Digital filter for sigma delta modulators (DFSDM) RM0351
632/1693 DocID024597 Rev 3
21.6.3 DFSDM analog watchdog and short-circuit detector register
(DFSDM_AWSCDyR) (y=0..7)
Short-circuit detector and analog watchdog settings for channel y
Address offset: 0x08
Reset value: 0x0000 0000
Bits 31:8 OFFSET[23:0]: 24-bit calibration offset for channel y
For channel y, OFFSET is applied to the results of each conversion from this channel.
This value is set by software.
Bits 7:3 DTRBS[4:0]: Data right bit-shift for channel y
0-31: Defines the shift of the data result coming from the integrator - how many bit shifts to the right
will be performed to have final results. Bit-shift is performed before offset correction. The data shift is
rounding the result to nearest integer value. The sign of shifted result is maintained (to have valid
24-bit signed format of result data).
This value can be modified only when CHEN=0 (in DFSDM_CHCFGyR1 register).
Bits 2:0 Reserved, must be kept at reset value.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16
Res. Res. Res. Res. Res. Res. Res. Res. AWFORD[1:0] Res. AWFOSR[4:0]
rw rw rw rw rw rw rw
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
BKSCD[3:0] Res. Res. Res. Res. SCDT[7:0]
rw rw rw rw rw rw rw rw rw rw rw rw
Bits 31:24 Reserved, must be kept at reset value.
Bits 23:22 AWFORD[1:0]: Analog watchdog Sinc filter order on channel y
0: FastSinc filter type
1: Sinc
1
filter type
2: Sinc
2
filter type
3: Sinc
3
filter type
Sinc
x
filter type transfer function:
FastSinc filter type transfer function:
This bit can be modified only when CHEN=0 (in DFSDM_CHCFGyR1 register).
Bit 21 Reserved, must be kept at reset value.
Bits 20:16 AWFOSR[4:0]: Analog watchdog filter oversampling ratio (decimation rate) on channel y
0 - 31: Defines the length of the Sinc type filter in the range 1 - 32 (AWFOSR + 1). This number is
also the decimation ratio of the analog data rate.
This bit can be modified only when CHEN=0 (in DFSDM_CHCFGyR1 register).
Note: If AWFOSR = 0 then the filter has no effect (filter bypass).
Hz()
1z
FOSR–
–
1z
1–
–
-----------------------------
⎝⎠
⎜⎟
⎛⎞
x
=
Hz()
1z
FOSR–
–
1z
1–
–
-----------------------------
⎝⎠
⎜⎟
⎛⎞
2
1z
2FOSR⋅()–
+()⋅=
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