[Coco] Coco proto board
msmcdoug at iinet.net.au
Fri Sep 14 20:21:01 EDT 2007
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...
| Mark McDougall | "Electrical Engineers do it
| <http://members.iinet.net.au/~msmcdoug> | with less resistance!"
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