Requirements for serial download to the muTr FPGA from ArcNet
    for the calibration system - M.J. Leitch 3/1/00
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This download is necessary in order to make the data self-describing
in terms of the calibration configuration. The calibration configuration
includes one bit to specify calibration is enabled, 8 bits for the DAC that
sets the amplitude of the calibration pulse, and 64 bits that specify
which anodes are being pulsed. This is a total of 73 bits. These bits should  
be loaded as part of the serial string that is sent to the FPGA  
via ArcNet and they will then be inserted into the data packets
in the user words by the FPGA code. Specifically I would like them
to be inserted in the following words in the packets:                                                     
                                                                
1st userword    least-significant-bit - on for calibration enabled
                  (off when not enabled)
1st userword    next 8 bits - DAC value                              
2nd userword    first 16 bits of 64 bit anode "mask"                 
3rd userword    second 16 bits of 64 bit anode "mask"                
4th userword    third 16 bits of 64 bit anode "mask"
5th userword    fourth 16 bits of 64 bit anode "mask"