Hi George,

Sounds like you still have some strange behavior with your project, yes?

Yeah, you have to keep the 'scope's loading effects in mind when probing the
OSC pins. In case you might need to gauge the accuracy of your crystal (say
in the future or something), you can always spit out a PWM signal via the
hardware CCP and measure that signal -- at least it will not load down the
oscillator circuit and affect the frequency (load-pulling).

If you haven't already, you might want to download the PIC18C Reference
Manual (DS39502A) from Microchip's web site. Check out section 2.10 on page
2-24. Actually, all of Section 2 is on the Oscillator.

I have not studied up on the PIC18F1220 yet, but could you give more details
about the reset circuit you are using?
Is the watchdog timer being used in your application?
If so, could it be timing-out when you think it might not be?
What are the symptoms that are causing the erratic behavior?

If you already know about all of this, I certainly do not mean to talk down
to you. Just offering some suggestions to get you on track.

Best regards,

Ken Pergola



-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of gtyler
Sent: Thursday, August 28, 2003 2:25 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC:] 18f1220 xtal osc.


You are right! After this I checked, and what is actually happening is that
when I put the scope probe on the xtal the osc stops. The real problem is
the way startup happens (I think). I am not using mclr and have enabled the
startup timer. I will not mod the design to use mclr so I can set the
startup reset time by hardware. I assumed that the erratic operation was due
to the osc.

Thanks to all that replied.
George

----- Original Message -----
From: "Ken Pergola" <no_spam@LOCALNET.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, August 26, 2003 10:23 PM
Subject: Re: [PIC:] 18f1220 xtal osc.


> Hi George,
>
> As few questions:
>
> 1) It's hard to tell from your post, but I'm curious to know what led you
to
> the conclusion that the crystal is starting erratically? (I'm not trying
to
> be a meanie here -- the answer to this question might eventually lead to
> your solution.)
>
> 2) Is the crystal definitely a parallel-cut type?
>
>
> Regards,
>
> Ken Pergola
>
>
>
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of gtyler
> Sent: Tuesday, August 26, 2003 4:15 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC:] 18f1220 xtal osc.
>
>
>  Hi all,
>             I'm looking for suggestions: I have a pic18f1220 running in
> HSPLL mode at 10 Mhz, and yes, I do need the speed. I have been unable to
> make the xtal start reliably. I found some info on uchip's web site, but
in
> spite of changing the caps to all values between 12 and 47P it still
starts
> erratically. also tried changing xtal manifacturers. Has anyone else had
> similar problems, or has some suggestions?
>
> Regards,
>             George
>
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