B-5 Real Input Fft Based On Glenn Bergland Algorithm - Motorola DSP56000 Manual

;Latest Revision — September 30, 1986
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;Perform all FFT passes with triple nested DO loop
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do
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lua
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do
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do
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_end_bfy
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_end_grp
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Isr
IsI
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_end_pass
endm
Figure B-2 Radix 2, In-Place, Decimation-In-Time FFT (Sheet 2 of 2)
Figure B-5 Real Input FFT Based on Glenn Bergland Algorithm (Sheet 1 of 8)
B - 12
BENCHMARK PROGRAMS
#points/2,n0 ;initialize butterflies per group
#1,n2 ;initialize groups per pass
#points/4,n6 ;initialize C pointer offset
#-1,m0 ;initialize A and B address modifiers
m0,m1 ;for linear addressing
m0,m4
m0,m5
#0,m6 ;initialize C address modifier for
;reverse carry (bit-reversed) addressing
#@cvi (@log(points)/@log(2)+0.5),_end_pass
#data,r0 ;initialize A input pointer
r0,r4 ;initialize A output pointer
(r0)+n0,r1 ;initialize B input pointer
#coef,r6 ;initialize C input pointer
(r1)-,r5 ;initialize B output pointer
n0,n1 ;initialize pointer offsets
n0,n4
n0,n5
n2,_end_grp
x:(r1),X1 y:(r6),y0
x:(r5),a y:(r0),b
x:(r6)+n6,x0
n0,_end_bfy
x1,y0,b y:(r1)+,y1
-x0,y1,b a,x:(r5)+
b,a x:(r0),b
-x1,x0,b x:(r0)+,a
-y1,y0,b x:(r1),x1
b,a b,x:(r4)+
a,x:(r5)+n5 y:(r1)+n1,y1
x:(r0)+n0,x1 y:(r4)+n4,y1
n0,b1 ;divide butterflies per group by two
b n2,a1 ;multiply groups per pass by two
a b1,n0
a1,n2
BENCHMARK PROGRAMS
;lookup -sine and
; -cosine values
;preload data
;update C pointer
;Radx 2 DIT
;butterfly kernel
y:(r0),a
b,y:(r4)
a,y:(r5)
y:(r0),b
;update A and B pointers
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