"Embedded processing" is used throughout SUSI. Every major subsystem has an associated, dedicated computer (the device controller) which implements all the logical functions needed to operate the subsystem. The device controllers also communicate with their associated user interfaces. These are application programs which present a common menu-driven interface to the observer. The interface passes commands and exchanges data with its device controller.
The SUSI timebase is a master rubidium oscillator which controls a disciplined quartz crystal oscillator. The epoch of the rubidium clock is currently established by comparison with GPS, and we anticipate replacing the existing time system in the near future with an entirely GPS based system.
The control of SUSI during an observation involves several servo loops. These are time-critical operations and run under a specially developed real-time operating system. Control of each servo system is by a master serial controller linking the relevant device controllers. The master controllers have user interfaces, similar to those for the individual device controllers, which enable the observer to monitor and control the behaviour of the various servos.
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