Time-triggered architecture
A system design in which everything happens at predetermined instants on a global clock, rather than in response to events.
The idea is associated with Hermann Kopetz at TU Wien, who championed it from the late 1970s onwards. An event-triggered system reacts to interrupts as they arrive, which makes its behaviour under heavy load hard to predict. In a time-triggered system every node and every message owns a fixed slot in a cyclic schedule; a node with nothing to say transmits anyway, so a missing message is noticed immediately.
The TTP protocol and later TTEthernet were commercialised by the spin-off TTTech and have flown in the Airbus A380, the Boeing 787 and NASA's Orion capsule. The drawback is rigidity: adding one function can mean recomputing the whole schedule. The automotive FlexRay bus borrowed much of the thinking.