Re: A83: Patching the Ti83+ ROM?
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Re: A83: Patching the Ti83+ ROM?
I vaguely remembered someone mentioning that TI's protection device will
block writes to the flash chip if it isn't in an unlocked state, that's why
I said that. Of course, it may just be a figment of my imagination.
Actually, the TI-83 Plus is newer than the TI-89 (at least in terms of when
it was announced). The TI-89 was announced with the TI-73 on March 13th,
1998. The TI-83 Plus was announced on January 11th, 1999. Quite a few
things could have happened in that gap.
Port 14h is what is used to unlock the flash. Outputting a value of one
(from a "special" page, perhaps after a series of strange code execution)
will unlock. This will cause the usually read-protected page of 1Eh to be
unprotected, and will allow writes to flash (using an equally complicated
procedure). A value of 0 to port 14h will lock the flash again. Port 16h
is used somewhere along the line too, but I haven't looked closely enough to
see what that is.
As for the flash chip, it's an AMD manufactured AM29F400B. The docs for it
should be available from AMD's website, if not, I can upload the .pdf
somewhere. It's a 512K chip, and has a minimum of 1,000,000 program/erase
cycles per sector according to AMD (as opposed to the 100,000 figure TI
quotes).
There is no page like yours for the TI-83 Plus. I have researched and
compiled tons of information (about everything, not just the flash), which I
have repeatedly offered to give out to anyone who wants to compile it in
some sort of organized fashion (so far only Henk Poley with his Romcall
reference). The problem is that it's completely disorganized and scattered
between my computer, my TI-92 Plus, five notebooks, and my brain.
-Dan Englender
----- Original Message -----
> I don't think all that should be nessesairy. you probably only have to
pull
> that write enable low, as hyperbyte said.
> In the ti89 it is just one pin you need to lift, and put a switch there.
> (it has to be connected at boot, or the boot will fail)
> I find it unprobable that the designers att TI did it much more
complicated
> on the 83+ then on the 89. (specially considering that the 83+ is older
> then the 89, isn't it? or maybe I remember wrong on this one...)
> That port 14h, is it only for "unlocking" or is it used for controlling
the
> flash further? has anyone checked what flash chip there is in the 83+, and
> found the specs for it?
> Hm.. I feel that I really know nothing about the 83+...
> if it is for controlling, probably you need some special cycles on the
bus,
> similar to on the 89 before you are allowed to write to it. maybe with
> correct delays (the nops). that would be a real pain...
> probably true if it is only for unlocking too actually.
> Isn't there a page like mine (http://alh.dhs.org/ti89/) but about the 83+?
> that would rule :)
> I really feel like I want to start fiddling with the 83+ now.. anyone has
> one to donate? :)
>
> ///Olle
>
>
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