In electrical it can be equivalent to a capacitor and a resistor in parallel and then in series with a capacitor in the two-terminal network, which has two resonant points on the network, with the frequency of the concavity and convexity between the lower frequencies being in series resonances, The frequency is parallel resonance. Due to the characteristics of the crystal itself, the distance between the two frequencies is quite close. In this very narrow frequency scale, the crystal is equivalent to an inductance, so it is only necessary to connect the two ends of the crystal in parallel. Circuit. This parallel resonant circuit is added to a negative
Feed circuit can be constructed sine wave vibration circuit, that is, crystal oscillator circuit.
Crystal capacitor effect of the size of the capacitor is not fixed value. Usually twenty or thirty p. Crystal is to give the microcontroller signal to the operation. This pulse is the operating speed of the microcontroller. For example, 12M crystal. SCM operating speed is 12M per second. And the computer's CPU concept is the same. of course. The operating frequency of the microcontroller is large. Not too big.
Usually 24M is not up. Otherwise not stable.
Grounding the words of the digital circuit to get chaos it does not matter. There is no analog circuit on the board. Grounding is not fixed. Usually connected in series. From small signal to large signal followed by access. Then a small signal connected to the power supply. There is a transformer connected to the transformer next to it.
Numerically separated. Do not leave the power supply does not form a loop.
This is due to the crystal oscillator and the microcontroller XTAL0 and the foot XTAL1 constitute the vibration circuit will occur gapping wave (that is, do not expect the existence of other frequencies of the wave), the wave of the impact of the circuit is not, but will reduce the circuit The stability of the clock vibrator.
For the sake of the stability of the circuit, ATMEL company only claims that the two pins in the crystal at the junction of two 10pf-50pf ceramic capacitor ground to reduce the impact of the wave on the stability of the circuit, so the capacitance of the crystal with 10pf -50pf can be between, there is no calculation formula.
But the main stream is to access two 33pf ceramic capacitors, so still with the main stream.