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 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

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

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

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 !