CLEARING THE DISPLAY
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When the LCD is first initialized, the screen should automatically be cleared by the 44780 controller. However, it's always a good idea to do things yourself so that you can be completely sure that the display is the way you want it. Thus, it's not a bad idea to clear the screen as the very first operation after the LCD has been initialized.
An LCD command exists to accomplish this function. Not surprisingly, it is the command 01h. Since clearing the screen is a function we very likely will wish to call more than once, it's a good idea to make it a subroutine:
CLEAR_LCD:
SETB EN
CLR RS
MOV DATA,#01h
CLR EN
LCALL WAIT_LCD
RET
How that we've written a "Clear Screen" routine, we may clear the LCD at any time by simply executing an LCALL CLEAR_LCD
WRITING TEXT TO THE LCD
Now we get to the real meat of what we're trying to do: All this effort is really so we can display text on the LCD. Really, we're pretty much done.
Once again, writing text to the LCD is something we'll almost certainly want to do over and over--so let's make it a subroutine.
WRITE_TEXT:
SETB EN
SETB RS
MOV DATA,A
CLR EN
LCALL WAIT_LCD
RET
The WRITE_TEXT routine that we just wrote will send the character in the accumulator to the LCD which will, in turn, display it. Thus to display text on the LCD all we need to do is load the accumulator with the byte to display and make a call to this routine. Pretty easy, huh?
