Crystal oscillator is the abbreviation of timely oscillator, which is called crystal in English. Crystal oscillators can be divided into active crystal oscillators and passive crystal oscillators. Its function is to generate an oscillating current in the circuit and send out a clock signal. It is the most important component in clock circuit, and its function is to provide reference frequency for IC and other components. It's like a balance. The unstable working frequency will cause the unstable working frequency of related equipment, which is naturally prone to problems. Due to the continuous improvement of manufacturing technology, the important technical indexes such as frequency deviation, temperature stability, aging rate and sealing performance of the crystal oscillator are very good, and it is not easy to break down, but you can still pay attention to the quality of the crystal oscillator when purchasing.

In the microcomputer system, the reset circuit is an important part to ensure the stable and reliable operation of the circuit. The first function of the reset circuit is to power on and reset. Generally, the power supply required for normal operation of microcomputer circuits is 5V 5%, that is, 4.75~5.25V Because microcomputer circuits are sequential digital circuits, stable clock signals are needed. Therefore, when the power supply is turned on, only when VCC exceeds 4.75V and the crystal oscillator works stably, the reset signal is removed and the microcomputer circuit starts to work normally. So far, there are two kinds of reset circuits for single chip microcomputer: one is power-on reset and the other is manual reset. The reset principle is shown in figure 1:

Figure 1: reset circuit of single chip microcomputer

Power-on reset principle: VCC is powered on, C is charged, and a voltage appears on the resistor 10K to reset the single chip microcomputer; After several milliseconds, C is full, the current on 10K resistor drops to zero, and the voltage is also zero, which makes the single chip microcomputer enter the working state.

Manual reset principle: discharge according to s and c during operation. S let go, C charged again, and a voltage appeared on the resistor of 10K, which reset the microcontroller. After a few milliseconds, the single chip microcomputer entered the working state. ?

That's how my thesis was written. I wonder if it will help you.