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    User name R. Michaels

    Log entry time 21:42:56 on March24,2008

    Entry number 228753

    keyword=timing window on L-HRS

    Considerations of timing on L-HRS are only relevant for
    triggers that contain L-HRS info. The L-HRS is read out
    for all triggers but for those with no info the crates
    are empty and timing is irrelevant.

    Let's use T4 at the trigger supervisor as a timing reference.
    T4 happens to be in pretty good shape at the moment, the
    timing window around this is -90 to +85 nsec, meaning if
    T4 slides 90 nsec earlier or 85 nsec later there will be
    good timing. (If too early or too late one gets a "forced
    retiming" which might be undesirable.)

    The same statement now holds for other triggers; they may
    be in that window. Note, this must include the anticipated
    range of accidentals. Those must also be in the window if
    you care about L-HRS. That's why it's best to center the
    true coincidences to within 10 nsec of T4 at trigger supervisor.

    We can, if necessary, the retiming window a bit relative to T4.
    We can slide the L1A earlier by 40 nsec (this makes the -90
    become -50, and the +85 becomes +125).

    I guess we should increase the window some day. Requires
    changing an RC constant I think.