I try the method as you suggested by writing the code that combine real time clock program with LCD.

ASCIIS1:
MOV B,#10
DIV AB
ADD A,#30h
ret

ASCIIS2:
MOV B,#10
DIV AB
MUL AB
MOV R0,A
MOV A,SECONDS
SUBB A,R0
ADD A,#30h
ret

; I've interrupt routine that produce SECONDS variable here

MAIN:

; I've the main program that produce SECONDS variable here

trick:
LCALL INIT_LCD
LCALL CLEAR_LCD

mov A, SECONDS
LCALL ASCIIS1
LCALL WRITE_TEXT

mov A, SECONDS
LCALL ASCIIS2
LCALL WRITE_TEXT

sjmp trick
END

The display start off pretty well with 00 then start to count up as seconds pass -> 01 -> 02 ....

Then when it reach 10+, first digit(I mean left digit) still display correctly but the right digit go crazy. like this -> 1:

Then when it reach 20+ it become something like this -> 2B -> 2F ->....

Since right digit is "once"(I mean 0-9 period) display correctly the code is suppose to be correct.

May I ask waht I did wrong?

Thank you ^_^