LED    equ P1.0
LEDBuf equ 0

       ljmp    Start

       org     3
Interrupt0:
       push    PSW         ; 保護(hù)現(xiàn)場(chǎng)
       cpl     LEDBuf      ; 取反LED
       mov     c, LEDBuf
       mov     LED, c
       pop     PSW         ; 恢復(fù)現(xiàn)場(chǎng)

       reti

Start:
       clr     LEDBuf
       clr     LED
       mov     TCON, #01h  ; 外部中斷0下降沿觸發(fā)
       mov     IE, #81h    ; 打開(kāi)外部中斷允許位(EX0)及總中斷允許位(EA)
       ljmp    $

       end