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Sizes range from 2 lines of 8 characters to 4 lines of 20 characters.
I have a couple here of 4x40, and I've seen them in catalogs with lines up to 2x80.
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it can use a 4-bit data bus which needs only 7 lines for the interface. (An output-only port will have to wait out the display's busy period between commands, whereas a bidirectional connection can poll a busy bit.)
so with a 4-bit interface, you only need 6 port bits, not 7. I'm using 6 on my workbench computer, just leaving enough time that I know each operation is done before doing the next, since I can't read the busy bit.
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Anyone have any experience to share, or specific recommendations?
I've used them many times. I address them at the top of
http://wilsonminesco.com/6502primer/displays.html, which also has a link to some code at
http://wilsonminesco.com/6502primer/LCDcode.asm. This includes the initialization which can trip you up if you're not forewarned about it. For the web page, I simplified the code from what we actually used which loaded a lot of special characters. The different sizes of displays work pretty much the same, with just small differences in how individual characters are numbered. Electrically, 4x40 is really two 2x40's parallelled except for the individual Enable lines brought out so you only talk to one at a time.