📄 fir32_mac.s
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;*********************************************
;* Motorola Inc.
;* (c) Copyright 2001 Motorola Inc.
;* ALL RIGHTS RESERVED.
;*********************************************
;* FILE NAME: fir32.s
;*********************************************
;!! These functions are "hand coded" in assembler and
;!! the C source is used as comments for short and clear description.
;!! C code used only for more clear andestending what assembler code do, where it is possible.
// .section .dspcode,4,c ;-=Locate the code in the ".dspcode" section.=-
.section .text ;-=Locate the code in the ".text" section.=-
.ALIGN 4
.XDEF _FIR32_MAC
;******************************************************
;* NAME: void FIR32(struct tFir32Struct* pFIR, Frac32* pX, Frac32* pY, unsigned int n)
;*
;* DESCRIPTION: Computes a Finite Impulse Response for a array of 32-bit fractional data values.
;******************************************************
;* Used registers:
;* 64(a7) a2 pFIR - Pointer to a data structure containing private data for the fir filter
;* 68(a7) a5 pX - Pointer to the input vector of n data elements
;* 72(a7) pY - Pointer to the output vector of n data elements
;* 76(a7) d6 n - Length of the input and output vectors
;* d0 N - Length of coefficients vector(N<=n)
;* d1 i - Counter for outer loop.
;* d2 k - Counter for inner loop.
;* a0 pCurY - Pointer to the current Y
;* a1 pCurX - Pointer to the current X
;* a3 pCurCoef - Pointer to the current coefficient
;* a4 pCurHistory - Pointer to the current element of history buffer
;* a6 pFIR->pFirHistory - History buffer.
;* acc output - Accumulator.
;******************************************************/
_FIR32_MAC:
;---=Saving values of used registers.=---
lea -60(a7),a7
movem.l d0-d7/a0-a6,(a7)
;---=Moving of most useful parameters from stack to registers.=---
move.l #0x00000030,MACSR
move.l 76(a7),d6 ;n - Length of the input and output arrays.
move.l 72(a7),a0 ;pCurY - Pointer to the current Y.
move.l 68(a7),a5 ;pX - Pointer to the input array of n data elements.
move.l 64(a7),a2 ;pFIR - Pointer to a data structure containing private data for the FIR filter.
move.l 4(a2),d0 ;N - Length of coefficients vector.
move.l 8(a2),a6 ;pFIR->pFirHistory - History buffer.
;---====== Begin of cycle of getting Y[1]..Y[N-1] ======---
moveq #1,d1 ; for(i=1;i<N;i++) -=Begin of outer loop (number 1)=-
.FORi1:
cmp.l d0,d1 ; -=Comparing "i" with "N"
bcc .NEXTi1 ; { -=If (i=>N) then jump to .NEXTi1=-
move.l #0,acc ; output=0; -=Accumulator initialization=-
lea (0,a5,d1.l*4),a1 ; pCurX=pX+i; -=Current sample pointer initialization=-
move.l (a2),a3 ; pCurCoef=pFIR->pFirCoef; -=Current coefficient pointer initialization=-
;---== Begin of cycle Getting Y[i] ==---
moveq #0,d2 ; for(k=0;k<i;k++) -=Begin of inner loop=-
move.l (a3)+,d4 ; { -=Getting current coefficient=-
.FORk1:
move.l -(a1),d3 ; -=Getting next current sample=-
; We take only upper word
mac.l d3,d4,<<,(a3)+,d4 ; -=Next MAC and getting next current coefficient=-
addq.l #1,d2 ; -=Incrementing "k"=-
cmp.l d1,d2 ; -=Comparing "k" with "i"=-
bcs .FORk1 ; -=If (k<i) then jump to .FORk1=-
;---==Testing that History Buffer is filled => this is not first calling of this function==--
tst.l 12(a2) ; if(pFIR->iFirHistoryCount>0) -=Testing that pFIR->iFirHistoryCount>0=-
beq .NEXTif ; { -=If (pFIR->iFirHistoryCount=0) then jump to .NEXTif=-
lea (-4,a6,d0.l*4),a4 ; pCurHistory=pFIR->pFirHistory+N-2;
;--------------------------------------------
move.l d1,d2 ; for(k=i;k<N;k++) -= k=i.Begin of inner loop=-
.FORk2: ; {
move.l -(a4),d5 ; -=Getting next current element of history buffer=-
; We take only upper word
mac.l d5,d4,<<,(a3)+,d4 ; output+=*pCurHistory--*(*pCurCoef++) -=MAC and getting next current coefficient=-
addq.l #1,d2 ; -=Incrementing "k"=-
cmp.l d0,d2 ; -=Comparing "k" with "N"=-
bcs .FORk2 ; -=If (k<N) then jump to .FORk2=-
.NEXTif: ;//if(pFIR->iFirHistoryCount>0)
;---== End of cycle of getting Y[i] ==---
move.l acc,d7 ; *pCurY++=output; -=Moving accumulator to general register=-
move.l d7,(a0)+ ; -=Store Y[i]=-
addq.l #1,d1 ;i++ -=Incrementing "i"=-
bra .FORi1 ; -=Jumping to .FORi1=-
.NEXTi1: ; }//for(i)
;---====== End of cycle Y[1]..Y[N-1] ======---
;---====== Begin of cycle of getting Y[N]..Y[n] ======---
move.l d0,d1 ; for(i=N;i<=n;i++) -=Begin of outer loop (number 2)=-
.FORi2:
cmp.l d6,d1 ; -=Comparing "i" with "N"=-
bhi .NEXTi2 ; { -=If (i>n) then jump to .NEXTi2=-
move.l #0,acc ; output=0; -=Accumulator initialization=-
lea (0,a5,d1.l*4),a1 ; pCurX=pX+i-1; -=Current sample pointer initialization=-
move.l (a2),a3 ; pCurCoef=pFIR->pFirCoef; -=Current coefficient pointer initialization=-
;---== Begin of cycle of getting Y[i] ==---
moveq #0,d2 ; for(k=0;k<N;k++) -=Begin of inner loop=-
move.l (a3)+,d4 ; { -=Getting current coefficient=-
.FORk3:
move.l -(a1),d3 ; output+=*pCurX--*(*pCurCoef++); -=Getting next current sample=-
mac.l d3,d4,<<,(a3)+,d4 ; -=MAC and getting next current coefficient=-
addq.l #1,d2 ; -=Incrementing "k"=-
cmp.l d0,d2 ; -=Comparing "k" with "N"=-
bcs .FORk3 ; } -=If (k<N) then jump to .FORk3=-
;---== End of cycle of getting Y[i] ==---
move.l acc,d7 ; *pCurY++=output; -=Moving accumulator to general register=-
move.l d7,(a0)+ ; -=Store Y[i]=-
addq.l #1,d1 ; -=Incrementing "i"=-
bra .FORi2 ; -=Jumping to .FORi2=-
.NEXTi2: ; }//for(i)
;---====== End of cycle Y[N]..Y[n] ======---
;---====== Begin of History Buffer Loading ======---
move.l d6,d7 ; -=pCurX=pX+n-N+1;=-
sub.l d0,d7
lea (4,a5,d7.l*4),a1
move.l a6,a4 ; pCurHistory=pFIR->pFirHistory;
moveq #1,d1 ; for(i=1;i<N;i++) -= i=1 =-
.FORbuf:
cmp.l d0,d1 ; -=Comparing "i" with "N"=-
bcc .ENDbuf ; { -=If (i=>N) then jump to .ENDbuf=-
move.l (a1)+,(a4)+ ; *pCurHistory++=*pCurX++;
addq.l #1,d1 ; -=Incrementing "i"=-
bra .FORbuf ; -=Jumping to .FORbuf=-
.ENDbuf: ; }
subq.l #1,d1 ; pFIR->iFirHistoryCount=N-1;
move.l d1,12(a2) ; }//end -=setting pFIR->iFirHistoryCount by N-1 =-
;---====== End of History Buffer Loading ======---
;-=Restoring values of used registers=-
movem.l (a7),d0-d7/a0-a6
lea 60(a7),a7
rts
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