From: Scott McDonnell (netsamurai_at_comcast.net)
Date: 2007-05-22 13:25:11
Aren't we assuming that only one cartridge at a time is being used? If
not, perhaps we should be talking about making some type of expandable
bus for the C64 using the cart port and the IRQs. While describing the
method yesterday, I was thinking how this same method could be used to
switch in and out different cartridges.
But, yes, it should be possible to decode the $DE00-$DEFF and
$DF00-$DFFF addresses even further using a bit more complex circuitry.
The full address bus is connected to the cart port and you would use the
IO1 and IO2 to get the attention of your decoding circuitry. Might even
be able to make the IO space somewhat configurable. Of course, this is a
bit complex for just a text description, I think and a CPLD would be
better suited to handle this.
Scott
> -----Original Message-----
> From: owner-cbm-hackers@ling.gu.se
> [mailto:owner-cbm-hackers@ling.gu.se] On Behalf Of Rainer Buchty
> Sent: Tuesday, May 22, 2007 7:00 AM
> To: cbm-hackers@ling.gu.se
> Subject: RE: How to design non-trivial cartridges for c-64?
>
>
> On Mon, 21 May 2007, Scott McDonnell wrote:
>
> > IO1 and IO2 are address decoded outputs. This means that if
> you read
> > or write to $DE00-DEFF (any of those locations...yeah, the address
> > decoding on the C64 is VERY wasted) [...]
>
> I'd like to add that his might be the really hard task, i.e.
> finding an
> address space which is not preoccupied by some more or less
> widely used
> peripheral.
>
> MIDI interfaces ($de04-$de07 or $de00-$de03, depending on the
> "religion"), the REU itself, IDE interface, CMD devices, cartridges
> (FC3, AR6, ...) come to my mind.
>
> Rainer
>
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>
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