[Coco] Dual UART with FIFO Card for the CoCo
afra at aurigae.demon.co.uk
Sun Jun 13 19:04:44 EDT 2010
Gene Heskett wrote:
> On Sunday 13 June 2010, sales at gimechip.com wrote:
> I would like to ask how much trouble it would be if we could figure out a
> way to isolate the first $40 of page $FF by more fully decoding the two
> PIA's it uses, so they would not see a /cs except at $FF00-03, and $FF20-23.
> That would clear out and make usable a considerable amount of i/o address
> space, allowing this to be addressed at $FF10-1F for instance. That would
> still leave room for 6 more 4 bit wide devices.
> So basically, we first need a kit that will fix all of our coco's, freeing
> up this very sorely need i/o space.
I guess as long as you always decoded from the complete address bus, you
could Assert SELNB/DSD for the address ranges $FF04-$FF1F and
$FF24-$FF3F You would of corse then need to generate an apropreate chip
select for your device, but this is all easily doable with a small CPLD
or a few LS type chips.
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !
"You can twist perceptions, but reality won't budge" -- Rush.
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