[Coco] Dual UART with FIFO Card for the CoCo

Sun Jun 13 19:25:40 EDT 2010

Gene,
If the Duart Pack is used in a multi-pak, and the disk controller placed in 
a different slot, it wouldn't interfere with the RTC inside of the disk 
controller. Since I used the SCS* signal, the duart pak would only be active 
when it's slot has scs* directed to it. Any pack that doesn't need 
$FF50-$FF5F could still be plugged into the duart packs feedthru connector.

I will probably do another design using a quad uart chip and I can allow 
alternate mapping schemes such as the $FF1x or $FF3x area which is available 
on the CoCo3 (but not on the CoCo 1 or 2). If I do a quad pack, I will 
probably map them into 16 bytes and include a "switch" so that you switch in 
the first set of 2 or the second set of 2 uarts. I would probably also 
include a SR latch for each of the four UARTS such that when one of them 
generates an IRQ* it sets it's corresponding latch - the four latch bits 
will have an input port so that, if needed, the coco could decide which of 
the four uarts generated the IRQ*. These are just some ideas. I suppose I 
could actually map all four UARTS into the same 8 bytes with a "switch" to 
select which of the foure uarts occupies the memory space... these are just 
some thoughts, but if you think it's worth looking into, I'll go to work on 
it. I am having fun with all of this :-)
Since my Doctor has yet to clear me to go back to work, designing this stuff 
keeps me from going bonkers.

----JOHN

----- Original Message ----- 
From: "Gene Heskett" <gene.heskett at gmail.com>
To: <coco at maltedmedia.com>
Sent: Sunday, June 13, 2010 6:09 PM
Subject: Re: [Coco] Dual UART with FIFO Card for the CoCo

> On Sunday 13 June 2010, sales at gimechip.com wrote:
>>Gene,
>>I mapped the UARTS at $FF50-$FF5F - I split SCS* in half and passed
>>$FF40-$FF4F out to a feed-thru cartridge connector for the disk controller
>>to plug into and I used $FF5x for the two UARTS.
>
> Mmmm, that I think will interfere with the real time clock chips in many 
> of
> our disk controllers.  Most of them are in the $FF50-5F range by way of
> additional decoding in the controller.  Some are a bit portable, iirc I 
> can
> put the clock in my TC^3 controller in the high block of $FF7x by jumpers.
> The various other scsi/ide drive interfaces do something similar, but I
> should defer to Mark Marlette and GCCC for fresh definitions on that as I
> don't have that hardware.
>
> One thing that rather fell by the wayside was that at one point Tandy 
> tried
> to set std addresses for this and that, then didn't stick to it at all 
> well,
> probably because there were quickly more aftermarket devices than they
> imagined there would be.
>
> In any event, this has been a PIMA for me for 20 some years, and I have 
> more
> than once run through my 5 minute monolog of swear words directed at Tandy
> because Tandy didn't fully decode their own crap.  Friggin bean counters
> will be the death of the engineering profession yet. :(
>
>>I need to go look at the Datasheets - you've got me wondering if I
>>overlooked something - I think the 16550 only needs 8 addresses, but I
>>better check... just checked - yep just 8 addresses...
>>whew :-)
>>
>>-John
>>
>>
>>----- Original Message -----
>>From: "Gene Heskett" <gene.heskett at gmail.com>
>>To: <coco at maltedmedia.com>
>>Sent: Sunday, June 13, 2010 5:37 PM
>>Subject: Re: [Coco] Dual UART with FIFO Card for the CoCo
>>
>>> On Sunday 13 June 2010, sales at gimechip.com wrote:
>>>>On CoCo3.com, I asked for project ideas and requests. One request was
>>>> for a Dual UART card w/FIFO. I thought this would be a good one, so I
>>>> spent yesterday studying the datasheets and then, this morning I
>>>> created a preliminary design using E.A.G.L.E. The complete project is
>>>> now posted here:
>>>> http://www.coco3.com/community/2010/06/a-dual-uart-with-fifo-card-for-t
>>>>he -coco Let me know if you spot any potential problems with the design.
>>>> Thanks - John
>>>
>>> The only problem I see is the additional i/o addresses it needs.  8 per
>>> chip
>>> sure beats the original 16450's 16 per chip, but with the coco's very
>>> limited I/o mapping, at least in os9, finding that space is going to be
>>> fun.
>>>
>>> In my own situation, I do have a dual port ACIA, addressed adjacent to
>>> each
>>> other from FF64 to FF6B (iirc), which meant I had to hack Rogers BT pack
>>> to
>>> use FF60-63.
>>>
>>> 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 looked at that myself but about 2 decades ago, so any ideas I may have
>>> had
>>> then are moot now.  And I of course am not the least bit allergic to
>>> plugging in my iron and fixing it as long as I can adequately see what
>>> I'm doing.  Diabetes is trying to fix that for me now.  But, I'm still a
>>> C.E.T.,
>>> so I'd be willing to be a test site, I have more than 1 coco3 here.
>>>
>>>
>>> --
>>> Coco mailing list
>>> Coco at maltedmedia.com
>>> http://five.pairlist.net/mailman/listinfo/coco
>>
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>>
>>
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>>
>>--
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>>
>
>
> -- 
> 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)
> Don't look now, but the man in the moon is laughing at you.
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco

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