STM32H7S3V8T6 TIM1 prescaler clock clarification

[JShro]

Hi All, 

Hoping someone can clarify my confusion on the clock input for the TIM1 counter...

background:

I am testing Tim1 output compare by toggling PA8 on the micro... - the timer settings are

period = 1600, no clock divisor or prescaler and my clock config is below

On the scope I see PA8 toggling with a period of 25us which seems kind a strange... 

So even if I assume a counter clock of 150Mhz (APB1, APB2 peripheral clocks) and the formula of clock/2*(period+1) as the frequency I should see it toggle at 21.34 us?

Why this discrepancy??

Thanks!

[waclawek.jan · Accepted solution]

At this point it appears that your clocks are not set up as you expect.

What's your primary clock source? Have you checked it e.g. by outputting it to a MCO pin?

JW

[JShro]

Yes! That was it...

I have a 16MHZ xtal as the clock input, addly enough the MCO pin was showing the correct clock, however the PWR->CFG2 even though it has LDEN set to 1 was not working until you set it again prior to setting the VOS for high speed...

I found a similar issue reported by another user - https://community.st.com/t5/stm32cubemx-mcus/stm32h747-freezes-waiting-for-vosrdy/td-p/304569/page/2

Nevertheless - setting LDEN again prior to the VOS took care of the issue and the timer output is now correct.

Thanks for all your suggestions/help  - As usual occams razor always works wonders :)