[問題] timer的問題~
最近拿到了一個timer的code~
如下:
.org 0x0000
ljmp _MAIN
.org 0x0100
_MAIN:
mov A, #10
acall _DELAY
mov DPTR, #0xA003
mov A, #0x82
movx @DPTR, A ;init 82C55 (port A output,port B input)
mov TH0,#0xC3 ;set timer higher byte
mov TL0,#0x50 ;set timer lower byte(0xC350 = 50000)
mov TMOD, #0x01 ;set timer at mode 1(16bits)
mov IE, #0x82 ;enable interrupt
setb TR0 ;start timer
_EXIT:
ajmp _EXIT
_DELAY:
mov R0, A
_DELAY_I:
mov R1, #100 ;R1 = 100
_DELAY_J:
mov R2, #100 ;R2 = 100
_DELAY_K:
djnz R2, _DELAY_K ;if(--R2 != 0) goto DELAY_K
djnz R1, _DELAY_J ;if(--R1 != 0) goto DELAY_J
djnz R0, _DELAY_I ;if(--R0 != 0) goto DELAY_I
ret
.org 0x000B ;timer0 interrupt vector
_TIMER0_ISR:
push ACC
push DPH
push DPL
mov DPTR,#0xA000 ;82C55 port A (LED)
movx A,@DPTR ;read port A into acc.
inc A ;acc++
movx @DPTR,A ;write to port A
mov TH0,#0xC3 ;reload timer higher byte
mov TL0,#0x50 ;reload timer lower byte(0xC350 = 50000)
pop DPL
pop DPH
pop ACC
reti
.end
我想請教的是_TIMER0_ISR:這個部分是怎麼運行的?
因為是初學者~
所以有許多地方不是很理解~
請大家多多見諒~
也請大家多多指教~
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