The timing system for the ASDEX upgrade experiment control

For the adaptive control system of the ASDEX Upgrade tokamak experiment a new digital timing system was developed. Its structure is centralized and distributed. The timing system defines a systemwide 100 nanosecond absolute timescale by central generation of clock and time zero information. Distributed processes are synchronized by time events and state events generated centrally. The timing system supports preprogrammed operation and as a new feature adaptive operation in close collaboration with the central control computers. A standard modulation technique allows to distribute simultaneously the time and event information via fibre optics cables. The timing system is remote controlled by internal functions using the same fibre optics. This paper summarizes the ASDEX Upgrade timing system design and implementation, and aspects of the integration into the control system