exp4c54_2.asm

用dsp解压mp3程序的算法

**************************************************************
* exp4c54_2.asm - An assembly program for C5000 CCS simulator
*                 Coefficient quantization in Section 4.6.2
*     
**************************************************************
* Section allocation
*
	    .def    coeff_q15,yq15,init_q15
coeff_q15   .usect  "vars",40   ; reserve 40 locations for coeff

yq15	    .usect  "vars",2	; reserve 2 locations for y

	    .sect   "table"
init_q15    .int    -141,-429,-541,-211,322,354,-215,-551
            .int     21,736,332,-841,-871,755,1651,-304
            .int    -2880,-1106,6139,13157,13157,6139,-1106,-2880
            .int    -304,1651,755,-871,-841,332,736,21
            .int    -551,-215,354,322,-211,-541,-429,-141

	    .text		; create code section
	    .def	 start	; label of the beginning of code

* Copy data to vector x using indirect addressing mode

start:
	NOP
copy:	
	STM	#coeff_q15, AR1	; AR0 pointing to x0
	RPT	#39      	; repeat next instruction 8 times
	MVPD init_q15,*AR1+ 	; copy 8 data to x
	
* Add the mult-add 40 data using direct addressing mode

mult_add_q15:
	.mmregs
	SSBX SXM
	SSBX FRCT		; operate in fractional mode
	RSBX OVM
	STM #coeff_q15, AR2
	RPTZ A, #38
	MAC *AR2+,#7FFFh,A
	SSBX OVM
	MAC *AR2, #7FFFh,A 
	STH A,*(yq15)
	STL A,*(yq15+1)

end:
	NOP
	B	end		; stop here