Hybrid change of state protocol

Incorporating CAN into industrial control applications came with challenges, and several improvements to the protocol were required. This patent describes a mixed polling and triggered communication scheme.

In control systems, sometimes you have a choice between polling inputs (checking them periodically), or reacting only when the inputs change. Likewise, a system might refresh its outputs periodically, or only when they change.

While the react-on-change technique offers potentially better performance, in a noisy electrical environment there is potential to miss a transition.  This patent describes a method of combining polling with reactive techniques to maintain high performance while mitigating the effect of missed transitions.