A86: Re: Re: new emulator
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A86: Re: Re: new emulator
Many times, TI uses port 6 as a temporary storage place.
----- Original Message -----
From: Liyang Hu <liyang@liyang.freeserve.co.uk>
To: TI-Emu ML <ti-emulator@lists.ticalc.org>; TI-86 Asm ML
<assembly-86@lists.ticalc.org>
Sent: Thursday, December 23, 1999 2:26 PM
Subject: A86: Re: new emulator
>
> hmm... thanks for prompting me to look at my code again - after messing
with
> TI86Emu for a while, I managed to find the bit of code that's messing my
> emulator up. It gets here straight after a keypress...
> Around 0x6960, ROM page 0x0a, we see this chunk of code:
>
> 6957 IN A,($06)
> 6959 PUSH AF
> 695A LD A,$80
> 695C OUT ($06),A
> 695E LD A,D
> 695F LD ($8000),A
> 6952 POP AF
>
> that's definitely writing to the ROM... (unless bit 7 of port 6 actually
> does something... I was under the impression that this bit was ignored,
ne?)
> My emu crashes at 6960, just as it attempts the write.
> I can see TI86Emu going through this bit of code as well, but it ignores
the
> write, as far as I can tell. Now, my question is: WTF is it doing writing
to
> the ROM ?!?!?!? That's just going to make my code a lot more
complicated...
> (I'm not checking whether the mem is writable or not, for speed reasons. I
> suppose I could always patch the ROM? What do you guys think?)
>
> > At what address in the ROM does it do this? Some devices will
> > use writes to
> > ROM as hardware control registers, but the calc doesn't do this.
> >
> > > Should the ROM (program) be trying to write to the ROM (memory)
> > during its
> > > execution?
>
> sayoonara!
> --
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>
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