What is output of quartz crystal across MCU

Papabravo

Joined Feb 24, 2006
17,003
So if we dont connect any probe, since it effects the meausrement and distort the signal by loading.
What exactly is shape of signal at XTIN & XTOUT of MCU when a crystal is connected acrss it with each pin having capacitor to GND?

Is it sine, square, distorted sine?
It depends on the resonant frequency of the the crystal and the properties of the amplifier inside the processor. What the processor, a digital device, will "see" is a signal with two states and short transitions between the stares at a periodic rate. There is not much else to say about the waveform that could be considered useful.
 

MisterBill2

Joined Jan 23, 2018
9,493
Bringing in the probe tip close to the connection may pick up enough signal to observe the waveform. Usually, in a digital oscillator, the crystal drive is some sort of pulse waveform, close to a square wave, while the signal back to the input is closer to a sine wave. IF the circuit is not going into saturation because of excess feedback.
 

MrChips

Joined Oct 2, 2009
24,431
So if we dont connect any probe, since it effects the meausrement and distort the signal by loading.
What exactly is shape of signal at XTIN & XTOUT of MCU when a crystal is connected acrss it with each pin having capacitor to GND?

Is it sine, square, distorted sine?
Why do you need to know the shape of the signal?
 
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