Clock sources are generally divided into two categories
: 1. Internal clock: the system starts the default clock
2. External clock: higher precision and stability.
Internal and external are divided into high-speed and low-speed.
The main clock of the high-speed clock chip,
the low-speed clock, the real-time clock and the watchdog
clock Operating mechanism
After the chip is started, the internal high-speed clock is used as the start-up clock source by default. After starting, the external clock is selected to be used. The external clock is first amplified by frequency multiplication and then confirmed by the internal switch. The main clock frequency is then divided to other peripherals on the clock line
. There are basically 3 types
: 1. Main frequency clock: core clock/memory/DMA
2. Secondary frequency clock: synchronized with the main frequency and independent, it can be used as the clock basis when the main frequency sleeps, such as sleep wake-up interrupt, etc.
3. Peripheral clock : Communication driver/TIM/ADC/GPIO
Reference:
Graphics and texts teach you to understand the STM32 clock of the microcontroller