RE: Cat Box

> The problem is IOs, more than anything else. It would probably
> fit in a MACH3xx series part, but there aren't enough IOs. Off the
> top of
> my head, the CAT box needs 48 IOs for the ADDR and Data busses, plus
> another dozen or so miscellaneous signals.
>
I was going to ask that... What are your logic requirements? Is it
mostly combinatorial or clocked register stuff or do you need lots of
memory elements?

> I figure I'd need a PLD with about 70 IOs.
>
Hmmmm....

> 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.
> Schleping that many signals around a board to multiple chips will make
> the
> board more complex.
>
True. I dunno though-- a MACH211SP gives you 64 macrocells and 34
I/O's. It's incircuit programmable and only $3.70 a pop in singles.
Three of those guys are only around $12, and since you could buy larger
quantity of the same part you'd probably get in the $3.00 range pretty
quick...

> I guess I'm kind of spoiled by the Cinematronics Exorcisors,
> which
> with one chip, led to a really nice, neat, one-sided PCB design (that
> fits
> in the palm of your hand.)
>
Yep, but the board design is a one-time expense... A $20 savings in
parts cost can buy a lot of PCB.
>
> Manufacturing a board with 1 chip is certainly easier than
> manufacturing a board with many chips, so I'm not sure what you're
> getting at. Fitting something on 1 PLD trades off board complexity
> for chip complexity, which is something that I'm very willing to do.
> We'll see how it all pans out. I'm not concerned about the cost
> as much as I am the utility of the final product, since I'm not
> "manufacturing" anything on a mass scale, and I'm not doing it to
> make money. If I can get away with not needing a 2-sided PCB, then
> I've already "won" in my eyes, because, technically I could etch the
> PCBs myself if I felt like it , and save lots of $.
>
Good point. For $30 a chip I'd be inclined to just use the 435,
personally. Not like there's going to be ten-thousand people all
wanting Catbox-replacements... If the 435 was really $65 and you could
use a few 211's instead for 20% the cost I'd have to say go for the
211's.

(I've got a design at work here that's using two 22v10's instead of a
Lattice 1016 or Mach111 because the 22V10's are cheaper. You pay more
for the PCB area, and you pay more for placement and test, but the delta
is still enough to justify splitting the design...)

-Clay
Received on Tue Jul 21 11:09:59 1998