exp4c55_2.asm

用dsp解压mp3程序的算法

**************************************************************
* exp4c55_2.asm - An assembly program for C55x CCS simulator
*                 Coefficient quantization in Section 4.6.2
*
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* 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
	BCLR	C54CM		; set C55x native mode
	BCLR	AR1LC		; set AR1 in linear mode
	BCLR	AR2LC		; set AR2 in linear mode
        BSET 	SXMD
	BSET 	FRCT		; operate in fractional mode
	BSET 	SATD
	
copy	
	AMOV	#coeff_q15, XAR1    ; AR1 pointing to x0
	AMOV	#init_q15,XAR2	    ; XAR2 pointing to table of data
	RPT	#39                 ; repeat next instruction 40 times
	MOV	*AR2+,*AR1+         ; copy 40 data to coeff_q15

* Add the mult-add 40 data using direct addressing mode

mult_add_q15	
	AMOV	#coeff_q15, XAR2
	AMOV    #yq15, XAR1
	MOV 	#0,AC0
        MOV     #0x7FFF<<16,AC1
        RPT  	#39
	MACM 	*AR2+,AC1,AC0	
        MOV 	AC0,dbl(*AR1)
    
end:
	NOP
	B	end		; stop here