Re: Termination of Bussed signals (CompactPCI)

[Andy Ingraham <ingraham@wrksys.ENET.dec.com>]

> 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.)

Regards,
Andy Ingraham
×\J