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Thread
2004-03-14 by LightYearCS
Ladies and Gentlemen:
This is a rumor I heard. Even a field engineer thinks he heard of this also.
It’s said that if you use the same values for each of the capacitors used in the crystal oscillator circuit that sometimes the oscillator will not start up and remain in a state of lockup. Has anyone else heard of this?
Oh, and by the way, how many SPI devices do you think the ATmega64 can handle, hrm?? J
Barry
2004-03-14 by samperi@ampertronics.com.au
At 06:39 PM 13/03/04 -0800, you wrote:
> Oh, and by the way, how many SPI devices do
>you think the ATmega64 can handle, hrm??
Well you did say you could work it out but were being lazy :-)
So if each pin can source and sink ~20mA and each input
has an input current of less than 1 micro amp, then I would
guess that it would be many, many devices (20,000??) is that
enough?? :-))
Regards
John Samperi
******************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495 Fax (02) 9674-8745
Email: samperi@ampertronics.com.au
Website http://ampertronics.com.au
* Electronic Design * Technical Services * Contract Assembly
******************************************************2004-03-14 by LightYearCS
YES!! Oh yes I love it when I can get other people to do my work :) *sigh* I'm so stinking happy now. Thanks :) Of course I will double check this information. Anyone heard about this lockup thing? Is it a malicious rumor? Barry
-----Original Message-----
From: samperi@ampertronics.com.au [mailto:samperi@ampertronics.com.au]
Sent: Saturday, March 13, 2004 6:44 PM
Subject: Re: [AVR-Chat] Oscillator Lock?!?!
At 06:39 PM 13/03/04 -0800, you wrote:
> Oh, and by the way, how many SPI devices do
>you think the ATmega64 can handle, hrm??
Well you did say you could work it out but were being lazy :-)
So if each pin can source and sink ~20mA and each input
has an input current of less than 1 micro amp, then I would
guess that it would be many, many devices (20,000??) is that
enough?? :-))
Regards
John Samperi
******************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495 Fax (02) 9674-8745
Email: samperi@ampertronics.com.au
Website http://ampertronics.com.au
* Electronic Design * Technical Services * Contract Assembly
******************************************************
Yahoo! Groups Links2004-03-14 by David VanHorn
At 06:39 PM 3/13/2004 -0800, LightYearCS wrote: >Ladies and Gentlemen: > > > > This is a rumor I heard. Even a field engineer thinks he heard of this also. > > > > It s said that if you use the same values for each of the capacitors used in the crystal oscillator circuit that sometimes the oscillator will not start up and remain in a state of lockup. Has anyone else heard of this? Post hoc fallacy. If it doesn't start, it's not because the caps are equal.
2004-03-14 by Kathy Quinlan
-----Original Message-----
From: LightYearCS [mailto:lightyearcs@zippnet.net]
Sent: Sunday, 14 March 2004 10:39 AM
To: AVR-chat@yahoogroups.com
Subject: [AVR-Chat] Oscillator Lock?!?!
Ladies and Gentlemen:
This is a rumor I heard. Even a field engineer thinks he
heard of this also.
It’s said that if you use the same values for each of the
capacitors used in the crystal oscillator circuit that sometimes the
oscillator will not start up and remain in a state of lockup. Has
anyone else heard of this?
ROFLMAO ok the only time the 2 caps are not equal is when you are tuning
the crystal (look at some old 1802 cpu designs, this was common) BUT 99%
of designs these days use EQUAL caps, when caps are needed (some uC's eg
the AT43USB355E does not have external caps as they are internal to the
uC)
I think someone is talking rubbish.
Regards,
Kat.
---
Outgoing mail is certified Virus Free.
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-----Original Message-----
From: LightYearCS [mailto:lightyearcs@zippnet.net]Thanks for putting this behind me. I didn't think it was a problem. I
Sent: 14 March 2004 09:27
To: AVR-Chat@yahoogroups.com
Subject: RE: [AVR-Chat] Oscillator Lock?!?!
only heard this from one person and a Atmel field engineer who thought
he heard it.
I'll probably ask in a couple other forums just to make sure.
Barry
-----Original Message-----
From: Kathy Quinlan [mailto:kat-yahoo@kaqelectronics.dyndns.org]
Sent: Sunday, March 14, 2004 12:32 AM
Subject: RE: [AVR-Chat] Oscillator Lock?!?!
-----Original Message-----
From: LightYearCS [mailto:lightyearcs@zippnet.net]
Sent: Sunday, 14 March 2004 10:39 AM
Subject: [AVR-Chat] Oscillator Lock?!?!
Ladies and Gentlemen:
This is a rumor I heard. Even a field engineer thinks he
heard of this also.
It's said that if you use the same values for each of the
capacitors used in the crystal oscillator circuit that sometimes the
oscillator will not start up and remain in a state of lockup. Has
anyone else heard of this?
ROFLMAO ok the only time the 2 caps are not equal is when you are tuning
the crystal (look at some old 1802 cpu designs, this was common) BUT 99%
of designs these days use EQUAL caps, when caps are needed (some uC's eg
the AT43USB355E does not have external caps as they are internal to the
uC)
I think someone is talking rubbish.
Regards,
Kat.
2004-03-14 by LightYearCS
Thanks for putting this behind me. I didn't think it was a problem. I only heard this from one person and a Atmel field engineer who thought he heard it. I'll probably ask in a couple other forums just to make sure. Barry
-----Original Message-----
From: Kathy Quinlan [mailto:kat-yahoo@kaqelectronics.dyndns.org]
Sent: Sunday, March 14, 2004 12:32 AM
Subject: RE: [AVR-Chat] Oscillator Lock?!?!
-----Original Message-----
From: LightYearCS [mailto:lightyearcs@zippnet.net]
Sent: Sunday, 14 March 2004 10:39 AM
Subject: [AVR-Chat] Oscillator Lock?!?!
Ladies and Gentlemen:
This is a rumor I heard. Even a field engineer thinks he
heard of this also.
It's said that if you use the same values for each of the
capacitors used in the crystal oscillator circuit that sometimes the
oscillator will not start up and remain in a state of lockup. Has
anyone else heard of this?
ROFLMAO ok the only time the 2 caps are not equal is when you are tuning
the crystal (look at some old 1802 cpu designs, this was common) BUT 99%
of designs these days use EQUAL caps, when caps are needed (some uC's eg
the AT43USB355E does not have external caps as they are internal to the
uC)
I think someone is talking rubbish.
Regards,
Kat.
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.618 / Virus Database: 397 - Release Date: 9/03/2004
Yahoo! Groups Links2004-03-14 by David VanHorn
At 09:46 AM 3/14/2004 +0000, Brian Fairchild wrote: >They are not equal on the STK300 and there is no reason they should be equal. Sorry, that's wrong. The two caps absolutely should be equal, unless you have a good reason for them not to be. The two caps are in series, from the crystal's point of view, and in parallel with the parasitics on the board. The formulae from the various crystal manufacturers to determine the crystal cap values all reflect this, and they all result in equal values. Even when you are tuning the crystal to a specific frequency, your goal is to arrive at equal values, but being a few pF off balance isn't as important as having the crystal on frequency, in those applications.
2004-03-14 by John Johnson
Not to split hairs here, but the two caps will never be equal. Regards, JJ On Saturday, Mar 13, 2004, at 21:39 US/Eastern, LightYearCS wrote: > Ladies and Gentlemen: > > > > This is a rumor I heard. Even a field engineer thinks he > heard of this also. > > > > It’s said that if you use the same values for each of the > capacitors used in the crystal oscillator circuit that sometimes the > oscillator will not start up and remain in a state of lockup. Has > anyone else heard of this? > > > > Oh, and by the way, how many SPI devices do you think the > ATmega64 can handle, hrm??J > > > > Barry > > > > <image.tiff>
> > Yahoo! Groups Links > > • To visit your group on the web, go to: > http://groups.yahoo.com/group/AVR-Chat/ > > • To unsubscribe from this group, send an email to: > AVR-Chat-unsubscribe@yahoogroups.com > > • Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service. >
2004-03-14 by David VanHorn
At 08:38 AM 3/14/2004 -0500, John Johnson wrote: >Not to split hairs here, but the two caps will never be equal. I think you're very much splitting hairs. Look at the crystal manufacturer's data sheets, and tell me where they show unequal values in any normal application. Or are you making the case, that like two resistors, they may be 0.001% off no matter how carefully they match them?
2004-03-14 by John Johnson
On Sunday, Mar 14, 2004, at 08:45 US/Eastern, David VanHorn wrote: > At 08:38 AM 3/14/2004 -0500, John Johnson wrote: > >> Not to split hairs here, but the two caps will never be equal. > Or are you making the case, that like two resistors, they may be > 0.001% off no matter how carefully they match them? Yes. I was implying that if the two caps have to be unequal for oscillation to start, it will always start. Regards, JJ
2004-03-14 by David VanHorn
At 08:51 AM 3/14/2004 -0500, John Johnson wrote: >On Sunday, Mar 14, 2004, at 08:45 US/Eastern, David VanHorn wrote: > >> At 08:38 AM 3/14/2004 -0500, John Johnson wrote: >> >>> Not to split hairs here, but the two caps will never be equal. >> Or are you making the case, that like two resistors, they may be >> 0.001% off no matter how carefully they match them? > >Yes. I was implying that if the two caps have to be unequal for >oscillation to start, it will always start. They do NOT have to be unequal. Where does that idea come from? In order to have oscillation, you need only these things: Gain > 1.0 Phase shift at frequency of interest, 180 degrees. and a closed loop.
2004-03-15 by samperi@ampertronics.com.au
At 08:38 AM 14/03/04 -0500, you wrote:
>Not to split hairs here, but the two caps will never be equal.
Precisely! And then there will be some caps that will be" more equal
than others"...just like humans :-))
Regards
John Samperi
******************************************************
Ampertronics Pty. Ltd.
11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA
Tel. (02) 9674-6495 Fax (02) 9674-8745
Email: samperi@ampertronics.com.au
Website http://ampertronics.com.au
* Electronic Design * Technical Services * Contract Assembly
******************************************************