[Coco] Dual UART with FIFO Card for the CoCo

[sales at gimechip.com]

Yes indeed :-)
I will redesign the Uart card so that the address range can be selected as 
$FF1x, $FF3x or $FF5x
That should make some folks happy :-)
-John

----- Original Message ----- 
From: "Gene Heskett" <gene.heskett at gmail.com>
To: <coco at maltedmedia.com>
Sent: Sunday, June 13, 2010 9:57 PM
Subject: Re: [Coco] Dual UART with FIFO Card for the CoCo


> On Sunday 13 June 2010, sales at gimechip.com wrote:
>>Gene,
>>In response to your following question:
>>======================================
>>"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."
>>======================================
>>RESPONSE:
>>--------------
>>The CoCo 1 and 2 wastes most of the $FF0x/$FF2x space and this waste is
>>"mirrored" with the $FF1x/$FF3x area. It wouldn't be too difficult to
>> modify the CoCo 1 and 2 so that the PIA's were not mirrored in the
>> $FF1x/$FF3x space thus freeing the $FF1x and $FF3x areas for use.
>>
>>On the CoCo 3 however, the PIA's only occupy the $FF0x and $FF2x areas.
>> The $FF1x and $FF3x areas are already available for use on the CoCo 3. In
>> fact, the Y3 select output of the 74LS138 provides a select signal that
>> is active on $FF1x/$FF3x - this select could be easily decoded further
>> for user projects.
>>
>>-John
>
> John, I'll have to plead guilty to not ever chasing through the CC3 logic 
> to
> see that.  Thank you.
>
> Stuff in the MPI generally has its own decoders, and this would open up 2
> sets of $10 wide addresses.  Whats not to like?
>
> -- 
> Cheers, Gene
> "There are four boxes to be used in defense of liberty:
> soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> People in general do not willingly read if they have anything else to
> amuse them.
> -- S. Johnson
>
> --
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> Coco at maltedmedia.com
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