[Coco] Dual UART with FIFO Card for the CoCo

[Phill Harvey-Smith]

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.

Cheers.

Phill.

-- 
Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric !

"You can twist perceptions, but reality won't budge" -- Rush.