page 132,60,1,1 ;******************************************* ;Motorola Austin DSP Operation June 30,1988 ;******************************************* ;DSP56000/1 ;Port to Memory FFT - 64 point ;File name: D2-56.asm ;************************************************************************** ; Maximum sample rate: 266.54 us at 20.5 MHZ/ 202.37 us at 27.0 MHz ; Memory Size: Prog: 118 words ; Data: 514 words ; Number of clock cycles: 5464 (2732 instruction cycles) ; Clock Frequency: 20.5MHz/27.0MHz ; Instruction cycle time: 97.5ns / 74.1ns ;************************************************************************** ; ; Radix 2 Decimation in Time Fast Fourier Transform Routine ; ; Real input and output data ; Real data in X memory ; Imaginary data in Y ; Normally ordered input data ; Normally ordered output data ; Coefficient lookup table ; -Cosine value in X memory ; -Sine value in Y memory ; ; Macro Call - fftedn1 points,data,odata,coef,ptr1,ptr2 ; ; points number of points (2-32768, power of 2) ; data start of data buffer ; odata start of output data buffer ; coef start of sine/cosine table ; ptr1 location of pointer to block 1 (data collection) ; ptr2 location of pointer to block 2 (FFT computation) ; ; 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 ; ; r4 n4 m4 ; r5 n5 m5 ; r6 n6 m6 ; ; Alters Program Control Registers ; pc sr ; ; Uses 6 locations on System Stack ; ;************************************************************************** ; fftedn1 macro points,data,odata,coef,ptr1,ptr2 fftedn1 ident 1,2 strt move #points,b ;input buffer length loop move r7,a ;get input data pointer sub a,b ;subtract buffer length from current input location move x:ptr1,a ;move input data base addres into a cmp a,b ;see if equal jne loop ;if not, go back ; ; when ready, swap pointers of buffer to be loaded and buffer to be processed ; move x:ptr1,a move x:ptr2,b move b,x:ptr1 move a,x:ptr2 ; ; main fft routine ; move ptr2,r0 ;initialize input pointer move #points/4,n0 ;initialize input and output pointers offset move n0,n4 ; move n0,n6 ;initialize coefficient offset move #points-1,m0 ;initialize address modifiers move m0,m1 ;for modulo addressing move m0,m4 move m0,m5 ; ; Do first and second Radix 2 FFT passes, combined as 4-point butterflies ; move x:(r0)+n0,x0 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 ; ; Perform all next FFT passes except last pass with triple nested DO loop ; move #points/8,n1 ;initialize butterflies per group move #4,n2 ;initialize groups per pass move #-1,m2 ;linear addressing for r2 move #0,m6 ;initialize C address modifier for ;reverse carry (bit-reversed) addressing do #@cvi(@log(points)/@log(2)-2.5),_end_pass ;example: 7 passes for 1024 pt. FFT move ptr2,r0 ;initialize A input pointer move r0,r1 move n1,r2 move r0,r4 ;initialize A output pointer move (r1)+n1 ;initialize B input pointer move r1,r5 ;initialize B output pointer move #coef,r6 ;initialize C input pointer lua (r2)+,n0 ;initialize pointer offsets move n0,n4 move n0,n5 move (r2)- ;butterfly loop count move x:(r1),x1 y:(r6),y0 ;lookup -sine and -cosine values move x:(r6)+n6,x0 y:(r0),b ;update C pointer, preload data mac x1,y0,b y:(r1)+,y1 macr -x0,y1,b y:(r0),a do n2,_end_grp do r2,_end_bfy subl b,a x:(r0),b b,y:(r4) ;Radix 2 DIT butterfly kernel 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 macr -x0,y1,b a,x:(r5)+ y:(r0),a _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 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 a1,n2 _end_pass ; ; Do last FFT pass ; move #2,n0 ;initialize pointer offsets move n0,n1 move #points/4,n4 ;output pointer A offset move n4,n5 ;output pointer B offset move ptr2,r0 ;initialize A input pointer move #odata,r4 ;initialize A output pointer move r4,r2 ;save A output pointer lua (r0)+,r1 ;initialize B input pointer lua (r2)+n2,r5 ;initialize B output pointer move #0,m4 ;bit-reversed addressing for output ptr. A move m4,m5 ;bit-reversed addressing for output ptr. B move #coef,r6 ;initialize C input pointer move (r5)-n5 ;predecrement output pointer move x:(r1),x1 y:(r6),y0 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) 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 ; ; when fft is finished, jump back to see if data collection for next fft is completed jmp strt endm ; ; ; ; interrupt routine org p:$8 movep y:$ffff,y:(r7)+ ;data collection upon interrupt ; ; main routine org p:$100 move #16,a move a,x:$d0 ;store pointer to data block 1 move #80,a move a,x:$d1 ;store pointer to data block 2 move #127,m7 ;set r7 for modulo addressing ; ; call fft macro fftedn1 64,16,144,210,208,209 end