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rfft32br.asm
;========================================================================
;
; File Name : rfft_brc.asm
;
; Originator : Advanced Embeeded Control
; Texas Instruments
;
; Description : This file contains source code to suffle the 2N-point real sequence
; as N-point complex sequence in bit reversed order
;
; Date : 26/2/2002
;======================================================================
;
; Routine Type : C Callable
;
; Usage :
; void rfft_brc(int *src, int *dst, ushort n)
; This function shuffles 2N-point in-order array and stores it as N-point complex
; array in bit-reversed order. This is helpful for Real FFT computation on the 2N-point
; real sequence using N-point complex FFT module
;=====================================================================
; SOURCE ARRAY
; | X(0) |
; | X(1) |
; | X(2) |
; | X(3) |
; :
; :
; | X(2N-1) |
;=====================================================================
.def _RFFT32_brev
_RFFT32_brev:
MOVL XAR0,XAR4 ; XAR0->src
NOP *,ARP5
MOV AH,AL ; AH=size
LSR AH,#1 ; AH=size/2
MOVZ AR7,AH ; ZAR7=size/2
SUBB XAR7,#1 ; XAR7=(size/2)-1
CMPR 0 ; TC=1, if src==dst
BF off_place,NTC ; If not equal, jump to off place bit rev
next_data1:
MOVL XT,*XAR4 ; XT=*src
MOVL P,*XAR5 ; P=*dst
MOVL XAR0,XAR4 ; XAR0=src
CMPR 2 ; check src<dst
BF noswap,TC ; if src<dst, do not swap *src & *dst
MOVL *XAR4,P ; *src=*dst
MOVL *XAR5,XT ; *dst=*src
MOVL XT,*+XAR4[2] ; XT=*(src+1)
MOVL P,*+XAR5[2] ; P=*(dst+1)
MOVL *+XAR4[2],P ; *(src+1)=*(dst+1)
MOVL *+XAR5[2],XT ; *(dst+1)=*(src+1)
noswap:
ADDB XAR4,#4 ; XAR4=src+2
MOVZ AR0,AL ; AR0=2*size
NOP *BR0++ ; ; dst=br(dst+2*size)
BANZ next_data1,AR7--
LRETR
off_place:
MOVZ AR0,AL ; AR0=2*size
next_data2:
MOVL XT,*XAR4++ ; XT=*src
MOVL P,*XAR4++ ; P=*(src+1)
MOVL *XAR5,XT ; *dst=*src
MOVL *+XAR5[2],P ; *(dst+1)=*(src+1)
NOP *BR0++
BANZ next_data2,AR7--
LRETR
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