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Tim 3 Clock Frequency Understanding

Question asked by asl.sean on Feb 26, 2014
Latest reply on Feb 26, 2014 by waclawek.jan
Hi i am referring to an example from the stm32f4 library.
In the comment section :

TIM3 Configuration: Output Compare Toggle Mode:
 
In this example TIM3 input clock (TIM3CLK) is set to 2 * APB1 clock (PCLK1),
since APB1 prescaler is different from 1.  
  TIM3CLK = 2 * PCLK1 
  PCLK1 = HCLK / 4
  => TIM3CLK = HCLK / 2 = SystemCoreClock /2


My question is why is TIM3CLK = 2 * PLK1 shouldnt it be

TIM3CLK = APB1 = HCLK /4 ?

And what does it mean by 

TIM3 input clock (TIM3CLK) is set to 2 * APB1 clock (PCLK1)

Isnt TIM3 input clock by default APB1 ?

Thanks. 

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