what i dont get is that they continue to update the 84 se but they havent updated the 83 plus in over a year.

i kinda wish they would.

anyways i have no 84 so this poses no problem other than the fact that i dont want to die laughing when someone with an 84 se accidently enters restricted mode and starts to cry because he (or she) doesnt know how to fix it.

for that reason i hope this gets a bypass. it will help my school considerably and save many tears.

They're not going to update the 83+. It's obsolete. They only sell it as a cheap alternative.

I agree with the person who says that the TI-83 Series graphing calculators is obseolute (sp?, sorry). The same way goes with the standard TI-89: they're no longer doing OS updates, either. So, you might as well forego (sp?) with either the TI-84 Series, TI-89 Titanium, or the Voyage 200 (they did updates last time to 3.10), but not the TI-92 series.

Ultra_64

Your first spelling question is spelled "obsolete", but the second is correct with "forego".

Oh, and thanks.

Not necessarily, the TI-83+ is a cheap alternative, but it still has all the features needed for a common high school student. Not everyone wants to spend that extra money for a USB Port and extra Archive.

Well, I'm in middle school, and I have an 84+ se and an 89T. I don't know how to use 1/2 of the features of the 84+se. Heck, I don't even know what a sine wave is! The main reason I purcahsed an 89T is because you can program in C for them, which makes it much easier for me to program in Asm. (Pkease don't respond to this post explaining to me what sine and tanget and cosine and all that junk is!)

Same here, I was required to have an 83+ or 84+ for highschool but I got an 89T for Programming C :-)

*ignores your comment*

It's a wavey thing, sort of like an ocean wave.

If that's true, how come TI released 1.19? (See link)

actually nvmd. they updated the 83 plus after the 84 plus update to 1.19

WOOHOOO WOOHOO WOOHOO!!!!!!

Why couldn't someone just rewrite the addresses in memory that control the lock feature? Give it the same visual result, but still allow things? I do not know much, but it seems plausable to me.

-W-

Because very few people know how to crack the Flash Protection to do this. It would also have many risks involved, such as your batteries dying when the patch is run or something.

How exactly is the Flash protected? If it's something with hardware (a certain port that controls it), it might be possible to stick some probes on the pins of the chip and look at what's going on with a logic analyzer, but then again, it's all so small that it might be hard.

Disabling the Flash Protection is pretty much done with software. But I dont know if it would help you figure out how to disable it. The very few people that know how to do it on both the z80 and 68k won't tell and for good reasons as well.

But I dont know if it would help you figure out how to disable it. => But I dont know if it would help you figuring out how to disable the flash protection with electronic devices.

Well, unlocking flash is easy. You just output 1 to port 14h. However, this must be done from certain OS pages, and also with some extra code before it (see linked page.)

Certainly could work. I did some investigation last night and I believe I've found the approximate location of the lockdown routine:

In section
:020000020017E5

around line
:2048A000

I changed the first few bytes of the line mentioned above, from
:2048A00005DE3E20CD133

to
:2048A00005DE333C30038

33C30038 are the 8 bytes changed. Essentially, INC SP and JP $0038 are performed in place of JP PO, $0CD1 and INC SP
The result is that the lockdown screen is shown briefly and then routine exits to the home screen, adding some stuff to the text shadow and the home screen; some memory is taken up, but you can get it right back by pressing [CLEAR] one or more times.

Unfortunately, it doesn't appear to be as simple a matter of changing those bytes. TI-Connect says that the format is invalid when I attempted to send the modified to my calc. However, it works just fine in TiLEm...

Two problems:

1) If you make changes, make sure you update the checksums at the end of each line, or else your file will be an invalid format.

2) OS files have a digital signature; changing them will invalidate this signature and will prevent them from being send to a calculator (unless you exploit a flaw like the OS validation flaw in the 83+/83+ SE calcs)

So, how exactly is the checksum calculated?

But I haven't changed the digital signature just by changing one line, have I?

I believe checksum on the end of each line is calculated by finding the two's compliment of the sum of each of the bytes. So: add up all the bytes (mod 256) and then, calculate 256 - <sum>. You might want to check the docs on the Intel Hex format to be sure (since that's all it is)

And regarding the digital signature: you invalidate it by changing just one bit. This is how digital signatures work. Your only hope here is either (1) use a flaw in validation, (2) modify the 8xu in such a way that the combination of all your modifications will in fact require the same digital signature, or (3) crack TI's private key. Note that either (2) or (3) would probably require brute forcing by a rather large cluster of computers, so I'd recommend (1), which might not be possible if TI didn't screw up on the 84+ (whether they did or didn't I don't know.)

Or solution (4), which would be to unlock flash and do it that way...

Thanks for the info on the checksum. I haven't yet tried to send the modified OS to my calc yet, but I'll keep everyone posted on how it goes.

I think each file also has a checksum in the last 2 bytes (the whole .8x* file, different than the ones at the end of each line). To quote from a file format document: The checkum is the sum of all bytes starting at the var header (0x0B). Offset 0Bh is where the file comment starts, IIRC.