Decimation Filter
Freescale Semiconductor
28-47
PXR40 Microcontroller Reference Manual, Rev. 1
represents the hardware implementation of the Decimation
Filter, which includes the scale factor hardware that compensates for the scaling of the coefficients. The
scale factor, S, is set by the bit field DECFILT_x_MCR[SCAL].
Coefficients
B
0
to
B
4
correspond to DECFILT_x_COEF0 to DECFILT_x_COEF4
Coefficients
A
1
to
A
4
correspond to DECFILT_x_COEF5 to DECFILT_x_COEF8.
The delay taps labelled Tap0 to Tap7 correspond to the memory mapped registers DECFILT_x_TAP0 to
DECFILT_x_TAP7.
Figure 28-23. Fourth Order IIR Filter Implementation Block Diagram
The examples given here implement a filter with the following characteristics:
•
Filter type: elliptic/low pass IIR
•
Filter order: 4th order
•
Input sample rate: 800k sample/s
•
Passband edge: 100 kHz
•
Stopband edge: 150 kHz
•
Passband attenuation:
1 dB
lists the computed coefficients, in real number notation, to achieve the above characteristics.
Z
-1
Z
-1
Z
-1
Z
-1
+
B
2
Tap1
B
4
B
3
Tap2
Tap3
Tap0
B
0
B
1
x(n)
+
A
2
Tap5
A
4
A
3
Tap6
Tap7
Tap4
Scale Factor S
A
1
y(n)
Z
-1
Z
-1
Z
-1
Z
-1
Summary of Contents for PXR4030
Page 1: ...PXR40 Microcontroller Reference Manual Devices Supported PXR4030 PXR4040 PXR40RM Rev 1 06 2011...
Page 30: ...PXR40 Microcontroller Reference Manual Rev 1 Freescale Semiconductor xxx...
Page 40: ...PXR40 Microcontroller Reference Manual Rev 1 xl Freescale Semiconductor...
Page 66: ...Memory Map PXR40 Microcontroller Reference Manual Rev 1 2 4 Freescale Semiconductor...
Page 120: ...Signal Descriptions 3 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Page 860: ...FlexCAN Module 24 50 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
Page 1167: ...Decimation Filter Freescale Semiconductor 28 53 PXR40 Microcontroller Reference Manual Rev 1...
Page 1168: ...Decimation Filter 28 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
