Does STM32C071CBT6 support PLL for external oscillator?

[curiocity]

I am using an 8 MHz external oscillator and was planning to use a PLL to increase the system frequency. However, when I open the Clock Configuration tab in CubeMX, I don’t see any option for a PLL.

I’ve also shared a screenshot of the clock configuration where it’s clear that the PLL option is not available.

So my question is: Does the STM32C071CBT6 microcontroller support PLL with an external oscillator?

[Andrew Neil · Accepted solution]

What makes you think the STM32C071CBT6 has a PLL?

There is no mention in the Datasheet

That would explain why CubeMX doesn't show it

[Andrew Neil]

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@Andrew Neil wrote:

There is no mention in the Datasheet

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however, there are three mentions in the Reference Manual:

https://www.st.com/resource/en/reference_manual/rm0490-stm32c0-series-advanced-armbased-32bit-mcus-stmicroelectronics.pdf

via: https://www.st.com/en/microcontrollers-microprocessors/stm32c071cb.html#documentation

@STTwo-32 These look like copy-paste errors in the RM ?

[STTwo-32]

Hello @Andrew Neil 

I've escalated this to the doc team for review (under internal ticket number 212567).

Best Regards.

STTwo-32

[curiocity]

Hi @STTwo-32

Is it possible to quickly confirm whether the PLL can be used with an external oscillator on the STM32C071CBT6?

Based on Cube MX and Andrew's suggestion, I am assuming that the STM32C071CBT6 does not support PLL functionality.

[Andrew Neil]

The STM32C071CBT6  does not have a PLL - so it cannot "support" a thing it doesn't have!

What made you think it does have a PLL ?

[curiocity]

Hi Andrew,

Thank you for your quick response. I was reviewing the user manual and came across a statement that says, "Optionally turn ON external Oscillator and/or device PLL." This wording left me a bit confused, so I just wanted to confirm whether the PLL can actually be used in this case.

[curiocity]

@Andrew NeilBy the way, if the CUBE MX software does not provide a configuration option for the PLL, then I will stop exploring this further for now.

[Andrew Neil]

As noted earlier, those look like  copy-&-paste errors - and @STTwo-32 is looking into it.

If the PLL existed, it would be documented in the RM, and would appear in the Clock Tree:

https://www.st.com/resource/en/reference_manual/rm0490-stm32c0-series-advanced-armbased-32bit-mcus-stmicroelectronics.pdf#page=123