org 	0
ljmp	1000h
org	000Bh
inc	byte3
reti

org	1000h
... serial port config....
ORL     TMOD,#05H ; init the counter
com:	clr	et1            
	mov     th0,#0 ; reset the counter
        mov     tl0,#0
        mov	byte3,#0
        setb    tr0
	setb	et0
	lcall   dealy_1sec
	clr     tr0
	lcall   display_frec
	sjmp com