Analog Devices SHARC ADSP-214 Series Hardware Reference Manual page 332

FIR Accelerator
Single Rate Input Filtering
The total size of the input buffer should at least be equal to N – 1 + W. If
the input buffer that needs to be processed is:
x[n],x[n+1],x[n+2]
....
x[n+W-1]
it should be stored in the memory as
x[n-(N-1)], x[n-(N-2)]
....
x[n-1], x[n], x[n+1]
....
x[n+W-1]
and IIFIR should point to
Decimation
Assuming M = decimation ratio, the total size of the input buffer should
at least be equal to
is
x[n],x[n+1],x[n+2]....x[n+WxM-1]
it should be stored in the memory as
x[n-(N-1)], x[n-(N-2)]....x[n-1], x[n], x[n+1]....x[n+WxM-1]
and IIFIR should point to
Interpolation
Assuming L= interpolation ratio, the total size of the input buffer should
at least be equal to Ceil
If the input buffer that needs to be processed is
x[n], x[n+1], x[n+2]....x[n+W/L-1], and K= Ceil((N-1)/L)
it should be stored in the memory as:
6-36
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x[n – (N – 1)]
. If the input buffer that needs to be processed
N–1+WxM
,
x[n-(N-1)]
((N–1)/L)+W/L
ADSP-214xx SHARC Processor Hardware Reference
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