org 0000H
ajmp MAIN
org 000BH
ajmp CLT0
MAIN:mov TMOD,#01H
mov TH0,#0D8H
mov TL0,#0F0H
mov 40H,#100
mov 20H,#00H
mov 21H,#00H
mov 22H,#00H
setb EA
setb ET0
setb TR0
sjmp $
CLT0:mov TH0,#0D8H
mov TL0,#0F4H
mov A,40H
dec A
mov 40H,A
jnz CLTR
mov 40H,#100
mov A,22H
add A,#01H
da A
mov 22H,A
cjne A,#60H,CLTR
mov 22H,#00H
inc 21H
mov A,21H
da A
cjne A,#60H,CLTR
mov 21H,#00H
inc 20H
mov A,20H
da A
cjne A,#60H,CLTR
mov 20H,#00H
CLTR:ret