[A83] Re: MirageOS remembering program location
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[A83] Re: MirageOS remembering program location
> Van: Dan Englender <dan@calc.org>
>
> > So you say that pages $09 - $15 are only used for (fixed) data storage?
> > Or has Ti some 'backdoor' which makes it possible for the ROM to
> > execute from these pages?
>
> ...Err, no, not exactly. 08h-15h (08h-69h on the SE) are used for both
> applications and user data archive. The calculator can dynamically set
> which pages it wants to allow code to run from (pages with apps on them).
> I haven't looked into detail on how this is done on the 83 Plus (though
> it has to do with ports 5 and 16h), but on the SE it has a lower bound
> (every thing below this will run), and an upper bound (everything above
> this will run) as ports 22h and 23h respectively. Apps are all loaded
> sequentially from high pages down, so whenever an app is loaded to the
> calculator, the high bound is updated to allow code to run from that
> page. These bounds can only be changed by when the flash protection is
> "unlocked", which can only be accomplished by code running from pages
> 1Ch, 1Dh, and 1Fh.
Don't you know anything about the RFSH-pin, Dan Englander? Do you know a
better way? Or are you afraid that anyone finds out? Oohw, conspiracy
theories ;-)
btw, Flash execution protection might just use the same thing as RAM
execution protection, not that it's any usefull hack, I think. This
protection is just there so nothing bogus happens when you try to run
something inside a non-existant App. Or are there any other pages that are
exec protected too?
----
Flash pages (Ti83+):
$00-$08 free exec
$09-$15 hardware dependant execution protection (Apps space)
$16-$1F free exec
$1C, $1D, $1F write to Flash
----
> > There are only 2 other RAM pages on the SE (next to the 2 normaly
> > loaded), if I'm informed well. So what do you mean? It's, or the '3rd',
> > or the '4th' RAM page that let it also crash. So "some" is a bit wierd
> > in this context I think.
>
> ...You're not informed well :) There are six other RAM pages on the SE
> (other than the normal two). That's why I said some.
Then why can this application that is able to switch between two "virtual"
Ti-83+[SE] (by switching RAM pages) only 'emulate' 2 Ti's, instead of 4?
Henk Poley <><