[A83] Re: MirageOS remembering program location
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[A83] Re: MirageOS remembering program location
> Van: Dan Englender <dan@calc.org>
>
> > This resetting 'feature' how is it accomplished? My guess is that there
is
> > some little bit of hardware (inside or outside the Z80) that checks if:
> >
> > - the highest bit of the adress-bus is set (A0-pin?)
> > => read from / write to $8000-$FFFF
> > - the processor requests data (MREQ- or RD-pin?)
> > => we now know the Z80 is reading
> > - the R register gets an update (RFSH-pin?)
> > => gets only updated when an OP-code is requested
>
> ...Actually, it needs to be a bit more complicated because it's actually
> dependant on what page the code is actually running from, not the mapped
> address. IE. if you load RAM page 0 into 4000h, and run some code there,
> it'll still crash. The same applies for the Flash ROM execution
protection.
That means that the adress-bus part changes. But would cutting the RFSH-pin
help? That pin isn't used all (might even not be connected, but then my
theory isn't correct anyway), since Ti's don't have dynamic RAM.
And what is this Flash ROM execution protection?
> On a side note, here's a nifty quick way to "disable" the 8.8k limit on
the
> SE:
> [..]
Just put another RAM page at $CFFF-$FFFF. That definately works :-)
Henk Poley <><
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