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TTC signals: Global Trigger and Global Muon Trigger

TTC signals: Global Trigger and Global Muon Trigger. Manfred Jeitler TTC Meeting 3 October 2006. the Global Trigger as source of TTC signals. Global Trigger has to receive clock and orbit signal from TTCci over fiber, or from TTCmi over Lemo cables

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TTC signals: Global Trigger and Global Muon Trigger

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  1. TTC signals:Global TriggerandGlobal Muon Trigger Manfred Jeitler TTC Meeting 3 October 2006

  2. the Global Trigger as source of TTC signals • Global Trigger has to receive clock and orbit signal • from TTCci over fiber, or • from TTCmi over Lemo cables • Trigger Control System (TCS) produces L1A and BGO signals • at start of run • orbit counter reset, event counter reset, resynch, start • at end of run • stop • for resynch during run, hard reset etc • “private” signals for each DAQ partition • all BGO signals are created at specific bunch crossing number • to be selected in TCS, can be different for each DAQ partition • L1AOUT sends L1A and BGOs to all user TTCci’s • send over the (in)famous “Hirose” cables • 8 wire pairs for the 4 BGO bits, L1A, BCRES, clock, strobe

  3. the Global Trigger and Global Muon Trigger as users of TTC signals • the TCS board could distribute triggers and BGOs to all the boards in the GT crate (including GMT) over the backplane • we need these signals for the readout, like everybody else • but we prefer to receive all signals via the fiber from our TTCci • this allows to check right away if the signal distribution works • GT uses TTCci in a “transparent” mode • we want to receive BGO signals in exactly the same way as we send them (same bit patterns) • but everybody is free to program “their” TTCci the way they need/like it

  4. L1A, BGO and clock distribution GT crate L1AOUT TIM TCS GMT TTCmi clock + orbit L1A + BGO L1A, BGOs; clock? TTCci TTCex

  5. the question of the clock distribution • the idea of the TTC group: • get L1As, BGOs and clock from L1AOUT into TTCci • “so there should be no danger of clock shifting with respect to L1A and BGO signals” • TTCci sends this to TTCex, which gets directly the “best possible” clock from TTCmi (or its successor) • detectors need by all means this direct TTCmi clock because the TCS system could introduce a slow drift of up to 2 ns • but: • we really do not expect the clock to shift into the wrong bunch crossing • if this should ever happen, the Global Trigger would notice it right away in its monitoring • but the clock from the TCS may also have a jitter • (on top of a drift) • the TCS was never meant by its designers to distribute a clock ! • so why use this clock at all? • please use TTCmi clock right away in TTCci !

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