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    User name R. Michaels

    Log entry time 11:22:22 on October31,2013

    Entry number 385856

    keyword=recovering FPGA on CAEN 1495

    At times, for reasons I don't know yet, the CAEN 1495 board
    becomes unusable with the following symptoms

    1. Cannot address it
    2. Programmed MLU logic does not function

    When this happens, putting the VME FPGA to "backup" and power-cycling
    seems to restore the functionality. My impression is this has
    something to do with the VME FPGA which controls how the board
    talks to VME. It seems to be triggered when I write to the USER
    FPGA. I think (but am not sure) the recovery sequence is:

    1. Power off
    2. Put the VME FPGA to backup
    3. Power on
    4. load the USER FPGA
    5. Power off
    6. Put the VME FPGA to standard
    7. Power on.

    It's a bad idea to leave the VME FPGA on backup because if something
    goes wrong it becomes very hard (impossible ?) to recover, according
    to what I'm told.

    It also seems wise to not load the USER FPGA a 2nd time after it
    was successfully loaded once. It stays in NVRAM, and loading a
    2nd time seems to trigger this failure.