FreeLists / si-list / [SI-LIST] Re: PCI Rise/Fall Time

[<Aubrey_Sparkman@xxxxxxxx>]

Kenny,
Are the clocks monotonic and in spec?  How much less than 1 are your
slew rates? =20

Jim is probably right.

Slower (closer to 4) slew rates are easier to get ringing under control,
but Faster slew rates (closer to 1) are better from a jitter perspective
- not very relevant for PCI-33.
IF slew rate is the only spec that are you failing and none of your
devices are slots, the question I would ask is:  Can anyone give me a
reason to even try to slow down the slow rate and fix?


Aubrey Sparkman=20
Enterprise Engineering Signal Integrity Team
Dell, Inc.=20
Aubrey_Sparkman@xxxxxxxx=20
(512) 723-3592

The Greatest Pleasure in Life is Doing what People say can't be done...

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Peterson, James F (EHCOE)
Sent: Thursday, February 15, 2007 5:59 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: PCI Rise/Fall Time

Kenny,

The PCI standard specifies a test load for measuring the slew rates. It
does not include the 33 ohm series resistor, so you'll be ok. (I think
it's still 1k Pullup, 1K Pulldown, and a 10pf pulldown....)

Jim Peterson
Honeywell

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Kenny Frohlich
Sent: Thursday, February 15, 2007 12:29 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] PCI Rise/Fall Time

Hi All,
  I have a design that has a 33MHz PCI bus.  There are one master (CPU)
and five PCI devices on the bus and these devices are connected in a
daisy-chain topology.  There's a serial termination of 33 Ohms at the
beginning of the bus and an end termination of 3K at the end of the bus.
The setup and hold times of this PCI bus in my design are within the
spec.; however, the rise and fall times (slew rates) are not.  The rates
are too slow (less than 1) compared to the spec (1 to 4).  Changing the
value of the serial termination to O Ohm helps a little, but it still
does not meet the spec. =3D20
  =3D20
  Can you help me fix this issue?
  =3D20
  Thanks,
  Kenny
  =3D20
=3D20
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