Enforcing a button press

The HLI has an array of similar control units which command button presses in parallel.

Transfer of GUI requests:

To transfer a request received from the GUI to the PLC, the activated control units are checked in the order of their indices whether the request semaphore is free and the first free request element is used to transfer the button press request to the PLC. The PLC must therefore process the request semaphore request_semaphor_rw for all control units for which the PLC set enable_w to TRUE.