exp4c55_1.asm

用dsp解压mp3程序的算法

*********************************************************************
* exp4c55_1.asm - An assembly program for C55x CCS simulator
*                 Representing different Q formats in Section 4.6.1
*
*********************************************************************
* Section allocation
*
		.def	 x,y,init_q15, init_q1_14, init_q2_13
x		.usect   "vars",12  	; reserve 12 locations for x
y		.usect   "vars",3	; reserve 3 locations for y

			.sect	 "table"
;init_q15	.int	 0.5*32768, 0.25*32768, 0.125*32768, 0.0625*32768
;init_q1_14	.int	 0.5*16384, 0.25*16384, 0.125*16384, 0.0625*16384
;init_q2_13	.int	 0.5*8192, 0.25*8192, 0.125*8192, 0.0625*8192
init_q15	.int	 16384, 8192, 4096, 2048
init_q1_14	.int	 8192, 4096, 2048, 1024
init_q2_13	.int	 4096, 2048, 1024, 512

		.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  
    BSET	SATD
    
copy	
    AMOV	#x,XAR1		; XAR1 pointing to x0
    AMOV	#init_q15,XAR2	; XAR2 pointing to table of data
    RPT	#11      		; repeat next instruction 12 times
    MOV		*AR2+,*AR1+  	; copy 12 data to x

* Add the first 4 data using direct addressing mode

add_q15:
		
    AMOV	#x,XDP		; XDP pointing to vector x0
    .dp	x			; notify assembler
    MOV		@x,AC0		; AC0 <- x0
    ADD		@(x+1),AC0	; add x1
    ADD		@(x+2),AC0	; add x2
    ADD		@(x+3),AC0	; add x3

* Write the result to memory location y

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

add_q1_14:

	
	MOV	@(x+4),AC0	; AC0 <- x4
	ADD	@(x+5),AC0	; add x5
	ADD	@(x+6),AC0	; add x6
	ADD	@(x+7),AC0	; add x7

	MOV	AC0,*(#y+1)	; y+1 <- AC0
    
add_q2_13:
	
	MOV	@(x+8),AC0	; AC0 <- x8
	ADD	@(x+9),AC0	; add x9
	ADD	@(x+10),AC0	; add x10
	ADD	@(x+11),AC0	; add x11


	MOV	AC0,*(#y+2)	; y+2 <- AC0
	
end:
	NOP
	B	end		; stop here