[Coco] CocoFlash Updates

Gene Heskett gheskett at shentel.net
Sun Sep 18 22:44:19 EDT 2016

On Sunday 18 September 2016 16:01:20 Darren A wrote:

> On Sun, Sep 18, 2016 at 5:03 AM, Gene Heskett wrote:
> > I have lamented for at least 25 years because someone hasn't made a
> > one chip addin board for the coco itself, restricting the address
> > space used by the PIA's to the 4 byte wide access they need, which
> > would free up 7, 4 byte wide addresses from $FF04-FF1F, and 7 more 4
> > byte wide blocks from $FF24-FF3F. Thats 14 more 4 byte wide devices
> > we could address in those two spaces.
> If a device wants to use the ghosted PIA addresses it can do so
> without any need to modify the CoCo. Asserting the SLENB* pin on the
> cartridge port disables the internal '138.

Any timing issues?

> Unfortunately, the CoCo ROMs do use the ghosted addresses from
> FF1C-FF1F during initialization, so that area should probably be
> avoided.

One 4 byte block lost there.

> Additionally, if you want to be compatible with the Dragon, 
> avoid using FF04-FF07 as that range is used for the internal 6551 ACIA
> on the Dragon 64.

And another there, still leaves 12 slots.

> One thing I don't know is if the CoCo 3 GIME responds to any of the
> ghosted addresses of FF22 for its shadowing of the old 6847 VDG
> control lines.

I wasn't aware it did that.  Testible somehow?

> - Darren

Thanks Darren.

Cheers, Gene Heskett
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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