[Coco] [Color Computer] Re: New member

[James Diffendaffer]

--- In ColorComputer at yahoogroups.com, Phill Harvey-Smith <dragon at a...>
wrote:
> James Diffendaffer wrote:

> > in there but the cheapest design requires a 3.3V part and I don't know
> > how the CoCo buss will deal with that. 
> 
> You could of course use some level shifters but that of course would 
> increse component count & cost. Depends if your 3.3V part is 5V 
> tollerent, it may work, cirtainly I have interfaced a Xilinx
XC9572XL to 
> the Dragon without level shifters and that seemed to work.

It's a buffer chip that shifts levels between 3.3V and 5V lines.  It
lets one chip handle the upper byte buffering in both directions
instead of one for each direction.


> > I need to look at the Dragon connector to see if I can make it work 
> > with just jumpers.
> 
> If we are talking about the Cartrage connector, the only difference
IIRC 
> is the 12V on pins 1 & 2, but you would prolly not need them so could 
> leave them unconnected.

I didn't need 12V anyway so it should work as is.

> > so I might use an XD card rather than IDE.  XD uses a simple 8 bit
> > interface that requires less logic than IDE.
 
> MMC/SD might be worth a shot as this only uses 4 wires, might be 
> harder/easier depending on what other logic is going in there too.

MMC/SD is serial so it would require bit banging (not that again) or a
serial chip so it would be more complex software or hardware wise than XD.

> Though if XD is literally an 8 bit port that just needs decoding then
> maybe not :)

It just needs data lines and some lines for buss logic.

> > magazine.  Anyone know a good source for the AY-3-8910/12/13 chips
> > besides ripping up an old machine???
> 
> Bought a few AY-3-8912 a few months back off ebay.
> 
> Phill.

Thanks... guess I'll have to add a watch for those.





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