vmin.s

dsPIC30F_DSP算法库

;*********************************************************************
;                                                                    *
;                       Software License Agreement                   *
;                                                                    *
;   The software supplied herewith by Microchip Technology           *
;   Incorporated (the "Company") for its dsPIC controller            *
;   is intended and supplied to you, the Company's customer,         *
;   for use solely and exclusively on Microchip dsPIC                *
;   products. The software is owned by the Company and/or its        *
;   supplier, and is protected under applicable copyright laws. All  *
;   rights are reserved. Any use in violation of the foregoing       *
;   restrictions may subject the user to criminal sanctions under    *
;   applicable laws, as well as to civil liability for the breach of *
;   the terms and conditions of this license.                        *
;                                                                    *
;   THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION.  NO           *
;   WARRANTIES, WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING,    *
;   BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND    *
;   FITNESS FOR A PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE     *
;   COMPANY SHALL NOT, IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL,  *
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;                                                                    *
;   (c) Copyright 2003 Microchip Technology, All rights reserved.    *
;*********************************************************************

	; Local inclusions.
	.nolist
	.list

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	.section .libdsp, "x"

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;
; _VectorMin: Vector Minimum Value (and last index with minimum value).
;
; Operation:
;	minVal = min {srcV[n], n in {0, 1,...numElems-1} }
;   residually,
;	if srcV[i] = srcV[j] = minVal, and i < j, then *(minIndex) = j
;
; Input:
;	w0 = number elements in vector(s) (numElems)
;	w1 = ptr to source vector (srcV)
;	w2 = ptr to index of minimum value (&minIndex)
; Return:
;	w0 = minimum value (minVal)
;
; System resources usage:
;	{w0..w5}	used, not restored
;
; DO and REPEAT instruction usage.
;	no DO intructions
;	no REPEAT intructions
;
; Program words (24-bit instructions):
;	13
;
; Cycles (including C-function call and return overheads):
;	14			(if numElems == 1)
;	20 + 8*(numElems-2)	(if srcV[n] >= srcV[n+1], 0 <= n < numElems-1)
;	19 + 7*(numElems-2)	(if srcV[n] <  srcV[n+1], 0 <= n < numElems-1)
;............................................................................

	.global	_VectorMin	; export
_VectorMin:

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

	mov	[w1++],w5			; w5 = srcV[0] (current minVal)
	clr	[w2]				; *w2 = current min value index
	dec	w0,w4				; w4 = numElems-1
	bra	le,_endMin			; no more elements...
_compare:
	mov	[w1++],w3			; w3 = srcV[n+1]
	cp	w5,w3				; srcV[n] < srcV[n+1] ?
	bra	lt,_noUpdate			; yes => no update
_doUpdate:					; no  => do update
	mov	w3,w5				; w5 = (current minVal)
	sub	w0,w4,[w2]			; *w2 = current min value index
_noUpdate:
	dec	w4,w4				; w4 = numElems-n
	bra	gt,_compare			; no more elements...
_endMin:
	mov	w5,w0				; restore return value

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

	return	

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	.end

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; OEF