Searching \ for '[PIC]: Crystal recommendation?' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/devices.htm?key=pic
Search entire site for: 'Crystal recommendation?'.

Exact match. Not showing close matches.
PICList Thread
'[PIC]: Crystal recommendation?'
2000\12\06@160350 by Dave Bell

flavicon
face
Looking for a reference for 20 MHz crystal for a 16F(873/877)-20.
I assume it will be in HS mode, and need (TBD pF) parallel caps?
Something easy to locate would be nice! :{) Digikey, say?

Dave

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email spam_OUTlistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body


2000\12\06@181336 by Bob Ammerman

picon face
I am using Digikey part number 300-6042-ND 20MHz crystal with 16F876, no
problems. This is in an HC49/US case (does US standard for ultrashort?), a
nice small package.

US$0.88 each

I am using them with 3x 39pF caps (but I didn't really check to see if that
was right). The signal looks like  a nice clean 5V sine on my scope.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email .....listservKILLspamspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body


2000\12\06@184822 by Bob Ammerman

picon face
----- Original Message -----
From: Bob Ammerman <RAMMERMANspamKILLspamPRODIGY.NET>
To: <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU>
Sent: Wednesday, December 06, 2000 6:05 PM
Subject: Re: [PIC]: Crystal recommendation?


> I am using Digikey part number 300-6042-ND 20MHz crystal with 16F876, no
> problems. This is in an HC49/US case (does US standard for ultrashort?), a
> nice small package.
>
> US$0.88 each
>
> I am using them with 3x 39pF caps (but I didn't really check to see if
that
> was right). The signal looks like  a nice clean 5V sine on my scope.

er... I mean 2x 39pF caps (now where would I put that third cap?)

{Quote hidden}

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listservspamspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body


2000\12\06@185021 by Thomas C. Sefranek

face picon face
Dave Bell wrote:

> Looking for a reference for 20 MHz crystal for a 16F(873/877)-20.
> I assume it will be in HS mode, and need (TBD pF) parallel caps?
> Something easy to locate would be nice! :{) Digikey, say?
>
> Dave
>
> --
> http://www.piclist.com#nomail Going offline? Don't AutoReply us!
> email @spam@listservKILLspamspammitvma.mit.edu with SET PICList DIGEST in the body

I have to say you are probably better served buying the complete
oscillator from Digi-key.
I just got 10 of them (20 Mhz.) at $2.50 each. No muss, no fuss, they
just work.
Small package, (4 pins in an 8 pin dip), and low power.

--
 *
 |  __O    Thomas C. Sefranek  KILLspamtcsKILLspamspamcmcorp.com
 |_-\<,_   Amateur Radio Operator: WA1RHP
 (*)/ (*)  Bicycle mobile on 145.41, 448.625 MHz

ARRL Instructor, Technical Specialist, VE Contact.
hamradio.cmcorp.com/inventory/Inventory.html
http://www.harvardrepeater.org

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email RemoveMElistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body


2000\12\07@085215 by Olin Lathrop

face picon face
> I have to say you are probably better served buying the complete
> oscillator from Digi-key.
> I just got 10 of them (20 Mhz.) at $2.50 each. No muss, no fuss, they
> just work.
> Small package, (4 pins in an 8 pin dip), and low power.

That can be a convenience for a low volume product, but will cost at least
double what the crystal and two caps cost.  One good reason for having an
external oscillator is if you are driving multiple devices from the same
clock.

I've never had any problem with having the PIC drive a crystal directly
(except the time I didn't cover the window on a 16C77/JW), and I think of
this as the "easy" solution.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, spamBeGoneolinspamBeGonespamembedinc.com, http://www.embedinc.com

--
http://www.piclist.com hint: To leave the PICList
TakeThisOuTpiclist-unsubscribe-requestEraseMEspamspam_OUTmitvma.mit.edu


2000\12\07@091900 by Fred Bailey

flavicon
face
I agree that the crystal and two 33 pf caps usually works very well at 20MHz.
The only trick to remember in troubleshooting is that when you probe with the
oscilloscope probe, use the X10 (times 10) impedance instead of the X1. Using
the X1 setting will stop the oscillation when the scope probe makes contact.
This gives the impression that the crystal is bad when it is not.

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestspamTakeThisOuTmitvma.mit.edu


2000\12\07@104020 by Andrew Kunz

flavicon
face
One of the ways we made things adjustable with RF equipment we were working on
was to connect OSC1 to a logic gate (inverter), and subtract it's input
capacitance from the cap that's normally there.  You can then attach a probe to
the output of the logic gate, which is now isolated quite well from the
oscillations of the micro.

Now that Fairchild et al have single logic gates available in SOT-23 form, it is
very easy to justify the addition of the pads for the gate.

C1 = C2 - C of logic gate

If you need to tune the frequency, make the one cap a varcap

o-----|>o--- Test Point
|
o--------------------OSC1
|
o-----|X|------o-----OSC2
|              |
|              |
- C1         C2-
-              _
|              |
|              |
GND           GND










Fred Bailey <baile_fEraseMEspam.....TDIPOWER.COM> on 12/07/2000 09:10:26 AM

Please respond to pic microcontroller discussion list <EraseMEPICLISTspamMITVMA.MIT.EDU>








To:      RemoveMEPICLISTEraseMEspamEraseMEMITVMA.MIT.EDU

cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: Re: [PIC]: Crystal recommendation?








I agree that the crystal and two 33 pf caps usually works very well at 20MHz.
The only trick to remember in troubleshooting is that when you probe with the
oscilloscope probe, use the X10 (times 10) impedance instead of the X1. Using
the X1 setting will stop the oscillation when the scope probe makes contact.
This gives the impression that the crystal is bad when it is not.

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestspam_OUTspamKILLspammitvma.mit.edu

--
http://www.piclist.com hint: To leave the PICList
RemoveMEpiclist-unsubscribe-requestTakeThisOuTspamspammitvma.mit.edu


2000\12\07@113604 by David VanHorn

flavicon
face
At 09:10 AM 12/7/00 -0500, you wrote:
>I agree that the crystal and two 33 pf caps usually works very well at 20MHz.
>The only trick to remember in troubleshooting is that when you probe with the
>oscilloscope probe, use the X10 (times 10) impedance instead of the X1. Using
>the X1 setting will stop the oscillation when the scope probe makes contact.
>This gives the impression that the crystal is bad when it is not.


Probe the crystal case.
This will not give full output voltage, but it will also not stop the osc,
and will barely affect frequency.

Otherwise, the handy shortwave radio works really well.

--
Where's dave? http://www.findu.com/cgi-bin/find.cgi?kc6ete-9

--
http://www.piclist.com hint: To leave the PICList
EraseMEpiclist-unsubscribe-requestspamspamspamBeGonemitvma.mit.edu


2000\12\07@115823 by Harold M Hallikainen

picon face
On Thu, 7 Dec 2000 08:34:48 -0500 Olin Lathrop
<RemoveMEolin_piclistKILLspamspamEMBEDINC.COM> writes:
{Quote hidden}

       And we're getting ceramic resonators with built-in capacitors for
something like 50 cents each. The cost savings over an external
oscillator or even over a crystal and a couple capacitors is substantial.
Also, there's a substantial savings in board space since the resonator
with capacitors is in a 3 pin SIP (or even smaller when surface mounted).
       muRata has a nice search engine where you can put in a processor number
and it will come back with resonator part numbers that have been
characterised for that processor. It's at
http://www.murata.co.jp/search/ic-e.html .


Harold



FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:
dl.http://www.juno.com/get/tagj.

--
http://www.piclist.com hint: To leave the PICList
piclist-unsubscribe-requestSTOPspamspamspam_OUTmitvma.mit.edu


2000\12\07@120659 by Harold M Hallikainen

picon face
       I've generally been able to probe the output side of the PIC oscillator
with a 10x scope probe with no problem. Probing the input side kills it
right away. When I'm doing "crash and burn" debugging for a chip for
which I have no emulator, this is generally the first thing I check on
the dead prototype. It obviously won't do anything without a live
oscillator!
       In a previous post I mentioned how great ceramic resonators are. We've
replaced crystals completely with resonators. I'm now working on a very
small product that is all SMT using the PIC 16F627 running at 4 MHz. I'd
generally found that at 4 MHz, pretty much anybody's resonator with caps
would work. At 16 MHz, only the muRata would work reliably. On this
latest project, I tried the only SMT resonator Digikey had (Panasonic, I
think). It would not reliably work with the 16F627, so now I'm "surface
mounting" a SIP resonator from them.

Harold


On Thu, 7 Dec 2000 11:34:26 -0500 David VanHorn <spamBeGonedvanhornSTOPspamspamEraseMECEDAR.NET>
writes:
{Quote hidden}

FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today!  For your FREE software, visit:
dl.http://www.juno.com/get/tagj.

--
http://www.piclist.com hint: To leave the PICList
EraseMEpiclist-unsubscribe-requestspamEraseMEmitvma.mit.edu


2000\12\07@123530 by Simon Nield
flavicon
face
assuming you don't need the extreme accuracy of a crystal then I would have to agree with harold and
go for a surface mount ceramic resonator with built in capacitors from murata . i have a load
different boards with the 20MHz part fitted and they all work fine.

one nice thing about resonators that's worth remembering is that they start up about 10 times faster
than a crystal. not a great help for pic circuits as they have a start up delay anyway, but can be
useful elsewhere.

small, cheap and they also look cool... oh dear, time to get a life.

regards,
Simon

--
http://www.piclist.com hint: To leave the PICList
@spam@piclist-unsubscribe-request@spam@spamspam_OUTmitvma.mit.edu


2000\12\07@133927 by Stephen B Webb

flavicon
face
> one nice thing about resonators that's worth remembering is that they start
up about 10 times faster
> than a crystal. not a great help for pic circuits as they have a start up
delay anyway, but can be
> useful elsewhere.


I seem to remember reading in one of the PIC datasheets that you can turn
the startup delay off.  What exactly happens when it's off, but
your clock isn't ready for prime time yet?  Could you just put in a dozen
or so nop instructions right after the wakeup to compensate?  Or do "bad
things" happen with a whacky clock?

-Steve

--
http://www.piclist.com hint: To leave the PICList
spamBeGonepiclist-unsubscribe-requestspamKILLspammitvma.mit.edu


2000\12\07@175956 by Olin Lathrop

face picon face
> I seem to remember reading in one of the PIC datasheets that you can turn
> the startup delay off.

I didn't look this up explicitly just now, but I remember there are two
separate startup delays.  There is a delay from the time Vcc gets above a
threshold, which can be at least partially disabled on some PICs.  For
crystal oscillator mode (which also applies to ceramic resonators), there is
an additional 1024 cycle delay to make sure the oscillator has stabalized.
I don't think this delay can be disabled.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, .....olinspam_OUTspamembedinc.com, http://www.embedinc.com

--
http://www.piclist.com hint: To leave the PICList
TakeThisOuTpiclist-unsubscribe-request.....spamTakeThisOuTmitvma.mit.edu


More... (looser matching)
- Last day of these posts
- In 2000 , 2001 only
- Today
- New search...