ORG 0000H
LJMP MAIN
ORG 000BH
LJMP T0_ISR

BIT1 REG 01H
BIT2 REG 02H
BIT3 REG 03H
BYTE1 EQU 30H
MOD_INIT DB 'ATI',13,10,0

MAIN: CLR A
MOV R0,#7FH

RAM_CLEAR:
MOV @R0,A
DJNZ R0,RAM_CLEAR

CALL SP_INIT
CALL TIMER_INIT
MOV IE,#82h
MOV DPTR,#MOD_INIT
CALL OUT_STR
SJMP $

;*****************************************
OUT_STR: CLR A
L1: PUSH A
MOVC A,@A+DPTR
JZ EXIT
CALL OUT_CHAR
POP A
INC A
JMP L1
EXIT: RET

;****************************************
OUT_CHAR: JNB TI,$
CLR TI
MOV SBUF,A
RET

;****************************************
TIMER_INIT: MOV TH0,#3CH
MOV TL0,#B0H
SETB TR0
RET

;*****************************************
SP_INIT: MOV SCON,#52h
MOV TMOD,#21h MOV TL1,#0
MOV TH1,# -12 SETB TR1 RET
;******************************************
T0_ISR: CLR TR0
MOV TH0,#3CH
MOV TL0,#B0H
DJNZ R0,EXIT2
CPL P0.0
MOV R0,#10

EXIT2: SETB TR0
RETI