ovf_sat.asm

TI的DSP C55X的应用程序

;
;   ovf_sat.asm
;                
;   perform add and sub with and without overflow protection  
;

    .def	_ovftest      
	
    .bss	buff,(0x100)	
    .bss	buff1,(0x100)		

;
;   Code start
;

_ovftest         
    bclr    SATD           ; Clear saturation bit if set  
    xcc     start,T0!=#0   ; If T0!=0, set saturation bit
    bset    SATD
	
start	        
    pshboth XAR5           ; Save XAR5 
    nop
    nop
    mov     #0,AC0	
    amov    #buff,XAR5     ; Set buffer pointer
    rpt     #0x100-1       ; Clear buff
    mov     AC0,*AR5+

    amov    #buff1,XAR5    ; Set buffer pointer
    rpt     #0x100-1       ; Clear buff1
    mov     AC0,*AR5+
	
    mov    #0x80-1,BRC0    ; Initialize loop counts for addition
    amov   #buff+0x80,XAR5 ; Initialize buffer pointer
	
    rptblocal add_loop_end-1
    add    #0x140<<#16,AC0 ; Use upper AC0 as a ramp up counter
    mov    hi(AC0),*AR5+   ; Save the counter to buffer
add_loop_end 

    mov    #0x80-1,BRC0    ; Initialize loop counts for subtraction
    mov    #0,AC0           
    amov   #buff+0x7f,XAR5 ; Initialize buffer pointer	
    rptblocal sub_loop_end-1
    sub    #0x140<<#16,AC0 ; Use upper AC0 as a ramp down counter
    mov    hi(AC0),*AR5-   ; Save the counter to buffer
sub_loop_end

    mov    #0x100-1,BRC0   ; Initialize loop counts for sinewave
    amov   #buff1,XAR5     ; Initialize buffer pointer	
    mov    mmap(@AR0),BSA01; Initialize base register
    mov    #40,BK03        ; Set buffer as size 40 
    mov    #20,AR0         ; Start with an offset of 20 samples
    bset   AR0LC           ; Active circular buffer

    rptblocal sine_loop_end-1
    mov    *ar0+<<#16,AC0  ; Get sine value into high AC0
    sfts   AC0,#9          ; Scale the sine value
    mov    hi(AC0),*AR5+   ; Save scaled value
sine_loop_end

    mov     #0,T0           ; Return 0 if no overflow 
    xcc	    set_ovf_flag,overflow(AC0)   	
    mov     #1,T0           ; Return 1 if overflow detected
set_ovf_flag	

    bclr    AR0LC           ; Reset circilar buffer bit
    bclr    SATD            ; Reset saturation bit	 
    popboth XAR5            ; Restore AR5
	
    ret
	
    .end