Background Polling

If configured to route telegrams properly, all IP routers on a network will send a message each time a group address is written to by an input device. The driver processes these telegrams and updates the cache value for the group address, thus updating the timestamp, value and quality.

However, the KNX driver does not maintain a continuous connection to each network; there can be multiple KNX to IP routers and it is impossible for Plant SCADA to tell if telegrams from devices have been lost. This means the delivery of on-change notifications can be unreliable.

Because of this, a slow background poll of all group addresses will be conducted. As each group addresses reaches half of the cache life time value a read request will be issued for the group address.