12 bit ADC 100MHZ DSO

[larry_tye]

 In this link http://www.ssalewski.de/DAD.html.en  
I found a 12 bit 100M sample rate of dso using xilinx fpga and atmel usb controller . 12 bit ADC data are passed to fpga but only 8 bit data from fpga passed to usb controller , I wonder to know how 12 bit data "shorted" to 8 bit data ?

[DreamCat]

bit shift, divide to two byte, and transmit twice.