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jonathan239955_stm1_st
jonathan239955_stm1_st
Associate II
August 25, 2016
Question

STM32L476 ClockDivision

  • August 25, 2016
  • 2 replies
  • 855 views
Posted on August 25, 2016 at 09:59

Hello,

I am using the board Nucleo-L476RG, the system core clock is running at 80 Mhz. I don't understand what is the purpose of ClockDivision. I thought that I can divide the frequency by 4 if I setTIM_CLOCKDIVISION_DIV4 but it's not working. I am usingPrescaler, but it's not enough because I need to count around 60sec using 16bit timer. Here is my code to have a 500 Hz frequency 80Mhz/ ((Prescaler+1)*

ClockDivision

) = 500 

timer.Instance = TIM6;
timer.Init.Period = 0xffff; 
timer.Init.CounterMode = TIM_COUNTERMODE_UP;
timer.Init.Prescaler = 40000 - 1;
timer.Init.ClockDivision = TIM_CLOCKDIVISION_DIV4; // has no effect
timer.Init.RepetitionCounter = 0;
HAL_TIM_Base_Init(&timer);

Thanks for your help,
    This topic has been closed for replies.

    2 replies

    Walid FTITI_O
    Walid FTITI_O
    Visitor II
    August 25, 2016
    Posted on August 25, 2016 at 10:36

    Hi constant.jonathan, 

    The Timer clock division CKD does not relate to the time-Base update. The prescaler and period does.

    As mentioned in the corresponding register in reference manual, it is related ti the dead time configuration.

    ''Bits 9:8

    CKD[1:0]

    : Clock division

    This bit-field indicates the division ratio between the timer clock (CK_INT) frequency and the

    dead-time and sampling clock (t

    DTS

    )used by the dead-time generators and the digital filters

    (TIx)'

    -Hannibal-

    Tesla DeLorean
    Tesla DeLorean
    Guru
    August 25, 2016
    Posted on August 25, 2016 at 19:45

    Yes, unrelated to what you think it is does.

    Use a 32-bit counter, use one that has a Repetition Counter setting the timebase to 1sec and repeat 60 times, the Update Interrupt will fire once a minute.

    Use the RTC?

    Use the 1ms/1KHz timer to count off time?

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