[SI-LIST] Re: Virtex -5 PCI ibis file and simulation
- From: crr1231@xxxxxxx
- To: Aubrey_Sparkman@xxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 08 Jul 2008 20:22:58 -0400
I am using PCI (33MHz). The simulator says that my problem is with undershoot
but I'm thinking that the model isn't very good. It is a point to point trace
and very short (PPC to V5). I don't have room on the board for series resistors
and don't realy want to go down that path. I'm dissapointed that the simulator
(ICX) and the ibs model for the V5 is showing what it does. The only way I can
reduce the undershoot is to insert the V5 with a fast-6mA driver in place of
the PPC IO. Any other suggestions are welcomed.
Thanks,
Charlene
-----Original Message-----
From: Aubrey_Sparkman@xxxxxxxx
To: weirsi@xxxxxxxxxx; crr1231@xxxxxxx
Cc: si-list@xxxxxxxxxxxxx; cradtke@xxxxxxxxxxxxxxx
Sent: Tue, 8 Jul 2008 1:13 pm
Subject: [SI-LIST] Re: Virtex -5 PCI ibis file and simulation
Charlene,
You didn't say whether you were using PCI or PCI-X, but my memory says
both PCI and PCI-X specs allowed HUGE amounts of over and undershoot.
PCI-66 was often the worst case. Are you sure you violate the *shoot
specs? The spec allows so much, I've only ever seen this once.
Steve is right that series resistors can reduce the *shoots but that
takes a lot of resistors and they can kill your setup time if you have a
long link or several loads.
Aubrey Sparkman=20
Enterprise Engineering Signal Integrity Team=20
Dell, Inc.=20
Aubrey_Sparkman@xxxxxxxx=20
(512) 723-3592=20
"The single biggest problem in communication is the illusion that it has
taken place." -- George Bernard Shaw
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of steve weir
Sent: Tuesday, July 08, 2008 2:42 PM
To: crr1231@xxxxxxx
Cc: si-list@xxxxxxxxxxxxx; cradtke@xxxxxxxxxxxxxxx
Subject: [SI-LIST] Re: Virtex -5 PCI ibis file and simulation
PCI is so old that this could be a real problem. I don't believe Xilinx
does anything to particularly slow down V5 outputs when set for PCI I/O.
External resistors should take care of the problem.
Steve.
crr1231@xxxxxxx wrote:
> I was wondering if anyone else in the community has been able to
implement (in simulation and in Hardware) PCI at 3.3v on the virtex 5
device (point to point between processer and FPGA). It seems that the V5
model that I am using responds the same whether I use 3.3V or 3.0V and
gives the same over and undershoot regardless of trace length using the
PCI models in the ibis file. According to my questionable simulations,
overshoot is within range but undershoot is out by 300mV. My concern is
that the sim is somewhat accurate, in hardware - the input diodes will
not be able to clamp and the device will be damaged (over time). If
anyone has successfully used an ibis model ( I am using the 1136
package), would you mind emailing it to me?
> With much appreciation,
> Charlene
>
>
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