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ATMEL89S52 开机自检程序（需要电路支持）

  ORG 0000H
    JMP MAIN
    ORG 0013H
    JMP INT1
    ORG 0100H
MAIN:
    MOV SP,#60H
    SETB EA
    SETB EX1
    SETB IT1
    CLR  P2.3
    ACALL DELAY
    SETB  P2.3
    SETB  20H.1
DISPLAY:    
    MOV R1,#08H
    MOV R0,#00H
    MOV DPTR,#TAB
LOOP:
    JNB  20H.1,LOOP
    MOV A,R0
    MOVC A,@A+DPTR
    MOV SBUF,A
WAIT:
    JNB TI,WAIT
    CLR TI
    INC R0
    LCALL DELAY
    DJNZ R1,LOOP
    LJMP DISPLAY
DELAY:
    MOV R6,#08FH
DL1:
    MOV R7,#0F9H
DL2:
    NOP
    NOP
    DJNZ R7,DL2
    DJNZ R6,DL1
    RET
INT1:
    CPL 20H.1
    RETI
TAB:
    DB 0FEH,0FDH,0FbH,0F7H,0EFH,0DFH,0bFH,7FH