ADSP-214xx SHARC Processor Hardware Reference
6-39
FFT/FIR/IIR Hardware Modules
The input buffer size for decimation filters is N – 1 + (W
×
M) where:
• N is the number of taps
• W is the window size
• M is the decimation ratio
The window size (
WINDOW
bits) in the
FIRCTL2
register must be pro-
grammed with the number of output samples.
To start this mode, programs set the
FIR_RATIO
and
FIR_UPSAMP
bits in the
FIRCTL2
register (along with normal filter setting). Also the
TAPLEN
bits
setting should be greater than or equal to
FIR_RATIO
bits setting for deci-
mation filter.
Interpolation
An interpolator filter provides L output results for each new input sample,
where L is the interpolation ratio. Note that the output rate is L times the
input rate.
In this mode, according to the ratio specified in configuration register,
FIR logic inserts L – 1 zeros between any two input samples (up-sampling)
and then performs the interpolation (through the FIR filter).
Both up-sampling and down-sampling do not support multi iteration
mode. Therefore, the filtering operation can only be done on up to 1024
TAPs and the ratio of up/down sampling can only be an integer value.
In an interpolation filter FIR logic inserts L – 1 zeros between each sample
and the program has to make sure that these zeroes are fully shifted out of
the delay line before moving on to the next channel. This puts a restric-
tion on window size in terms of L –
the sample ratio
as shown below.
WINDOWSIZE
=
n
×
SAMPLERATIO
where n is the number of input samples.
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Содержание SHARC ADSP-214 Series
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Страница 72: ...Notation Conventions lxxii ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 130: ...Programming Model 2 52 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 264: ...Programming Models 3 134 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 290: ...Programming Model 4 26 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 296: ...Programming Model 5 6 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 396: ...Effect Latency 7 28 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 520: ...Programming Model 10 62 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
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Страница 714: ...Programming Model 19 10 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...