the 44780 to which you refer is the dsignation of the controller type that's on the LCD PCB. It's either a Hitachi HD44780, or something based on it, so its datasheet is probably as good a reference as you'll need.

This tutorial to which you refer isn't exactly wrong, but it's somewhat ambiguous.

The comment that the EN line "is used to tell the LCD that you are sending it data" is somewhat misleading.

The E signal tells the HD44780 that you're communicating with it.

The remark that, "Only one instruction ("Get LCD status") is a read command. All others are write commands--so RW will almost always be low." is also misleading. There are numerous cases in which you might want to read from the LCD controller IC. One of these is to monitor the busy status, which is the MSB of the lower port, i.e. the location you read when RS is low while R/W (which, actually, is just a nWr signal) and E is held high long enough for you to read the data, after which you should lower the E signal again.

I'd recommend you read the datasheet. Here's a link.

http://www.optrex.com/SiteImage...D44780.pdf
Keep in mind, too, that Hitachi has long been a second source for the Motorola line of 8-bit MCU's, and has a few similar parts that are unique to them, but which behave much like the Motorola parts. They, coincidentally, have a control structure that works hand-in-glove with these LCD's, i.e. they use an E strobe and produce a R/W signal that's similar to what the LCD controller wants. A0 will work for RS as well. The interface works similarly to the MC6845, actually.

In the meantime, take the user-supplied bits of information (including this one) with a grain of salt.

RE