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Crystal Oscillator Question

I have seen several schematics like this one:

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that do not specify which pins of the crystal oscillator I should be connecting to. I know I should connect the crystal to OSC1\IN and OSC2\OUT of a PIC microcontroller. I also understand the principle behind the external capacitors, but I have not found any explanation of how to connect the crystal, only this generic two pins symbol. Which two pins are they? An explanation of where each of these pins goes would be greatly appreciated.

The crystal I have has four pins:

1 - NC or tristate enable 7 - GND/case 8 - Output 14 - Vdd(+5V)

The enable pin can be left floating or tied to +5V on this particular XO (Mouser part# 815 ACO 4 EK)

Reply to
sinner
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A crystal is a different thing to a crystal oscillator.

A crystal has only two pins that are interchangeable.

You have an oscillator module. It has a crystal and circuitry.

Attach +5V to Vdd, 0V to GND, connect Output to OSCIN.

Make sure you select the right oscillator mode (probably external high speed) when programming the PIC.

HTH

cheers, Rich.

Reply to
Rich Walker

That's because what you have is a canned oscillator and not a crystal. Feed it +5 & ground, get a (more or less) square wave at the output.

Often, a microcontroller can use an oscillator (or other clock source) instead of a crystal if the clock is fed to the xTAL1 (or equivalent) pin. Sometimes it's also necessary or desirable to set a fuse to tell the device what type its clock source is.

Canned oscillators are handy if multiple devices need to run from the same clock. They're also simpler to set up than crystals are (no caps needed) so I frequently (no pun intended...) use one when breadboarding.

Reply to
Rich Webb

The device you have isn't a crystal. It is a packaged oscillator. It almost certainly contains a crystal, but it also contains much more. Check to see if the PIC you are using can be configured for an external oscillator. If it can, use the connection instructions associated with that. The two capacitors that the standard circuits use will be useless in your case. Pin 8 has the clock signal. The rest of them don't connect to the PIC (although Vdd and GND must be connected to their respective power lines, which will also be connected to the PIC).

Reply to
Police Box

You have a canned oscillator. Connect it to OSC1/IN Set the pic up for external oscillator. Make sure you have a low impedance connection between the oscillator's ground pin, and the pic's ground pin(s) otherwise you could be radiating a lot of RF noise.

For using crystals (two pin device), get a copy of the crystal's data sheet, and go here:

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Reply to
Dave VanHorn

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