firinit.s

dsPIC30系列单片机的DSP算法库

;*********************************************************************
;                                                                    *
;                       Software License Agreement                   *
;                                                                    *
;   The software supplied herewith by Microchip Technology           *
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;   is intended and supplied to you, the Company's customer,         *
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;*********************************************************************

	; Local inclusions.
	.nolist
	.include	"dspcommon.inc"		; FIR filter structure
	.list

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	.section .libdsp, "x"

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;
; _FIRStructInit: initialization of FIR filter structure.
;
; Operation:
;	FIRFilter->numCoeffs = numCoeffs;
;	FIRFilter->coeffsBase = coeffsBase;
;	FIRFilter->coeffsEnd = coeffsBase+numCoeffs-(1 byte);
;	FIRFilter->coeffsPage = coeffsPage;
;	FIRFilter->delayBase = delayBase;
;	FIRFilter->delayEnd = delayBase+numCoeffs-(1 byte);
;	FIRFilter->delay = delayBase;
;
; Input:
;	w0 = h, ptr FIR filter structure (see included file)
;	w1 = numCoeffs;
;	w2 = coeffsBase;
;	w3 = coeffsPage;
;	w4 = delayBase;
; Return:
;	(void)
;
; System resources usage:
;	{w0..w5}	used, not restored
;
; DO and REPEAT instruction usage.
;	no DO intructions
;	no REPEAT intruction
;
; Program words (24-bit instructions):
;	10
;
; Cycles (including C-function call and return overheads):
;	19
;............................................................................

	.global	_FIRStructInit	; export
_FIRStructInit:

;............................................................................

	; Prepare for initialization.
	sl	w1,w5				; w5 = numCoeffs*sizeof(coeffs)
	dec	w5,w5				; w5 =
						;   numCoeffs*sizeof(coeffs)-1

;............................................................................

	; Set up filter structure.
	mov	w1,[w0++]		; FIRFilter->numCoeffs = numCoeffs
					; w0 =&(FIRFilter->coeffsBase)
	mov	w2,[w0++]		; FIRFilter->coeffsBase = coeffsBase
					; w0 =&(FIRFilter->coeffsEnd)
	add	w2,w5,[w0++]		; FIRFilter->coeffsEnd initialized
					; w0 =&(FIRFilter->coeffsPage)
	mov	w3,[w0++]		; FIRFilter->coeffsPage = coeffsPage
					; w0 =&(FIRFilter->delayBase)
	mov	w4,[w0++]		; FIRFilter->delayBase = delayBase
					; w0 =&(FIRFilter->delayEnd)
	add	w4,w5,[w0++]		; FIRFilter->delayEnd initialized
					; w0 =&(FIRFilter->delay)
	mov	w4,[w0]			; FIRFilter->delay initialized

;............................................................................

	return	

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	.end

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; OEF