Ordinary crystal oscillators can be roughly divided into ceramic crystal oscillators and quartz crystal oscillators. There are also some special crystal oscillators. Such as constant temperature crystal oscillator, temperature compensated crystal oscillator 　　The crystal oscillator is an oscillator that uses a quartz crystal. Its accuracy is very high, and it can generate a very stable frequency, and its thermal stability is better than that of a discrete component oscillator. From the point of view of function, it can be said that the crystal oscillator is the "heartbeat" generator of each board. If the "heartbeat" of a person is disordered, it will be sick. Similarly, if the "heartbeat" of the computer board is disordered, various strange faults will also occur