maximum of 126 BACnet devices.
● Maximum of 204 analog inputs or 255 analog outputs on the server
● Maximum of 204 analog inputs or 256 analog outputs on the client
Limits caused by the system configuration as well as communication over PROFINET
When using multiple BACnet clients or mixing client object references and server objects,
the maximum user data length in the PROFINET frame of 1280 bytes is relevant as an
additional criterion. The user data length is exhausted in both directions, for example,
through 255 analog output on the server side plus 255 referenced analog outputs plus
3 binary outputs on the server and client side.
Depending on the PROFINET cycle, the following amount of data can be transferred:
● For a maximum of 1000 binary inputs or binary outputs total or
● For a maximum of 510 analog inputs or analog outputs (no more than 255 per
transmission direction) or
● Combinations of the items listed above
Data bytes required in the frame depending on object type:
Analog input (AI) --- 5 5 --
When using the PN/BACnet LINK on a S7-1200 controller, there is an additional limitation
given by the size of the process image of the CPU. A total of no more than 204 analog
entries is possible here.
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