www.pudn.com > x28x_FFT.rar > cfft32br2.asm

;======================================================================== 
; 
; File Name     : cfft_br2c.asm 
;  
; Originator    : Advanced Embeeded Control  
;                 Texas Instruments  
;  
; Description   : This file contains source code, to bit reverse the N-point real sequence 
;                 stored in alternate memory locations. 
; 
; Date          : 26/2/2002 
;====================================================================== 
;  
;  
; Routine Name  : Generic Function       
; Routine Type  : C Callable 
;  
; Usage : 
; void FFTC_brev2(int *src, int *dst, ushort n) 
; This function bit reverses the N-point real sequence stored in alternate memory locations  
; to carry out N-point complex FFT computation. If src=dst, then in-place bit reversal is performed. 
; The destination array should be aligned to 2N words.  
;===================================================================== 
; INPUT ARRAY 
;         |Xr(0)| 
;         |Xi(0)| 
;         |Xr(1)| 
;         |Xi(1)| 
;            : 
;            : 
;===================================================================== 
 
                .def _CFFT32_brev2 
  
_CFFT32_brev2:   
                                    ; XAR4->src, XAR5->dst, AL=size 
            MOVL    XAR0,XAR4       ; XAR0->src 
            NOP     *,ARP5 
             
            CMPR    0               ; TC=1, if src==dst 
            BF      off_place,NTC   ; If not equal, jump to off place bit rev 
 
; IN-PLACE BIT-REVERSAL 
in_place: 
            MOVZ    AR7,AL          ; AR0=size 
            SUBB    XAR7,#1         ; XAR7=size-1 
            LSL     ACC,#1          ; ACC=2*size 
            MOVZ    AR6,AL          ; AR0=2*size 
             
next_data1:  
            MOVL    XT,*XAR4        ; XT=*src 
            MOVL    P,*XAR5         ; P=*dst 
            MOVL    XAR0,XAR4       ; XAR0=src 
            CMPR    2               ; check srcsrc+2, AR7=AR7-1 
            LRETR 
             
; OFF-PLACE BIT-REVERSAL             
off_place:   
            MOVZ    AR7,AL          ; AR0=size 
            SUBB    XAR7,#1         ; XAR7=size-1 
            LSL     ACC,#1          ; ACC=2*size 
            MOVZ    AR0,AL          ; AR0=2*size 
             
next_data2: MOVL    ACC,*XAR4++     ; XAR4=src+1, ACCL=*src 
            ADDB    XAR4,#2         ; XAR4=src+2 
            NOP     *,ARP5          ; ARP=XAR5 
            MOVL    *BR0++,ACC      ; XAR5=br(dst+size) 
            BANZ    next_data2,AR7--                  
            LRETR