📄 fir16_mac.s.list
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;*********************************************
;* Freescale Semiconductor Inc.
;* (c) Copyright 2001 Freescale Semiconductor Inc.
;* ALL RIGHTS RESERVED.
;*********************************************
;* FILE NAME: fir16.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 .text ;-=Locate the code in the ".text" section.=-
.align 4
.xdef _FIR16_MAC
;******************************************************
;* NAME: void FIR16(struct tFir16Struct* pFIR, Frac16* pX, Frac16* pY, unsigned int n)
;*
;* DESCRIPTION: Computes a Finite Impulse Response for a array of 16-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 array of n data elements.
;* 72(a7) pY - Pointer to the output array of n data elements.
;* 76(a7) d6 n - Length of the input and output arrays.
;* 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.
;******************************************************
_FIR16_MAC
;---=Saving values of used registers.=---
0x00000000: 4fefffc4 lea -60(a7),a7
0x00000004: 48d77fff movem.l d0-d7/a0-a6,(a7)
;---=Moving of most useful parameters from stack to registers.=---
0x00000008: 2c2f004c move.l 76(a7),d6 ;n - Length of the input and output arrays.
0x0000000c: 206f0048 move.l 72(a7),a0 ;pCurY - Pointer to the current Y.
0x00000010: 2a6f0044 move.l 68(a7),a5 ;pX - Pointer to the input array of n data elements.
0x00000014: 246f0040 move.l 64(a7),a2 ;pFIR - Pointer to a data structure containing private data for the FIR filter.
0x00000018: 202a0004 move.l 4(a2),d0 ;N - Length of coefficients vector.
0x0000001c: 2c6a0008 move.l 8(a2),a6 ;pFIR->pFirHistory - History buffer.
;---====== Begin of cycle of getting Y[1]..Y[N-1] ======---
0x00000020: 7201 moveq #1,d1 ; for(i=1;i<N;i++) -=Begin of outer loop (number 1)=-
.FORi1
0x00000022: b280 cmp.l d0,d1 ; -=Comparing "i" with "N"
0x00000024: 64000080 bcc .NEXTi1 ; { -=If (i=>N) then jump to .NEXTi1=-
0x00000028: a13c00000000 move.l #0,acc ; output=0; -=Accumulator initialization=-
0x0000002e: 43f51a00 lea (0,a5,d1.l*2),a1 ; pCurX=pX+i; -=Current sample pointer initialization=-
0x00000032: 2652 move.l (a2),a3 ; pCurCoef=pFIR->pFirCoef; -=Current coefficient pointer initialization=-
;---== Begin of cycle Getting Y[i] ==---
0x00000034: 7400 moveq #0,d2 ; k=0 -=Begin of inner loop=-
0x00000036: 08010000 btst #0,d1 ; -=Testing that "i" is even or not=-
0x0000003a: 6700000c beq .EVENk1 ; -=If "i" is even then jump to .EVENk1=-
;-=we do this omly in case of "i" is odd number=-
0x0000003e: 381b move.w (a3)+,d4 ; -=Getting current coefficient=-
0x00000040: 3621 move.w -(a1),d3 ; -=Getting current sample=-
0x00000042: a8030200 mac.w d3.l,d4.l,<< ; -=Getting first iteration of inner loop=-
0x00000046: 5282 addq.l #1,d2 ; -=Incrementing "k"=-
.EVENk1
0x00000048: 281b move.l (a3)+,d4 ; -=Getting next current coefficient=-
.FORk1 ; for(k=0;k<i;k++) -=Begin of main part of inner loop=-
0x0000004a: b481 cmp.l d1,d2 ; { -=Comparing "k" with "i"=-
0x0000004c: 64000010 bcc .ENDFORk1 ; -=If (k=>i) then jump to .ENDFORk1=-
;-=In one program loop we do two MAC operation = 2 FIR inner loop itteration;
; use move long, parallel filling register,
; predecriment and post increment and use left shifting to get fractional multiplication=-
;-=output+=*pCurX--*(*pCurCoef++)=-
0x00000050: 2621 move.l -(a1),d3 ; -=Getting next current sample=-
0x00000052: a8030240 mac.w d3.u,d4.l,<< ; -=First MAC=-
0x00000056: a89b4283 mac.w d3.l,d4.u,<<,(a3)+,d4 ; -=Second MAC and getting next current coefficient=-
0x0000005a: 5482 addq.l #2,d2 ; -=Incrementing "k" by 2=-
0x0000005c: 60ec bra .FORk1 ; } -=Jumping to .FORk1=-
.ENDFORk1
0x0000005e: 598b subq.l #4,a3 ; -=Restoring pointer to the current coefficient=
;---==Testing that History Buffer is filled => this is not first calling of this function==--
0x00000060: 4aaa000c tst.l 12(a2) ; if(pFIR->iFirHistoryCount>0) -=Testing that pFIR->iFirHistoryCount>0=-
0x00000064: 67000034 beq .NEXTif ; { -=If (pFIR->iFirHistoryCount=0) then jump to .NEXTif=-
0x00000068: 49f60afe lea (-2,a6,d0.l*2),a4 ; pCurHistory=pFIR->pFirHistory+N-2;
0x0000006c: 2401 move.l d1,d2 ; -= k=i.Begin of inner loop=-
0x0000006e: 2e00 move.l d0,d7
0x00000070: 9e81 sub.l d1,d7
0x00000072: 08070000 btst #0,d7 ; -=Testing that "N-i" is even or not=-
0x00000076: 6700000c beq .EVENk2 ; -=If "N-i" is even then jump to .EVENk2=-
;-=we do this omly in case of "N-i" is odd number=-
0x0000007a: 381b move.w (a3)+,d4 ; -=Getting current coefficient=-
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