Hello!
I need to do a ipoint routine, but I've a problem with the port $11: I menage to write on the lcd, but not to read.
Example:

Code:

I thought this display "239", but i read "0"
Do anyone know why this?
Thanks you!
PS: Sorry for my bad English, but I'm French

So, you're setting column $30-$20=16 (which is only valid in 6-bit mode), then row $80-$80=0, then setting that pixel block to $EF. You then set the accumulator to $FF (for some reason0 and read in the data on the screen and display it. The biggest problem I notice is that If you want to deal with the pixel block at the top-left of the screen, you need column $20 (which is the first column block), not $30. If you're in 8-bit mode, $30 isn't even a valid column. Am I correct in thinking that this doesn't make a pixel appear on the screen?

Hum... in first, i thought than the column start at $20, but it isn't write: when i take $20, the pixel don't appear, and when i use $30, it appear... Maybe it's different in a 83+ (i use a ti82stats.fr with wabbitemu to test this)

I'm basing the numbers I'm quoting you on this documentation:

http://wikiti.brandonw.net/index.php?title=83Plus:Ports:10
http://wikiti.brandonw.net/index.php?title=83Plus:Ports:11

Yes, I've gone here to learn how to use the port $10, but it can't be that:
$2E-20 +1 = 15
96/8 = 12 = $3B - $30 +1
96/6 = 16 = $3F - $30 +1
So, there is a problem if its between $20 and $3F...
And with $30, pixels appear at the top-left of the screen

EDIT:
Solved: someone tells me i need to do a "dummy read" before, because the coordinates are update after the first "in", when we read.
Thanks you for your answer

Fascinating; I should update WikiTI if I can verify that on a TI-83 Plus calculator. That's a rather important mistake if it is indeed one. Oddly enough, my FastCopy routines in Doors CS set the column to $20 for the upper-left, and everything works well.

It's strange:
I've done some test:

Code:

It works, the screen is black
I don't understand

EDIT:
I think we can start at $20 or at $30, it's not important, the 2 are working

Maybe $20-$2F and $30-$3F are duplicates of each other in 8-bit mode. Anyway, as you say, that's not the point of what you're asking. Let's go back to your original question, which is why you can't read the LCD properly. Does anything change if you use $20 instead of $30 in the read portion of your program?

Someone found my problem: it's because when i put the coordinates, the writing is properly, but if we want to read, we have to read 2 times, because the first time, we read at the late coordinates!
Thanks for your help!

PS: I can use $20, or $30, nothing change

Aha, that's an excellent point. I didn't think of that, and I should have. Anyway, may I ask what project this is for?

It's for a project with the linkport (a kind of snake for 2 players). I had a problem with ipoint, witch put on the interrupts, and the interrupts do some problem with the port 0

Then it sounds like you were using Getkey_, which is a very bad idea. Have you considered using direct input?

Ho... _Getkey was just for the example . In my game, i use the direct imput of course

Oh, that's good! Out of curiosity, though, why are you not using something like iGetPixel to write to the gbuf, then iFastCopy to copy the graph buffer all at once?