The servant-proxy and supervisor-proxy subcomponents have registers with references to data of the same type. The data must be of a certain structure:
Required, used to instruct the servant.
Actual, the actual state or value, and condition of the servant.
You fit the data type of Required and Actual to the application.
When the supervisor wants to send a command to the servant, it writes to Required in the servant proxy register. This will copy the data to Required in the supervisor proxy register and call the supervisor proxy method – Required_changed – within the servant.
When the servant wants to tell the supervisor that data has changed, it writes to Actual in the supervisor proxy register. It will copy the data to Actual in the servant proxy register and call the servant proxy method: Actual_changed in the supervisor.
The system will keep the data in the two registers the same. After a node disconnects from the P-NET, servant power-up, supervisor power-up, or power-up on both, the system will make the data in the registers the same.