[SI-LIST] Re: pci driver strength
- From: "Ingraham, Andrew" <Andrew.Ingraham@xxxxxxxxxx>
- To: SI <si-list@xxxxxxxxxxxxx>
- Date: Thu, 2 Aug 2001 08:49:18 -0400
PCI drive strengths are described in the PCI Specification using V/I curves
(Figure 4-4 in the spec) and min/max limits (Table 4-4). Your drivers
should meet those requirements.
A consequence of those drive strengths is that many (but not necessarily
all) situations do depend on the reflected wave to reach nominal amplitude.
Due to the variations in drive strengths, trace impedances, and topologies,
you can get quite a bit of overshoot. The amount of overshoot is not
specified, but section 4.2.2.3 talks about overshoot tolerance of inputs and
I/Os.
Revision 2.1 of the PCI spec was replaced with Revision 2.2 more than 31
months ago.
Regards,
Andy
> ----------
> I am working on an ASIC that has a 3.3V PCI 2.1 complianace interface
> and I am doing hspice simulation on the output buffer. I understand
> PCI uses reflected wave switching, so a buffer must not be too strong.
> My question is, is there a requirement saying that if the output before
> reflection is higher than a certain voltage, the driver is too strong?
> I couldn't find it in the specification itself.
>
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