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WM_IR
WM_IR
Associate III
July 3, 2022
Solved

NEED CLARIFICATION TIMER INTERRUPT FORMULA

I have read a book on stm32, and inside the timer topic, it is stated that a formula to determine the values to be loaded to generate interrupt at specified times which as below:

0693W00000QKKUtQAP.jpgMy question is does this formula applicable for all stm32 timers? and another question is, I could not find this formula in reference manual for model stm32L476RG. Could someone show me where to get this formula from official ST documentation?

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KnarfB
KnarfBBest answer
Super User
July 3, 2022

The official source is the reference manual, in your case RM0351 "STM32L47xxx, STM32L48xxx, STM32L49xxx and STM32L4Axxx advanced Arm®-based 32-bit MCUs". The formula may not be stated explictely, but can be dervived from the texts, like

33.4.7 ... "The counter clock frequency CK_CNT is equal to f_CK_PSC / (PSC[15:0] + 1)."

33.3.2 Counting mode, see the diagrams.

hth

KnarfB

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2 replies

Tesla DeLorean
Tesla DeLorean
Guru
July 3, 2022

The TIM use N-1 values for the Prescaler and Period counters as these are the simplest to implement. ie simple comparator of last value so next clock rolls into Update​ / Zero load.

​

i​e Period = 9, has 10 states, 0 .. 9, repeating

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KnarfB
KnarfBBest answer
Super User
July 3, 2022

The official source is the reference manual, in your case RM0351 "STM32L47xxx, STM32L48xxx, STM32L49xxx and STM32L4Axxx advanced Arm®-based 32-bit MCUs". The formula may not be stated explictely, but can be dervived from the texts, like

33.4.7 ... "The counter clock frequency CK_CNT is equal to f_CK_PSC / (PSC[15:0] + 1)."

33.3.2 Counting mode, see the diagrams.

hth

KnarfB

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