At the input to the CIC filter there is a scaling circuit (CIC_SCALE). The scaling down factor is: 2^(SHIFT+SCALE+6*BIG_SCALE-62). I'm using CIC_Decimation of 400, SHIFT=4, SCALE=2, BIG_SCALE=2. The resulting CIC_SCALE is 2^(-44). Does it mean that the input word is shifted down by 44 bits? Do we loose this bits? Does it mean that there is bits truncation at the input to the filter? In the data sheet there is no explanation of the CIC_SCALE circuit and I cannot figure out what happens to the input bits after the CIC_SCALE is applied. Do we loose the least significant bits?? We have only 20 bits at the input to filter!
Please help me to figure out this troubling issue!
Thanks in advance,
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