[Coco] [Color Computer] USB Anyone?
dragon at aurigae.demon.co.uk
Sat Apr 16 12:51:44 EDT 2005
> Beware that the MC2 bit of $FF90 Init0 register controls where the SCS
> line is decoded from teh GIME chip. MC2 low then the SCS is decoded
> from $FF50 to $FF5F. MC2 high will decode $FF40 to $FF4F.
This is of course different from the way the CoCo 1,2 and Dragons select
it which is IIRC from $FF40-$FF5F.
> Beisdes most PLD chips are $0.75 to $1.25. The IDE interface that is
> functional equivalent to the Glennside IDE takes only 26 macrocells of
> a 9572 series CPLD. IT won't fit into a 9536 do to the lack of pinouts.
Would be interested in seeing the HDL code for that.
> I still contend that one large CPLD device will beable to shrink the
> board size significantly such that teh savings in board costs will
> overide any extrra cost in the CPLD. It is a trade off.
A CPLD also has the major advantage, thta if you get the logic wrong on
the first design (and in my experience of such things you almost
cirtainly won't get it completely correct first time), you can mostly
change it by changing the VHDL/Verilog that you program into the CPLD,
which saves you having to cut tracks, and rewire.
Another things to considder is that using a CPLD does not nesescrally
mean using surface mount, as for example the 9536, 9572 and 95103 are
alll available in PLCC, which is somewhat easier to work with. I have
done surface mount and whilst is's not a difficult to do as I initially
thought, PLCC/DIP is definatly easier :)
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