This is exactly what I didn't want. By doing this I can't use the processing cycles while the display is busy, because I have to count the needed time. The project is working this way now, but it is ugly. I wanted to send a character to display and do some other thing while the lcd is busy, then I have to worry about it only when the next character is going to be displayed. And the delay for a lcd reset or clear is so big that I should do something like:

mov a, #0
djnz a, $
djnz a, $
djnz a, $
djnz a, $
djnz a, $

This is what I call ugly... And I can't use the builtin timers because they are already used.