dowindow.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
	.list

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	.section .libdsp, "x"

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;
; _VectorWindow: Applies windowing to a vector.
;
; Operation:
;	dstV[n] = srcV[n] * window[n], with
;
; n in {0, 1,... , numElems-1}
;
; Input:
;	w0 = number elements in vector(s) (numElems)
;	w1 = ptr to destination vector (dstV)
;	w2 = ptr to source vector (srcV)
;	w3 = ptr to window vector (window)
; Return:
;	w0 = ptr to destination vector (dstV)
;
; System resources usage:
;	See VectorMultiply.
;
; DO and REPEAT instruction usage.
;	no DO instructions
;	no REPEAT intructions
; plus DO/REPEAT instructions from VectorMultiply.
;
; Program words (24-bit instructions):
;	3
; plus words from VectorMultiply.
;
; Cycles (including C-function call and return overheads):
;	9
; plus cycles from VectorMultiply.
; NOTE that the VectorMultiply source code reports the number of cycles
; including 3 cycles of C-function call overhead. Thus, the number of
; actual cycles from VectorMultiply to add to VectorWindow is 3 less
; than whatever number of cycles it takes a stand alone VectorMultiply.
;............................................................................

	; External symbols.
	.extern	_VectorMultiply			; uses vector multiplication

	.global	_VectorWindow	; export
_VectorWindow:

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

	; Compute windowing as a vector (element-by-ellement) multiply.
	call	_VectorMultiply

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

	return	

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	.end

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; OEF