Re: FPGA for PCI based servo control board

[John Sheahan <jrsheahan-at-optushome.com.au>]

On Tue, Apr 01, 2003 at 09:07:52PM -0500, John & Beth Kasunich wrote:
> fact that the question was PCI related, but I was responding to
> the fact that you seemed to consider PCI compatibility the sole
> criterion for choosing the FPGA.

que?  My only point here was 5V pci can be driven with a 3v3 
rail.  

personally - I'm still of the opinion a PCI interface is 
inappropriate for  motor control. I think this should be 
outside the PC and use something fast and serial to communicate with it.  
but thats just my opinion - with the particular constraints I have.

> 
> It sure is.  I design VFDs and other industrial equipment.  ALL
> of our stuff runs on 5V, even the newest designs.  We are using
> some very recent Hitachi micros with built in PWM generators, 
> A/Ds, and so on, and they are 5V parts.  Regardless of where
> the PC world goes, 5V is still the universal standard in the 
> industrial world, and I see no reason to change that.

my recent designs has been partly fast comms - 1.5V core in 
virtexII pro (with limited 3V3 and decent 2v5 IO) 
and partly 5v logic doing random stuff.
comms is not 5v. Its fast becoming not 3v3 any more. 

for me - I'd be choosing modern fpgas that fit and route 
well - with flexible io pinout - and are cheap. 
which means low voltage core today.  The older stuff is just horrible
by comparison. 

Just spent 2 days juggling RTL to partition a design into available 
PLCC84 devices. ended up with XC95108's.  Bad choice, pinout cannot be
maintained when its full and the design tweaks.

I usually interface to higher voltage/current (ie the outside world) 
with discrete tansistors - so  fpga IOvoltage  is not really an 
issue here. And since all the logic is inside the fpga - there -is- 
nothing else to interface to.

for a hobby project - the package is really more of an issue. 
I dislike soldering pin pitch less than ~0.8mm by hand, which 
is a much bigger restriction on device choices today.
john

> 
> John Kasunich
>