Time-triggered architecture


Time-triggered architecture, also known as a time-triggered system, is a computer system that executes one or more sets of tasks according to a pre-determined and set task schedule. Implementation of a TT system will typically involve use of a single interrupt that is linked to the periodic overflow of a timer. This interrupt may drive a task scheduler. The scheduler willin turnrelease the system tasks at predetermined points in time.

History and development

Because they have highly deterministic timing behaviour, TT systems have been used for many years to develop safety-critical aerospace and related systems.
An early text that sets forth the principles of time triggered architecture, communications, and sparse time approaches is Real-Time Systems: Design Principles for Distributed Embedded Applications in 1997.
Use of TT systems was popularised by the publication of Patterns for Time-Triggered Embedded Systems in 2001 and the related introductory book Embedded C in 2002. The PTTES book also introduced the concepts of time-triggered hybrid schedulers and shared-clock schedulers.
Since publication of PTTES, extensive research work on TT systems has been carried out.

Current applications

Time-triggered systems are now commonly associated with international safety standards such as IEC 61508, ISO 26262, IEC 62304 and IEC 60730.

Alternatives

Time-triggered systems can be viewed as a subset of a more general event-triggered system architecture.
Implementation of an ET system will typically involve use of multiple interrupts, each associated with specific periodic events or aperiodic events. ET designs are traditionally associated with the use of what is known as a real-time operating system, though use of such a software platform is not a defining characteristic of an ET architecture.