Calculator Community > ASM
Unlocking Flash
Geekboy1011:
its true and it is confusing
he is amazing i believe unlocking the flash allows 1 users to read write and run any thing to or from the flash
it allows modifications to most of the flash weather it is already used or not
(for stuff like the defrag fix ) it allows acces to patch the os and there are a few more things but that is what i can remember :)
DJ Omnimaga:
you can even listen to music without usb drive. www.revsoft.org got a program called RealSound to do that. It takes a lot of memory, though, for like 30 seconds of music
3.1415926535:
haha, this is crazy stuff. i can't even begin to imagine how it works. I kind of want to figure out now
BrandonW:
TI restricts writing to Flash and reading from the certificate through a locking/unlocking mechanism. To unlock Flash, a special sequence of z80 instructions must be executed from a "privileged page", meaning an area of Flash memory granted unlock access through hardware. It is impossible to change which pages are privileged.
The privileged pages are 1Ch/3Ch/7Ch, 1Dh/3Dh/7Dh, 1Fh/3Fh/7Fh, 2Fh/6Fh (84+ and 84+SE only), and presumably 1Eh/3Eh/7Eh. All of these pages are either OS pages, permanently write-locked boot code pages, or the certificate (non-code pages). Because TI's code is on these pages, we cannot unlock Flash.
Code could be added to the privileged pages to unlock Flash for you, but to write it, you must first unlock Flash. :)
The only way to do it is to trick the OS or boot code into unlocking it for you, and there are various exploits available to do that. TI does not like this, because it allows you to write to the user archive (potentially destabilizing it), modify or replace the OS, modify or replace the certificate, etc.
Over the years, we've learned a lot about how the calculator works and found stable exploits that either cannot or are unlikely to be patched or fixed by TI, so this isn't as scary as it used to be.
DJ Omnimaga:
I get confused when it comes to that technical stuff, but would this involve anything related to cracking the OS signing keys? To me TI are shooting themselves in the feet with that stupid DMCA thing. That, combined with how tighly locked-down the TI-Nspire is and how limited devellopement on that platform is, it's becoming clear TI are doing everything to prevent any further calculator devellopement involving gaming.
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