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Associate III
January 24, 2025
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STm32f407: Which Registers control HSI or HSE oscillator selection and PLL clock source?

  • January 24, 2025
  • 2 replies
  • 537 views

Hi 

I want to understand "which register decides whether HSI or HSE oscillator is selected for PLL clock source in STM32F407"(selection of the HSI or HSE oscillator as PLL clock source"

B.R

Ash

Best answer by STTwo-32

Hello @Ash1 

According to the RM0090, the PLL source is selected throw the PLLSRC bit of the RCC_PLLCFGR register:

STTwo32_0-1737713948847.png

For your coming requests, please have a look at our documents, almost all details are well provided there as said @Andrew Neil .

Best Regards.

STTwo-32

2 replies

Andrew Neil
Super User
January 24, 2025

See the Reference Manual - it will be linked from the 'Documentation' tab on the Product Page for the chip.

You'd need to give the full part number (not just STM32F407) to get to the correct page.

 

You can also configure it graphically using CubeMX (either standalone or within CubeIDE), then examine the generated code.

 

BTW: I edited your title - just "STM32F407" doesn't give much indication of what the thread is actually asking.

 

A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
STTwo-32
STTwo-32Best answer
Technical Moderator
January 24, 2025

Hello @Ash1 

According to the RM0090, the PLL source is selected throw the PLLSRC bit of the RCC_PLLCFGR register:

STTwo32_0-1737713948847.png

For your coming requests, please have a look at our documents, almost all details are well provided there as said @Andrew Neil .

Best Regards.

STTwo-32

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