Reset and clock control (RCC) STM32L

Reset:

1、系统复位：A system reset sets all registers to their reset values except for the RTC, RTC backup
registers and control/status register, RCC_CSR

      复位源查看：RCC_CSR

      Option byte loader：STM32L15xxx Flash programming manual (PM0062)

2、Power Reset:A power reset sets all registers to their reset values including for the RTC domain

3、RTC and backup registers reset：

复位源：A software reset, triggered by setting the RTCRST bit in the RCC_CSR register

Power reset (BOR/POR/PDR)

Clocks:

各时钟的特点：

1、HSE：高精度

2、HSI:低成本，比HSE具有更快的启动时间

3、MSI:复位、唤醒时。MSI为系统时钟。

降低功耗和唤醒时间

4、PLL：provide a 48 MHz clock to the USB or SDIO。为VCORE的各个range进行倍频

5、LSE:低功耗，高精度。用于RTC/日历、定时等

6、LSI:低功耗。停止待机模式下为IWDG提供时钟

系统时钟源：HSI,HSE,PLL,MSI

时钟安全系统：当外部时钟失效时採取对应措施以保护应用的执行

RTC与LCD的时钟源：LSE或LSI

Watchdog clock：LSI

MCO:时钟输出pin(PA8)

时钟的測量：TIM9/TIM10/TIM11