[A89] Re: AMS 2.05 upgrade problem
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[A89] Re: AMS 2.05 upgrade problem
At 08:27 2002-01-16, you wrote:
>I have a question. What if ALL the 2 MB Flash rom+256 KBram on the 89 is
>cleared. How do you get a new OS on it then? I mean, there isn't any
>software on the calc anymore to install a new OS in the Flash rom. Is the
>calculator useless then?
To clear _all_ flash, you have to hack the protection. It is _very_
improbable that it would happen with a crash, and tricky even if you know
the secrets (which only a few people know). Or hardware hack the calc to
bypass the protection.
Even with bypassed protection, it isn't as easy as writing to ram to write
to flash, you have to send special commands to it.
You don't clear all then either, since the first 64K containing the
bootloader is permanently write protected and can't be cleared.
As far as I know, the bootloader does though check some bytes in the area
that could be cleared with all this hassle, and halts if they are wrong, so
if this byte(s) are cleared, then the calc would indeed be useless.
(the bootloader is this nifty thing displaying "press I to install new os"
if the the flashrom is wrong)
Unless you desolder the flashchip and program it in an external device, and
then solder it back.
///Olle
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