Download DSP56156 User Manual - Freescale Semiconductor

Freescale Semiconductor, Inc.
APPLICATION EXAMPLES
If a unity gain is expected from the A/D section, the gain of that filter has to be multiplied
by 1/0.9313 in order to compensate the attenuation of the comb filter at the given decimation ratio (refer to Table 6-14).
Table 6-15 Coefficient of the Filter Shown in Figure 6-23
; Source filter file: “compad125-3.IIR.Filter”
_filter_type
_NSTAGES
equ
equ
BIQUAD_FILTER_TYPE
5
; number of biquadratic stages
dc
$0004
Freescale Semiconductor, Inc...
; Biquad stage no. 1
dc
$d100
dc
$6173
dc
$00ce
dc
$2259
; Biquad stage no. 2
dc
$cb98
dc
$5973
dc
$fe9b
dc
$1fd1
; Biquad stage no. 3
dc
$d0af
dc
$6b37
dc
$f992
dc
$1c79
; Biquad stage no. 4
dc
$c4a7
dc
$5669
dc
$d61c
dc
$ea20
; Biquad stage no. 5
dc
$c391
dc
$7c12
dc
$dd40
dc
$e4dd
; g = 0.0002623691665/2
; -d2_1 = -0.7344004701/2
; -d1_1 = 1.522624504/2
; n2_1 = 0.01255399151/2
; n1_1 = 0.5367057372/2
; -d2_2 = -0.8188274379/2
; -d1_2 = 1.39766389/2
; n2_2 = -0.02180931293/2
; n1_2 = 0.4971358354/2
; -d2_3 = -0.7393345338/2
; -d1_3 = 1.675226724/2
; n2_3 = -0.1004858072/2
; n1_3 = 0.4449126054/2
; -d2_4 = -0.9273113361/2
; -d1_4 = 1.350141276/2
; n2_4 = -0.6545527468/2
; n1_4 = -0.34182236/2
; -d2_5 = -0.9442726739/2
; -d1_5 = 1.938610906/2
; n2_5 = -0.5429834643/2
; n1_5 = -0.4240192654/2
Figure 6-24 shows the overall response of the A/D section cascaded with the DSP IIR filter
described above.
MOTOROLA
DSP56156 ON-CHIP SIGMA/DELTA CODEC
For More Information On This Product,
Go to: www.freescale.com
6 - 41