A versatile Timing System based on OS9 for the Spanish stellarator TJ-II

We describe the Timing System for the TJ-II Stellarator, which is presently under construction in Madrid (Spain), and which is expected to start operation in 1996. The Timing System is an essential element of the TJ-II, that has been commissioned, designed, and built to provide synchronization for all the subsystems, diagnostics and auxiliary heating systems of TJ-II. Its structure is both centralized and distributed. The PSK (phase shift keying) modulation technique is used to distribute simultaneously both timing and event information via fiber optic link. The system provides absolute timing references with a variable time resolution ranging from 500 ns to 1 ms, depending on the span time selected, but in all cases, with a precision of 500 ns. The system allow a wide variety of programmable operating modes and control features to be configured easily in a user friendly environment. These are used to generate the sequence of signals required during each experimental pulse. In addition a new set of libraries and C programs named TEMPO have been developed for the OS9 real time operating system, and a set of VME cards has been designed. Remote access via ethernet LAN and multi-user capabilities are also provided. The Timing System has been fully developed by the TJ-II Monitoring and Control Team at CIEMAT. This paper outlines the detailed design of the hardware and software and gives results from the test phase.