Virtex 4 package layout

Hi

I am laying out a board for a Virtex 4 FX20 in a FF672 package. Now would
it be ok if I connected some of the NC pins for this device such as ground
and VCCO so that I could use an FX40 or FX60 if I wanted? Would any damage
be done to the FX20 by connecting to these NC pins?

Thanks

Jon

Jon,

NC is just that: no connect.  We reserve the right to do anything we
might need to do with these pins, so just follow the rules: do not
connect them to anything at all.

Austin

>NC is just that: no connect.  We reserve the right to do anything we
>might need to do with these pins, so just follow the rules: do not
>connect them to anything at all.

There was a time when you could rely on a label like that...when a
door marked PRIVATE would be respected...when NC meant "NC"...when
people didn't ask WHO SAYS I CAN'T PRESS THIS BUTTON??

But hey, it's 2008.

Mike

On Feb 15, 9:09=A0am, MikeShepherd...@btinternet.com wrote:
> >NC is just that: no connect. =A0We reserve the right to do anything we
> >might need to do with these pins, so just follow the rules: do not
> >connect them to anything at all.
>
> There was a time when you could rely on a label like that...when a
> door marked PRIVATE would be respected...when NC meant "NC"...when
> people didn't ask WHO SAYS I CAN'T PRESS THIS BUTTON??
>
> But hey, it's 2008.
>
> Mike

It depends on the interpretation of NC. (Beware of the hidden meaning
of Aronyms)
Some users mistakenly think it means: Xilinx has Not Connected
anything to this pin, so I can connect anything I want to it.
The more correct meaning is: Xilinx asks you Not to Connect anything
to this pin, because it might already be used for mysterious
undocumented purposes.
This latter meaning goes back to vacuum tube (valve) sockets in the
'fourties.
Peter Alfke

>It depends on the interpretation of NC...Some users mistakenly
> think it means: Xilinx has Not Connected anything to this pin...

I'm aware of the ambiguity, but, when you use an abbreviation, it's
your job to make sure the reader knows what it means.  This is why,
when I see AFAIK, HTH, IMHO etc, I think "another who wants to talk to
the world but is too self-important to spend time writing in full".

At one time, semiconductor data sheets were superb documents,
obviously written by professional technical writers.  Now, it's clear
that they're often written by engineers who believe that "anyone can
write".

Mike

Peter Alfke wrote:
> On Feb 15, 9:09 am, MikeShepherd...@btinternet.com wrote:
>>> NC is just that: no connect. We reserve the right to do anything we
>>> might need to do with these pins, so just follow the rules: do not
>>> connect them to anything at all.
>>
>> There was a time when you could rely on a label like that...when a
>> door marked PRIVATE would be respected...when NC meant "NC"...when
>> people didn't ask WHO SAYS I CAN'T PRESS THIS BUTTON??
>>
>> But hey, it's 2008.
>>
>> Mike
>
> It depends on the interpretation of NC. (Beware of the hidden meaning
> of Aronyms)
> Some users mistakenly think it means: Xilinx has Not Connected
> anything to this pin, so I can connect anything I want to it.
> The more correct meaning is: Xilinx asks you Not to Connect anything
> to this pin, because it might already be used for mysterious
> undocumented purposes.
> This latter meaning goes back to vacuum tube (valve) sockets in the
> 'fourties.
> Peter Alfke

Austin, Peter,
Are you sure? In UG075, the V4 packaging spec., Ch1 introduction it says:-
"All of the devices supported in a particular package are pinout compatible 
and are listed in the same table (one table per package). Pins that are not 
available for the smaller devices are listed in the "No Connects" column of 
each table. "
I think this means that you can connect up unused pins so that you can 
upgrade to a bigger part should the whim take you. Unless you have a 
different idea from me of 'compatible'?
Cheers, Syms. 

Symon,

OK, I will go quiz the "experts."

Not sure, but I do not think the "common large footprint" is a
'no-brainer' (common footprint fits all) for smaller parts (plugged onto
a layout for a larger part) in V4.

Stand-by,

Austin

>Symon,
>
>OK, I will go quiz the "experts."
>
>Not sure, but I do not think the "common large footprint" is a
>'no-brainer' (common footprint fits all) for smaller parts (plugged onto
>a layout for a larger part) in V4.
>
>Stand-by,
>
>Austin
>

Austin,

Do you have any information?

Thanks

Jon

Just had a look at the ML405 board schematics and it seems to indicate that
the board can take an FX20, FX40 or FX60 device.

Jon,

OK, I was WRONG.  I am not often WRONG, but, I can be WRONG, and I have
been WRONG in the past.

NC is no connect.  We don't use those pins, and they are not connected
internally in V4, and V5.

Sorry for any confusion.

Austin