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    User name R. Michaels

    Log entry time 19:35:26 on September 17, 2009

    Entry number 290177

    This entry is a followup to: 290167

    Followups:

    keyword=CH scaler (again)

    Since this does not happen in Inj crate or Left or Right crate, it must
    be a mysterious "crate problem". The CRL code is shared.

    The evidence is that the chance of getting stuck is of order 0.1 and
    then the scaler either stays bad for an entire run, or stays good for
    an entire run. If this is wrong, please correct me because it affects
    the following proposal !! (Look at entire runs to tell !!) I remind
    you that 15 runs were good during day shift !

    Getting stuck means the FIFO has no data because no LNE is seen.
    Therefore the static array "sdata" does not update.

    It seems the problem occurs in "go" where the scaler is setup and
    cleared. Note, the LNE is free-running, so even in "go" the scaler
    sees data. Therefore, a possible workaround is to loop N times in
    "go" -- for the CH crate only -- which costs ~10*N microseconds -- and
    in each loop we setup/clear the scaler and check if the FIFO has data
    or not, and repeat the loop until it does. This might reduce the
    probability to (0.1)^N. It sounds crazy but is the only solution I
    can think of. If you want me to try this let me know.



    A copy of this log entry has been emailed to: silwal@jlab.org