STM32H7 traceclkin source

[drath]

Hi all,

I'm trying to understand what source the STM32H7 (specifically STM32H743) uses for the TPIU trace clock.

According to the RCC chapter there ought to be a multiplexer that allows to choose from a number of sources:

According to the debug chapter, it is derived from the pll1_r_ck (no mention of the other options show above):

Is this clock multiplexer for traceclkin actually implemented, or is it fixed to pll1_r_ck? If this multiplexer is actually implemented, how is it controlled, i.e. which register/bits?

Best Regards,

Dominic

[SofLit]

Hello @drath and welcome to the community.

I'm checking internally and get back to you as soon as I have a feedback (internal ticket number for follow-up 193043)

Thank you for this contribution.

[drath]

I believe I can answer my own question:

The traceclkin switch is controlled by RCC_CFGR[SW]. While that field is documented to switch the system clock (sys_ck), I guess we can assume that this actually switches both sys_ck and traceclkin in parallel. This is what the blockdiagram shows and it matches our observations, even if the RCC_CFGR documentation doesn't explicitly mention it.

Regards,

Dominic

[SofLit · Accepted solution]

Indeed, The Clock source is controlled by SW field in RCC_CFGR register. A field common to both System clock and trace clock:

And if the system clock is on PLL1_p trace clock will be on PLL1_r otherwise it will be on HSE, HSI or CSI.

So please mark the solution.