Re: gEDA-user: Question for DJ about his alarm clock

[John Doty <jpd@xxxxxxxxx>]

On Aug 15, 2008, at 5:19 PM, DJ Delorie wrote:

>
>> You're right. I'm always amused by the "noise on ground" notion. It's
>> the sound of one hand clapping. Noise relative to what?
>
> The power plane?  That board has two planes (power and ground).

Yes. But that would require no resistor between PVSS and ground to fix.

> Why
> is one always the reference?

Because that simplifies network theory. But the problem here is that  
the network theory approximation doesn't work: you have to consider  
your interconnections as transmission lines. It's 200 picoseconds  
past the rising clock edge: do you know where your return current is?

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




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