[Coco] Coco proto board

[jdaggett at gate.net]

Mark

I know that a CPLD is very flexible but changing it from some points of view 
requires learning how to write the HDL language and then use the software 
to burn the CPLD. Using discrete logic and/or CPLD in conjunction with user 
selectable addressing may offer more acceptance. 

Correct a 44 pin CPLD just does not offer enough pinouts. A 80pin QFP 
might be a better alternative. 

james
On 15 Sep 2007 at 10:21, Mark McDougall wrote:

> jdaggett at gate.net wrote:
> 
> > This was discussed a while back and the community then was split
> > between using discrete logic versus CPLD for address decoding. A
> > part of the community sees a CPLD as fixed address range and
> > somewhat inflexible. 
> 
> The idea of using a CPLD is so the decoding *isn't* fixed!
> 
> I was thinking of offering a few standard options, such as 16/32KB
> ROM, various I/O decoded at $FF40-FF5F.
> 
> Right now I was looking at a 44-pin device, but that leaves very
> little - perhaps too little - options IMHO. After routing data, 8-bit
> GPIO bus, CTS#, SCS#, NMI#, R/W# plus a ROM_CS# & READ#, there's only
> a few pins left over for *internal* address decoding and _no_ external
> address decoding (no generation of ext CS lines)...
> 
> I'll have to think more about this...
> 
> Regards,
> 
> -- 
> |              Mark McDougall                | "Electrical Engineers
> do it |  <http://members.iinet.net.au/~msmcdoug>   |   with less
> resistance!"
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