Acyclic Data Exchange; Acyclic Reading And Writing Of Properties Of Bacnet Objects From The S7 User Program - Siemens SIMATIC PN/BACnet LINK Operating Instructions Manual

Functions

4.5 Acyclic data exchange

4.5 Acyclic data exchange
4.5.1 Acyclic reading and writing of properties of BACnet objects from the S7 user
program
Using the acyclic PROFINET IO services RDREC (write data record) and WRREC (write
data record), individual "ReadProperty" and "WriteProperty" accesses can be triggered on
any BACnet properties.
The corresponding data records are made available by the PN/BACnet LINK on the client
module.
The S7 user program can perform 16 property accesses in parallel.
A total of 16 data records are available for the two services "ReadProperty" and
"WriteProperty".
The data record indices in use are 0x401 to 0x410.
Note
A data record for a (sub)module in PROFINET is uniquely defined by an "index" that
specifies the data record number. The index is a 32-bit integer. Different data records differ
in their index.
The user can assign priorities to the acyclic "WriteProperty" calls from the S7 user program.
The PN/BACnet LINK supports 16 priority levels.
Note
With property access via the data record mechanism, the PN/BACnet LINK does not adapt
the data format. The conversion of the S7 format (Big Endian) to the data format used on the
BACnet side (Little Endian) must be coded by the user for the property content in the S7
program.
The parameters contained in the following data record structures are also to be specified in
the Big Endian format.
38
Operating Instructions, 10/2017, A5E39895543-AA
PN/BACnet LINK