> What is the default for the screen on power up ?

An HD44780 addresses the first-line character locations by default
and they will show as filled blocks. Presumably they are showing
ASCII 0 with FF data in the CGRAM. It almost appears intentional
so that the user isn't confronted with a blank screen on power-up.
Maybe it's just the way the silicon powers up, the same way a PIC's
RAM does.

For a 16x2 this will be the top line. The lower line of 16 will not
show, not even have any contrast, until after initialisation, as you
need to be able to set the address register to access them. The
data is passed to the second-line driver, usually an HD44100.=20

That's as I understand it anyway. COB is making it hard to tell
exactly what's on the board now. I can only refer to my older
screens - a 16x1 has just an HD44780, a 20x2 has an HD44780
and two HD44100 and so on. A very old laptop LCD, resolution
of which I forget, has quadrants driven by HD44780/HD44100

I'm not aware of an LCD that shows characters on power-up.
It would be easy for the manufacturer to embed a small micro
to initialise the screen and include a message etc but unnecessary
$$$$$ for the consumer.

Joe
--=20
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