[A83] Re: 83p os
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[A83] Re: 83p os
On Tue, 15 Apr 2003 13:25:14 +0200 (MEST)
robvanwijk@gmx.net wrote:
>
> He was probably referring to the fact there is no boot that executed every
> time you turn the calc on. The "boot" you mention is more like
> initilization.
>
Well... I called it boot, because TI calls it boot in there manuals...
>
> Before you're gonna put a whole lot of effort in this, you should be aware
> that (under US laws) there currently is no known method to distribute non-
> TI OSes legally. Your name sounds scandinavian, so those specific laws
> might not apply to you, but please, be careful before you do something
> that might get you into trouble.
>
I'm from sweden, but I'm not planning to distribute the OS... I just write if for fun. I don't think there will be any applications for the OS, It is just a test to use the TI multitasked...
> When a new OS is loaded, this is what happens:
> Control is given to the boot page (1F on the 83+, 7F on the 83+SE), which
> clears the other pages used by the OS. Then the new OS is received and
> written to Flash rom. When the entire OS has been stored to Flash, a check
> is performed to verify the authenticity of the OS. If this check is
> succesful,
> some byte(s) are altered, to reflect this. (I do not know what bytes these
> are, or what the are changed to, but that should be easy enough to check.)
> Now, whenever the calc is reset (because you reset it, or pop the batteries
> or something like that), these bytes are checked. If they are "incorrect",
> (because it isn't a TI-OS, or because it's corrupted), the boot page kicks
> in, and all you can do is load a new OS.
> The trick in loading your own OS is this: make sure that in your OS file,
> these bytes already have the right value. Then, when the OS loader is
> verifying it, pop the batteries. That way, the next time you start it, it
> sees
> these bytes have the correct values and will assume it's valid.
>
cool hack... thanks...
>
> Good luck,
> Rob van Wijk
>
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>
--
Max Sikstrom
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MoLiK programming and demo group
http://www.molik.org/
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