Re: Crystal circuits

I am using the Atmel at90s2313 8 bit microcontroller.

http://www.atmel.com/dyn/resources/prod_documents/DOC0839.PDF

----- Original Message -----
From: "Marc Alexander" <marcwolf123@yahoo.com>
To: <vectorlist@vectorlist.org>
Sent: Monday, October 20, 2003 11:24 PM
Subject: Re: VECTOR: Crystal circuits

>
> Just to follow up, I did a search for a document that can explain the
detail
> better than me, here it is:
>
http://www.saronix.com/Document_Files/AppNote-BasicOscillatorDesign-0305.pdf
>
> The Pierce type is more common (at least until many recent extra low power
MCU's)
> and is more immune to noise, drives a higher frequency and does consume
> a bit more power than Colpitts.
>
> The Colpitts type is usually used where very low oscillator power
consumption
> is needed (standby small battery powered devices) and is less noise
> immune and more sensitive to oscillator component values, and can't
> drive as high a frequency as Pierce.
>
> Your MCU data book should have some details on example crystal hookup and
> parts selection.
> Some MCU's actually have software selection between Pierce and Colpitts
modes,
> but I don't think yours does (what MCU is is again?)
>
> Cheers,
>
> Marc
>
> ----- Original Message -----
> From: David Shoemaker
> To: vectorlist@vectorlist.org
> Sent: Tuesday, October 21, 2003 3:43 PM
> Subject: VECTOR: Crystal circuits
>
>
> While building up the two beta 9100 keyboard wedge boards I realized I
didn't have any 22pf caps. So I tossed a pair of 100pf caps
> onto my breadboard of the circuit and everything worked great.
>
> Then I went to build the perfboard version and realized I only had two of
the 100pf caps and as I wanted to leave the breadboard
> version intact for now so I grabbed a pair of .1uf caps.
>
> Hooked everything up and it didn't work.
>
> So I checked everything twice more and still no go. Got to wondering if
maybe the value of those caps is really important and
> realized I have NO idea how to spec them nor even what they do.
>
> So can anyone enlighten me?
>
> I have seen circuits use 18pf, 22pf and 27pf for the crystal caps. The
100pfs do work, but I wonder now if I just got lucky.
>
> David
>
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Received on Tue Oct 21 12:30:10 2003