Re: Universal Card

[reynoldst@mobilian.com (Todd Reynolds)]

Mr. Grbic,
I am currently using a 3.3V card in a universal slot successfully. Part of 
the role of a universal board socket is to allow the use of both 5V Only 
and 3.3V Only cards.

My design uses the 5.0V and the 3.3V supplies but is set-up as a 3.3V only 
card with the Vi/o pins being 3.3V based on the motherboard detecting the 
3.3V card and using 3.3V for the Vi/o pins.

What you want to do is design a 3.3V only card(3.3V Keyed Only!) since that 
is your I/O requirement.

If you wanted to be able to use your card in both 3.3V and 5.0V motherboard 
sockets, then you would need to get an FPGA that could handle both or get a 
very good/fast level translator/buffer. The second is not recommended and 
not allowed by the specifications but if it is a prototype or test board 
you may be able to get away with it but it will be very difficult and you 
will spend a large amount of time designing it - unless you can find a chip 
that someone has already designed to do the translation for you (Maybe a 
universal Bridge Chip?). I have never tried it but there should be others 
on this list with more experience in this area.

FYI: You are never supposed to add components to the signal lines. They 
should be point-to-point connections though the specification allows stubs 
within tolerances.

-Todd

At 09:02 AM 9/6/2002, you wrote:
> 
>
>  Dear PCI 
> experts, 
>
> 
>
>  The electrical spec (Pci rev 2.2) recommend that PCI components on a 
> universal board must use dual voltage I/O buffers, powered from
>  "I/O" designated power 
> pins. 
>
> 
>
>  In  my  PCI  universal card I'm using a PLD (FPGA device) which is 
> powered by 3,3V supply and can not drive and be driven by 3.3V or
>  5.0V 
> devices. 
>
> 
>
>  Any comments about this 
> matter? 
>
> 
>
>  Now my question is: in a new universal board can I leave unused 
> dedicated Vi/o pins on the PCI edge connector (properly decoupled to
>  the  ground  plane)  and  use only the 3.3V supply from the PCI 
> connector (or 5V supply with a regulator) to power up the PLD? Also,
>  regarding  I  am  using  PCI edga universal connector, and not dedicated 
> 3.3V PCI connector, do I have to add some serial resistance
>  onto the signal lines to compensate for the clamping 
> diodes. 
>
> 
>
>  Thanks for any 
> suggestions. 
>
> 
>
>  Goran 
> Grbic 
>
>  Senior H/W Apps 
> Engineer 
>
>  MOSAID 
> Technologies 
>
>  p: 
> 613-599-9539/1481 
>
>  f: 
> 613-591-8148 
>
> 
>