Motorola DSP96002 - Manual (Page 546)

MOTOROLA DSP96002 USER’S MANUAL B-27
FIR LATTICE FILTER
z
-1
move x:(r0)+,d6.s y:(r4)+,d7.s
fmpy.s d7,d6,d1 x:(r0)+,d4.s y:(r4)+,d5.s
fmpy.s d9,d4,d2
fmpy d5,d4,d0 fadd.s d7,d2 x:(r0)+,d6.s
do #4,_lms_loop
fmpy d9,d6,d3 fadd.s d0,d1 y:(r4)+,d7.s
fmpy d7,d6,d0 fadd.s d5,d3 x:(r0)+,d4.s d2.s,y:(r5)+
fmpy d9,d4,d2 fadd.s d0,d1 y:(r4)+,d5.s
fmpy d5,d4,d0 fadd.s d7,d2 x:(r0)+,d6.s d3.s,y:(r5)+
_lms_loop
fmpy d9,d6,d3 fadd.s d0,d1 d2.s,y:(r5)+
fadd.s d5,d3 (r0)-
move d3.s,y:(r5)+
move y:dsig,d2.s
fsub.s d1,d2
move d2.s,y:e
lms
nop
nop
end
The inner loop updates the coefficients and performs the FIR filtering for a speed of 2N per coefficient.
B.1.17 FIR Lattice Filter
N refers to the number of ’k’ coefficients in the lattice filter. Some filters may have other coefficients other
than the ’k’ coefficients but their number may be determined from k.
K1 K2 K3
∑
∑
∑
∑
∑
∑
z
-1
z
-1
K1
K2 K3
B
(in)
B
(out)
Sx