MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
1141
Preliminary—Subject to Change Without Notice
Figure 25-17. Decimation Filter/eQADC interface
25.8
Filter Example Simulation
It was checked the decimation filter block operation in a Verilog simulation by using calculated filter
coefficient values and a noisy input data. The expected output values was calculated and the RMS error
was calculated.
25.8.1
Coefficients Calculation
The coefficients were calculate using the Digital Filter Design tool of the SPW software. We have supplied
some hypothetical filter parameters to the tool and obtained the filter coefficients. The input parameters
are:
•
Filter characteristics: Elliptic/Low Pass.
•
Filter type: 4th order IIR.
•
Input sample rate: 800k sample/s.
•
Passband edge: 100 kHz.
•
Stopband edge: 150 kHz.
•
Passband attenuation: <= 1 dB.
The software tool gives the IIR filter coefficients in the rational polynomial format expressed by the
Equation 4 below:
eQADC
CFIFO
BUFFER
CAL
FIFO
CTRL
SERIAL
RFIFO
PSI (m
a
s
te
r)
Decimation Filter
Sky Blue
PSI (slave)
ADC
(analog)
Filter
coefficients
control