[A83] Re: 83p os
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[A83] Re: 83p os
> > The TI-83 doesn't exactly have a "boot." However, the TI-OS uses the
>
> Well... The TI-83 DOES have a boot... It must have. When you start your
> calc for the first time with a new OS, the execution have to start
> somewhere...
>
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.
> Thanks, but I've used IM 2 before, but I want to code a OS so I can
> control the entire memory and also use IM 1.
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.
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.
>
> --
> Max Sikstrom
> pengi@molik.org
>
Good luck,
Rob van Wijk
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