On Tue, 21 Jul 1998, Al Kossow wrote:
> > I can try to partition things, but I think I'd wind up with just
> > 2 smaller PLDs each needing 70 IOs, which doesn't really help anything.
>
>
> I'm puzzled why you need all the I/O. There is a pattern generator on the
> adr/data lines, and signature analyzer, and the rest is a 6502 micro. Were
> you implementing the keyboard/LED display in there too?
>
You need ADDR in from the 6502 (16 bits) DATA in from the
6502 (8 bits) ADDR out (16 bits) and DATA out (8 bits) That's
48 already, plus there are other miscellaneous control signals.
I said 70 just to be conservative. It's probably more like 60.
As far as I know, no PLD has IO macrocells. They can be
configured as inputs or outputs. I looked into this for the
MACH stuff and that looks to definitely be the case. I don't know
if some other family lets you configure pins to be true IOs. If
there were such an animal, it would cut the number of pins required
roughly in half.
Joe
