DrG.
The datasheets discuss a bare LCD vs an LCD module, which has the LCD attached to a PCB. I bought the LCD module.
The LCD module I have purchased, the MRB3973 is made for dev boards using STM MCUs. I checked each of the listed dev boards and am pretty sure they're all 3.3v logic level.
The LCD module (having a PCB on it) I suppose is essentially a shield for these STM boards, but that's not really useful for me using an Arduino - pinout differences.
If you're using the module with one of those STM dev boards, you can route power to the module as either 3.3v or 5v, and the onboard regulation will safely put out 3.3v to power the LCD panel itself. The signal lines will already be at 3.3v. All comms between your STM board and the LCD panel will be at 3.3v natively.
The LCD panel uses an NT35510 LCD driver IC, so you just poke data at it, and it will handle the timing of signal comms to the LCD panel itself, saving you the grind of bit-banging the data to the LCD with correct timing etc. This is a 3.3v logic level part. casually 'chatting' to it (signal) at 5v will most likely damage it.
The PCB provided in the LCD Module doesn't do anything to ensure the signal wires are 3.3v logic level, only the power, ie to turn the backlight on, and to power the NT35510 driver IC. It's your own problem to ensure the signal wires are 3.3v logic level. Of course being aimed at 3.3v MCUs this is not a consideration of the manufacturer.
I'm using this with an Arduino Due (should it ever arrive!) so I'm also good at 3.3v, but since I have to make a PCB to essentially adapt the module to the Arduino form factor, I felt I should probably make it useful to boards with either 3.3v or 5v logic level. Of course this is also limited to the formfactor of the Mega2560 or the Due, as that's the formfactor I am using. I don't really want to design a shield for something I don't have, also I'm pretty sure that the Arduino Mega/Mega2560 would be the only 5v boards with enough IO pins to run this 16-bit parallel interface, so it's probably unnecessary to make a formfactor for anything else.
Tooki got it right. My purpose here was to essentially adapt the LCD module 'built-in shield for 3.3v logic level STM boards' to the Arduino via my own custom 'gender bender' STM formfactor<->Adruino board formfactor with logic level shifting to make it useful to both 3.3v and 5v boards. The 5v/3.3v ability of the LCD module stated in the 'specs' is ONLY for POWER, not SIGNAL. I need to level-shift the SIGNAL because I plan for this to be compatible with 5v logic level Arduino MCU boards.
I have read these pages over and over a number of times, because I purchased them from a country where English is not the primary language. I always read them with a level of scepticism, and look for non-obvious information which may be omitted due to the assumption by the manufacturer/publisher that you already know it, or that it is irrelevant to their product as they sell it. If you buy it for some other purpose, you're on your own. That and endless rabbit-hole type research into the supposed purpose it was sold for, and you start to get a clearer picture of how it will or won't work for your own project.
This topic was all about how to use the IOREF pin on (most) Arduino boards to ensure that 3.3v native signals go through un molested, and 5v signals go through after being shifted down.
That said, it looks like I'll be running the TXS0108E chip, and running the LCD side on 3.0v, as the NT35510 can work down to much lower than even that, AND VCCa MUST be lower than VCCb, so if VCCb is coming in at 3.3v, I MUST have VCCa at a lower level. I figured -0.3v would be enough of a difference.
tifkat