exp4c55_7.asm

用dsp解压mp3程序的算法

*****************************************************************
* exp4c55_7.asm - An assembly program for C55x CCS simulator
*               Special case of multiplication in Section 4.6.7
*
*****************************************************************
* Section allocation
*
	.def	 x,yh,y,init
x       .usect 	 "vars",2   ; reserve 2 locations for x
y	.usect   "vars",1   ; reserve 1 location for y
yh	.usect   "vars",1   ; reserve 1 location for yh

	.sect "table"
init    .int -32768,-32768

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

start
	BCLR	C54CM	    ; set C55x native mode
	BSET 	SXMD
	BSET 	SATD
        BSET 	FRCT 

copy
        AMOV	#x,XAR1	    ; XAR1 pointing to x0
	AMOV	#init,XAR2  ; XAR2 pointing to table of data
	RPT	#1          ; repeat next instruction 2 times
        MOV	*AR2+,*AR1+ ; copy 2 data to x
    
mult
	AMOV	#x,XAR1
	AMOV	#(x+1),XAR2
	MOV 	*AR1<<#16,AC0
	MPYM 	*AR2,AC0

* Write the result to memory location y

write:
	MOV	AC0,*(#y)       ; y <- AL
	MOV 	HI(AC0),*(#yh)	; yh <- AH

end
	NOP
	B	end		; stop here