[A83] Re: 83p os
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[A83] Re: 83p os
Depending on how its configured, all that would need to be done is IM 2
after the romcall. Unless, of course, the user is accessing flash in the
TI-OS, then am interrupt-resident program would be disabled.
> problem with writing this sort of os for the 83+ is that you'd can't write
> to flash without calling a romcall and these romcalls switch to im 1.
>
> brandon sterner
> > I had this idea once, but wasn't ambitious enough.
> >
> > The TI-83 doesn't exactly have a "boot." However, the TI-OS uses the
z80
> > interrupt mode 1 (IM 1) in handling interrupt routines. This indicates
> that
> > upon an interrupt, the calc should call code at $0038. However, $0038
is
> in
> > ROM, and cannot be manipulated! Interrupt mode 2, though, can be
> configured
> > to handle interrupts nearly anywhere in memory. What you need to do is:
> > -disable interrupts
> > -set interrupt mode 2
> > -set the I register to the most significant byte of a page-aligned 257
> > byte
> > buffer
> > -fill the 257-byte buffer with the same byte, referring to an address
> with
> > the same byte in each significant place (for example, $9393 or
$9494)
> > -install interrupt code at the specified address (for example, $9393
or
> > $9494), starting with EXX / EX AF,AF' and ending with EX AF,AF' /
EXX
> /
> > RETI
> > -enable interrupts
> >
> > That is a quick overview of interrupts. What do you mean by the TI-OS
> > files? I recommend reading intguide.txt (focused on TI-83+, remember)
and
> > asmhelp.zip, found on ticalc.org, to learn about interrupts and the VAT
> > (variable allocation table). If you have any specific questions feel
free
> > to ask!
> > > Hi...
> > >
> > > I'm going to write a mutitasked os to my ti83p. Does anybody know how
> > > the ti-os files are stored and what addresses are called on
> > > boot/interrupt?
> > >
> > > TIA
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