[A83] Re: 83p os
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[A83] Re: 83p os
On Mon, 14 Apr 2003 20:33:03 -0500
"Jeff" <telepath75@hotmail.com> wrote:
> 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
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...
> 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
>
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.
> 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!
>
> Jeff
>
--
Max Sikstrom
pengi@molik.org
MoLiK programming and demo group
http://www.molik.org/
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