This page is the summary of me reading the reference manual, If there are missing info or incorrect info, please contact me at [email protected]

Different Types of Clocks & Terminology

• HSI (High speed internal clock) - Runs at 16MHz on the STM32, up to 1% Error
• HSE (High speed external clock) - More precision, external oscillator
• LSI (Low speed internal clock) - runs at 32KHz, used mostly for watchdog
• LSE (Low speed external clock) - more precision as LSI
• PLL (Phase locked loop) - pass in an input, then scale it up

Another quick definition

• RCC (Reset & Clock Controller) - Clock controller, controls buses and system clocks

Types Of Reset

System Reset

Basically non-loss-of-power reset. Can be generated by the below

• NRST pin is pulled low (via the RESET Button on the NUCLEO)
• WWDG (Windows watchdog) reached end of count
  • basically, this is the one that uses SYSCLK and must be refreshed periodically to avoid triggering a reset
• IWDG (independent watchdog) reached end of count
  • this is the one that uses LSI, same exact thing basically but on a separate clock
• SW generated reset
  • SYSRESETREQ bit in interrupt controller and RCC, setting that will trigger SW reset (this in CORTEX-M7 docs)
  • You can see where the reset came from via the RCC_CSR register
• Low power management Reset
  • When you enter standby mode or enter stop mode
  • Turn this on via turning off nRST_STDBY and nRST_STOP bits in user option bytes