Object Id

Each object possesses an ID, with whose assistance the function blocks address the individual objects. You will find the ID in the same dialog in the TwinCAT Building Automation Manager in which the name of the object is also specified. This ID is also specified as an input parameter for each function block. The connection between the function block and the configured object in the TwinCAT Building Automation Manager is established with the help of this ID.

Each ID begins with 1. The upper limit can be freely specified by defining certain constants in the PLC. Further information on the constants can be found in the Appendix.

In the TwinCAT Building Automation Manager, the upper limit for each object type is displayed in the application program area under the Performance features dialog. Note that only objects that were created and activated in the TwinCAT Building Automation Manager can be addressed from the PLC. The PLC block returns an error message if an attempt is made to address an object that does not exist, has not yet been activated or whose ID lies outside the permitted range. Also, the objects can be addressed only if the entire application program is in the RUN state.