STM单片机具有四个晶振接口，两个在内部，两个在外部。系统工作一般需要

单片机具有四个晶振接口STM，两个在内部，外部在两个。系统和工作一般需要一个一个高频时钟低频时钟，高<br>频时钟为CPU内核，高频外设模块等提供时钟脉冲，低频时钟最好的，，等提供时钟脉冲的脉冲，，，，，，等提供<br>时钟脉冲的频率，并使其能够产生<br>高频脉冲。以以不同系统工作在一般的应用，的电路<br>精度要求不高要求不高，不ç了，又简化了了电路电路设计设计负担。在系统上，两个默认<br>晶振这的英文两个çRC晶振启动

STM MCU has four crystal oscillator interfaces, two inside and two outside. The system work generally needs a high frequency clock and a low frequency clock, high frequency clock<br>Frequency clock provides clock pulse for CPU core, high frequency peripheral and other modules, low frequency clock provides clock pulse for low frequency peripheral, timer and other modules<br>The power consumption is much higher than that of the low frequency clock. When the system does not need the high frequency clock, it can make the high frequency clock sleep and only support the low frequency clock, which means that the system remains ultra-low<br>Power consumption is the key. If necessary, it can wake up the high frequency clock to adapt to different system requirements. In the general application, the system is very sensitive to the clock circuit<br>The requirement of precision is not high, so it can not connect external crystal oscillator, which not only reduces the system power consumption, but also simplifies the burden of external circuit design. When the system is powered on, it is used by default<br>Two internal crystal oscillators, this is because the two internal RC crystal oscillators start fast<br>