fftr2fn macro idata,coef,odata
fftr2fn ident 1,0
;
; 1024 Point Complex Fast Fourier Transform Routine
;
; This routine performs a 1024 point complex FFT on external data
; using the Radix 2, Decimation in Time, Cooley-Tukey FFT algorithm.
;
; Real input and complex output data
; Real data in X memory
; Imaginary data in Y memory
; Normally ordered input data
; Normally ordered output data
; Coefficient lookup table
; -Cosine values in X memory
; -Sine values in Y memory
;
; Macro Call - fftr2fn data,coef,odata,ptr1,ptr2
;
; data start of external data buffer
; odata start of external output data buffer
; coef start of sine/cosine table
; ptr1 location of pointer pointing to data acquisition buffer
; ptr2 location of pointer pointing to FFT buffer
;
; Radix 2, Decimation In Time Cooley-Tukey FFT algorithm
; ___________
; | |
; ar,ai ---->| Radix 2 |----> ar',ai'
; br,bi ---->| Butterfly |----> br',bi'
; |___________|
; ^
; |
; wr,wi
;
; ar' = ar + wr*br - wi*bi
; ai' = ai + wi*br + wr*bi
; br' = ar - wr*br + wi*bi = 2*ar - ar'
; bi' = ai - wi*br - wr*bi = 2*ai - ai'
;
; Address pointers are organized as follows:
;
; r0 = ar,ai input pointer n0 = group offset m0 = modulo (points)
; r1 = br,bi input pointer n1 = group offset m1 = modulo (points)
; r2 = ext. data base address n2 = groups per pass m2 =
256 point fft counter
; r3 = coef. offset each pass n3 = coefficient base address m3 = linear
; r4 = ar',ai' output pointer n4 = group offset m4 =
modulo (points)
; r5 = br',bi' output pointer n5 = group offset m5 =
modulo (points)
; r6 = wr,wi input pointer n6 = coef. offset m6 = bit reversed
; r7 = not used (*) n7 = output pointer storage m7 = not used (*)
;
; * - r7 and m7 are typically reserved for a user stack pointer.
;
; Alters Data ALU Registers
; x1 x0 y1 y0
; a2 a1 a0 a
; b2 b1 b0 b
;
; Alters Address Registers
; r0 n0 m0
; r1 n1 m1
; r2 n2 m2
; r3 n3 m3
; r4 n4 m4
; r5 n5 m5
; r6 n6 m6
; n7
; Alters Program Control Registers
; pc sr
;
; Uses 8 locations on System Stack
;
;
; main fft routine
;
_points equ 1024 ;number of FFT points
_intdata equ 0 ;address of internal data workspace
move #idata,r2 ;initialize input pointers
move r2,r0
move #_points/4,n0 ;initialize butterflies per group
move n0,n4 ;initialize pointer offsets
move n0,n6 ;initialize coefficient offset
move #coef,n3 ;initialize coefficient base address
move #_points-1,m0 ;initialize address modifiers
move m0,m1 ;for modulo(points) addressing
move m0,m4
move m0,m5
move #-1,m3 ;linear addressing for coefficient base offset
move #0,m2 ;initialize 256 point fft counter
move m2,m6 ;initialize coefficient address modifier
;for reverse carry (bit reversed) addressing
;
; Do first and second Radix 2 FFT passes as four-point butterflies
;
move x:(r0)+n0,x0 ;initialize butterfly
tfr x0,a x:(r0)+n0,y1 ;
do n0,_twopass
tfr y1,b x:(r0)+n0,y0
add y0,a x:(r0),x1 ;ar+cr
add x1,b r0,r4 ;br+dr
add a,b (r0)+n0 ;ar'=(ar+cr)+(br+dr)
subl b,a b,x:(r0)+n0 ;br'=(ar+cr)-(br+dr)
tfr x0,a a,x0 y:(r0),b
sub y0,a y:(r4)+n4,y0 ;ar-cr
sub y0,b x0,x:(r0) ;bi-di
add a,b y:(r0)+n0,x0 ;cr'=(ar-cr)+(bi-di)
subl b,a b,x:(r0) ;dr'=(ar-cr)-(bi-di)
tfr x0,a a,x0 y:(r4),b
add y0,a y:(r0)+n0,y0 ;bi+di
add y0,b x0,x:(r0)+n0 ;ai+ci
add b,a y:(r0)+,x0 ;ai'=(ai+ci)+(bi+di)
subl a,b a,y:(r4)+n4 ;bi'=(ai+ci)-(bi+di)
tfr x0,a b,y:(r4)+n4
sub y0,a x1,b ;ai-ci
sub y1,b x:(r0)+n0,x0 ;dr-br
add a,b x:(r0)+n0,y1 ;ci'=(ai-ci)+(dr-br)
subl b,a b,y:(r4)+n4 ;di'=(ai-ci)-(dr-br)
tfr x0,a a,y:(r4)+
_twopass
;
; Do remaining 8 FFT passes as four 256 point Radix 2 FFT's using internal data
; and external coefficients.
;
; Each 256 point Radix 2 FFT consists of 8 passes. The first pass
uses external
; input data and internal output data to move the data on-chip. Intermediate
; passes use internal input data and internal output data to keep the data
; on-chip. The last pass uses internal input data and external output data
; to move the data off-chip.
;
move #odata,r4 ;load output data address
do #4,_end_fft ;do 256 point fft four times
move r4,ssh ;push output data address onto stack
move r2,r0 ;get external data input address for first pass
move m2,r3 ;update coefficient offset
move #256/2,n1 ;initialize butterflies per group
move #1,n2 ;initialize groups per pass
do #7,_end_pass ;do first 7 passes out of 8
move #_intdata,r4 ;initialize A output pointer
move n1,r5
move n1,n0 ;initialize pointer offsets
lua (r5)-,n7
move n1,n4
move n1,r6
lua (r0)+n0,r1 ;initialize B input pointer
lua (r4)+n4,r5 ;initialize B output pointer
lua (r6)+,n4
move n4,n5
lua (r3)+n3,r6 ;initialize W input pointer
move n4,n0
;
; initialize butterfly
move x:(r1),x1 y:(r6),y0 ;lookup -sine value
move y:(r0),b
mac x1,y0,b x:(r6)+n6,x0 y:(r1)+,y1
macr -x0,y1,b y:(r0),a ;
do n2,_end_grp
do n7,_end_bfy
subl b,a x:(r0),b b,y:(r4)
mac -x1,x0,b x:(r0)+,a a,y:(r5)
macr -y1,y0,b x:(r1),x1
subl b,a b,x:(r4)+ y:(r0),b
mac x1,y0,b y:(r1)+,y1 ;Radix 2 DIT
butterfly kernel
macr -x0,y1,b a,x:(r5)+ y:(r0),a ;with constant
twiddle factor
_end_bfy
move (r1)+n1
subl b,a x:(r0),b b,y:(r4)
mac -x1,x0,b x:(r0)+n0,a a,y:(r5)
macr -y1,y0,b x:(r1),x1 y:(r6),y0 ;lookup -sine value
subl b,a b,x:(r4)+n4 y:(r0),b
mac x1,y0,b x:(r6)+n6,x0 y:(r1)+,y1
macr -x0,y1,b a,x:(r5)+n5 y:(r0),a ;
_end_grp
move n1,b1
lsr b n2,a1 ;divide butterflies per group by two
lsl a b1,n1 ;multiply groups per pass by two
move r3,b1
lsr b a1,n2 ;divide coefficient offset by two
move b1,r3
move #_intdata,r0 ;intermediate passes use internal
input data
_end_pass
;
; Do last FFT pass and move output data off-chip to external data memory.
;
move n7,r1
move ssh,r4
move (r1)+
move r1,n0
move r1,n1 ;correct pointer offset for last pass
move r1,n4
move r1,n5
move #_points/4,n4 ;offset for output pointer A
lua (r0)+,r1 ;initialize B input pointer
lua (r4)+n4,r5 ;initialize B output pointer, first step
move n4,n5 ;offset for output pointer B
lua (r3)+n3,r6 ;initialize W input pointer
move (r5)+n5 ;initialize B output pointer, second step
move #0,m4 ;bit-reversed addressing for output pointer A
move m4,m5 ;bit-reversed addressing for output pointer B
move x:(r1),x1 y:(r6),y0
move (r5)-n5 ;predecrement output pointer A
move x:(r5),a y:(r0),b
do n2,_lastpass
mac x1,y0,b x:(r6)+n6,x0 y:(r1)+n1,y1 ;Radix 2 DIT
butterfly kernel
macr -x0,y1,b a,x:(r5)+n5 y:(r0),a ;with one
butterfly per group
subl b,a x:(r0),b b,y:(r4) ;and changing twiddle factor
mac -x1,x0,b x:(r0)+n0,a a,y:(r5)
macr -y1,y0,b x:(r1),x1 y:(r6),y0
subl b,a b,x:(r4)+n4 y:(r0),b
_lastpass
move a,x:(r5)+n5 ;save last real result of these 256
move m0,m4 ;reinitialize pointers for modulo addr.
move m0,m5 ;
move m2,r6 ;get fft counter
move n6,n2 ;get fft data input offset
move m3,m2 ;external data pointer uses
linear arithmetic
move (r6)+n6 ;increment fft counter (bit reversed)
move (r2)+n2 ;point to next 256 point fft input data
move r6,m2 ;save fft counter
_end_fft
; when fft is finished, jump back to see if data collection for
next fft is completed
; jmp strt
endm
----------------------------------------------------------------------------------------------------
World Class, Professional, Ethical, and Competent Bug Sweeps, and
Wiretap Detection using Sophisticated Laboratory Grade Test Equipment.
----------------------------------------------------------------------------------------------------
James M. Atkinson Phone: (978) 546-3803
Granite Island Group Fax: (978) 546-9467
127 Eastern Avenue #291 Web:
http://www.tscm.com/
Gloucester, MA 01931-8008 E-mail: mailto:jm..._at_tscm.com
----------------------------------------------------------------------------------------------------
We perform bug sweeps like it's a full contact sport, we take no prisoners,
and we give no quarter. Our goal is to simply, and completely stop the spy.
----------------------------------------------------------------------------------------------------
Received on Sat Mar 02 2024 - 00:57:27 CST