Filter math accelerator (FMAC) RM0440
496/2126 RM0440 Rev 4
Parameters:
• The parameter P contains the length, N+1, of the coefficient vector B
in the range
[2:127].
• The parameter R contains the gain to be applied to the accumulator output. The value
output to the Y buffer is multiplied by 2
R
, where R is in the range [0:7]
• The parameter Q is not used.
The function completes when the START bit in the FMAC_PARAM register is reset by
software.
IIR filter
Y = B*X+A*Y’
This function implements an infinite impulse response (IIR) filter. The filter output vector Y is
the convolution of a coefficient vector B
of length N+1 and a vector X of indefinite length,
plus the convolution of the delayed output vector Y
’ with a second coefficient vector A, of
length M. The elements of Y
for incrementing values of n are calculated as y
n
= B.X
n
+ A.Y
n-
1
, where X
n
= [x
n-N
,...,x
n
] comprises the N+1 elements of X at indexes n - N to n, while Y
n-1
= [y
n-M
,...,y
n-1
] comprises the M elements of Y at indexes n - M to n - 1. The structure of the
filter (direct form 1) is shown in Figure 48.
y
n
2
R
b
k
x
nk–
a
k
y
nk–
k1=
M
+
k0=
N
⋅=
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