Somewhat OT: FPGA Develpment Kits
vrs at msn.com
Tue Nov 21 12:51:34 CST 2006
From: "Don North" <ak6dn at mindspring.com>
> Vincent Slyngstad wrote:
>> One of the questions I have kicking around (I even bought an XESS
>> board) was: How hard would it be to get a PDP-8 core into an FPGA
>> and arrange the pinout to correspond to the 6100 or 6120?
>> Then it wouldn't be necessary to desolder 6120's from Decmates to
>> get our SBC6120's working :-).
> Getting the logical signals to match would not be that big a deal; the
> larger problem would be getting a compatible form factor. I retargeted
> my PDP8 above to a XC2S30 and it occupies about 75% of the device. In
> a CS144 (small 0.8mm pitch BGA) one could probably make a DIP40 plugin
> carrier that was pin compatible to either the 6100 or 6120 parts.
Hmm...BGA...ick :-). We only need about 40 pins for this application.
Does anyone make a device with a smaller pincount? A nice solderable
64-pin qfp perhaps?
> None of these devices use 5V supplies, they are all 1.8V~3.3V at most.
> The power supply issue can be solved by a small linear regulator, but
> I/O level compatibility is a stickier problem.
I was thinking a 3.3v device with resistors in the input paths to keep
them within range. The outputs would probably be acceptable as-is.
> Anyway, it is an interesting problem, probably solvable given more
> thought and research. However, I suspect any low volume solution
> will still be more costly than just tracking down old IM6100 ICs
> for $10-$20. Not nearly as much fun, tho.
True, but figuring out how to one-off a replacement for a 6120 seems
a worthy project. Also, I think the cost-benefit equation will
continue to shift, as old parts get more expensive, and new ones
(hopefully) don't :-).
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