Cap+Crystal values?

[scarr]

Hi,
I am working with the PIC16F876 I am having some stability problems. the chips appears to fail to run sometimes or crash!! I have isolated this dowm to the crystal + caps combination.


Can anyone advise the best combination for max stability:

Best CAP type & value
Best crystals 20Mhz type

Thanks
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This message was ported from CCS's old forum
Original Post ID: 125

[Steve H.]

You should use a fundamental (as opposed to harmonic), parallel mode crystal. This crystal will have a specified load capacitance value (Usually 20 pF). This is the value you should use with the crystal. Also be sure to set the fuses to HS or High Speed. The crystal must be mounted right on the oscillator pins and the capacitors must be mounted right on the crystal with the other end right on the ground plane. If you don't have a ground plane, run a wide trace from the capacitors directly to the nearest ground pin.

Intel has an excellent application note on crystals, etc. Search their site for crystal or oscillator, etc.

Places like Digi-Key have excellent selections of crystals...

Steve H.
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This message was ported from CCS's old forum
Original Post ID: 131

[Dean Lopez]

:=Hi,
:=I am working with the PIC16F876 I am having some stability problems. the chips appears to fail to run sometimes or crash!! I have isolated this dowm to the crystal + caps combination.
:=
:=
:=Can anyone advise the best combination for max stability:
:=
:=Best CAP type & value
:=Best crystals 20Mhz type
:=
:=Thanks


I've found best results from using precision oscillators that have the crystal and capacitor already inside them.

Dean
___________________________
This message was ported from CCS's old forum
Original Post ID: 133

[Steve H.]

:=I've found best results from using precision oscillators that have the crystal and capacitor already inside them.
:=
:=Dean

That's an excellent suggestion! These ALWAYS oscillate :-)

Steve H.
___________________________
This message was ported from CCS's old forum
Original Post ID: 136