Re: Apple IIc plus

["mressl@gmail.com" <mressl@gmail.com>]

Now THAT is interesting :-). Once I find the time I'll check if
there's any access to C5XX.

Thanks a lot!

Marc.-

pd: I was starting to believe the 2 kB were distributed on ROM bank 2,
at $CE00-CFFF and $DE00-DFFF, but that accounts for only 1 kB of
memory, and doesn't have any sense, as the controlling logic would be
quite hard. But what you are telling me makes a lot of sense! Thnx
again!

On Aug 22, 3:28 am, mdj <mdj....@gmail.com> wrote:
> On Aug 22, 11:53 am, mdj <mdj....@gmail.com> wrote:
>
> > On Aug 21, 5:28 am, "mre...@gmail.com" <mre...@gmail.com> wrote:
>
> > > Now my questions:
> > > * Does somebody know if $CE00-$CFFF is the correct memory range?
> > > * Are there any other RAM memory areas in the $C000-$FFFF ROM address
> > > space?
> > > * Is it shared with some of the main or language card memory, or is it
> > > stand-alone memory?
> > > * Is it non-volatile RAM?
>
> > That RAM is used as a track buffer for reading and writing 3.5" disks.
> > If memory serves, it's 2KB, and was more than likely SRAM.
>
> If you don't get any other leads, I'd try this:
>
> An access to $C5xx *probably* enables the RAM chunk at $C800-$CFFF. An
> access to $CFFF would disable it.
>
> That range is the "extended firmware space" on the Apple II. A card in
> any slot is free to use it. The $CFFF protocol is the established way
> that all cards relinquish use of the space, and an access to your
> cards firmware space is the green-light to activate address decoding
> in that area. Have a look through the firmware for a dummy access to
> $CFFF - that might provide all the info you need.
>
> Cheers,
>
> Matt