[SI-LIST] Re: PCIX and Open Drain Output drivers
- From: "Ingraham, Andrew" <Andrew.Ingraham@xxxxxxxxxx>
- To: "si-list" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 15 Feb 2002 09:21:48 -0500
> I've got a question about reflections caused on the net by using an =
open
> drain configuration. What I'm doing is I'm taking a PCIX driver, =
grounding
> the Logic input and toggling the Tristate input. My concern is the =
output
> impedance differential for different logic levels. Should be very =
high for
> "1's" and very low for "0's" . Is this a major source of concern on
> PCI/PCIX nets since we are talking about reflected wave switching?
.
The fact that it is different should not matter.
The falling edge is like any other PCI/PCI-X transfer. The rising edge =
is a passive pull-up and somewhat slow. It is probably close to an =
exponential waveform (RC-limited).
In all cases I am aware of, the rising edge is an asynchronous transfer =
(if not for both edges). The rising edge is not reflected wave =
switching.
Andy
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