Re: Termination of Bussed signals (CompactPCI)

[mellitz@eagle.ColumbiaSC.NCR.COM]

On Aug 4,  5:33pm, Andy Ingraham wrote:
> Subject: Re: Termination of Bussed signals  (CompactPCI)
> > Although this is not directly PCI, it is related (please let me
> > know if I should post this elsewhere)
> 
> This maillist is almost strictly PCI, not CompactPCI.  Does the PICMG
> have resources for handling such queries?
> 
> 
> > The CompactPCI spec calls for 10 ohm series termination resistors on all the
> > bussed PCI signals.  I assume the value of 10 was chosen based on an 8-slot
> > CompactPCI backplane.
> >
> > We are designing a CompactPCI target device that will be in a CompactPCI 
> > backplane with only two slots.  Does this mean we should use another 
> > value besides 10 ohms?  Thanks.
> 
> In general, you can't know in advance whether the backplane you plug
> a card into has one slot or eight.  I don't see how they could expect
> you to tailor the value of the resistor to the number of slots.
> 
> Standard CompactPCI cards with 10 ohm resistors have to work in the
> 2-slot backplane, right?
> 
> If the spec says 10 ohms, I'd say stick with 10 ohms.  Unless it says
> something different.
> 
> (But I've never seen the CompactPCI spec.)

What's this? Does Compact have their own PCI Spec? The rules for PCI (4.4.3 ff) 
state that you get 1.5" (2.0" on 64 bit systems) to your PCI chip on a 
PCI plugin card.  The spec also states that you can not attach any discrete 
devices to the PCI signals on the cards.

Regard,
Rich Mellitz, NCR
> 
> Regards,
> Andy Ingraham
> 
>-- End of excerpt from Andy Ingraham

Þˆu