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'[PIC]: AT-cut crystal'
2002\08\05@094049 by James.Hyslop

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Hi,

I am trying to run a PIC18C452 from an ECS HC-49US crystal
(http://www.ecsxtal.com/pdf2/hc-49us.pdf) It is a 4.000 MHz crystal and the
package says 20pF on the outside.  According to the datasheet for the PIC,
it says that a series resistor may be needed for the crystal to function
properly.  I have tried a 50K pot to vary this resistance, and I have tried
capacitor values from 18pF to 32pF and have not had any luck getting a clock
signal.  If I look at the two CLK pins on a scope, one pin has a high and
one pin has a low, no oscillation at all.  Anyone ever used this crystal
before, or have any advice on what I could try? Thanks,

James Hyslop


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2002\08\05@111642 by Olin Lathrop

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> I am trying to run a PIC18C452 from an ECS HC-49US crystal
> (http://www.ecsxtal.com/pdf2/hc-49us.pdf) It is a 4.000 MHz crystal and
the
> package says 20pF on the outside.  According to the datasheet for the PIC,
> it says that a series resistor may be needed for the crystal to function
> properly.  I have tried a 50K pot to vary this resistance,

That sounds way to high.  Start with 0 ohms and 22pF caps to ground at
either side of the crystal.  Keep the crystal close to the PIC, the leads
short, and observe good grounding techniques.  Then use the right oscillator
mode for that speed crystal.


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(978) 742-9014, http://www.embedinc.com

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2002\08\05@112336 by James.Hyslop

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If the PIC is set for RC mode, will there be a + voltage on one OSC pin and
a 0V on the other pin?  I am starting to wonder if something is wrong with
my programmer, and it's not setting the config. bits correctly.  From what
i've read, using XT or HS mode should produce a sine wave on one of the
pins, and even though I have it set for XT, I am getting the + and 0
volts...




{Original Message removed}

2002\08\05@121622 by Olin Lathrop

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> If the PIC is set for RC mode, will there be a + voltage on one OSC pin
and
> a 0V on the other pin?  I am starting to wonder if something is wrong with
> my programmer, and it's not setting the config. bits correctly.  From what
> i've read, using XT or HS mode should produce a sine wave on one of the
> pins, and even though I have it set for XT, I am getting the + and 0
> volts...

That may still be correct when it's not oscillating.


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(978) 742-9014, http://www.embedinc.com

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