Decimation filter configuration register
| DF_CIC_DEC_FACTOR | |
| DF_CIC_DHF | CIC filter decimator half factor |
| DF_ITP1P2 | 1.2 fractional interpolator enable |
| DF_I_U2S | select signed/unsigned format for input |
| DF_O_S2U | select signed/unsigned format for data output |
| PDM_RATE | select the PDM clock rate. |
| DF_MICROL_RN | left/right channel selection on digital microphone |
| DF_HPF_EN | high pass filter enable. |
| DF_HALF_D_EN | half dynamic enable. |