exp4c55_3.asm

用dsp解压mp3程序的算法

*********************************************************************************
* exp4c55_3.asm - An assembly program for C55x CCS simulator
*                 Overflow handling of y = sum (xi) i = 1 to 8 in Section 4.6.3
*      
*********************************************************************************
* Section allocation
*
	.def	 x,y,init
x	.usect   "vars",8	; reserve 8 locations for x
y	.usect   "vars",1	; reserve 1 location for y

		.sect	 "table"
init	.int	 19660, 19660, 6554, -9830, -32768, -29491, 9830, 6554
		; Adding these numbers : 0.6+0.6+0.2-0.3-1-0.9+0.3+0.2
		
	.text			; create code section
	.def	 start	; label of the beginning of code

* Copy data to vector x using indirect addressing mode

start
	BSET	C54CM		; set C55x native mode
        BCLR	AR1LC		; set AR1 in linear mode
	BCLR	AR2LC		; set AR2 in linear mode  
	BSET 	SXMD
        BSET 	FRCT  
        BCLR	SATD
    
copy
	AMOV	#x,XAR1		; XAR1 pointing to x0
	AMOV	#init,XAR2	; XAR2 pointing to table of data
	RPT	#7      	; repeat next instruction 8 times
        MOV	*AR2+,*AR1+     ; copy 8 data to x

add:
	AMOV	#x,XAR2		; XAR2 pointing to x0
	MOV	#0,AC0
	RPT 	#7		; set repeat counter to 8 counts
	ADD 	*AR2+<<16,AC0 		
	
* Write the result to memory location y

write
	MOV	HI(AC0),*(#y)	; y <- AC0

end:
	NOP
	B	end