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Clock configuration for stmf411 series mcu

Question asked by Teja on Mar 28, 2016
Latest reply on Mar 28, 2016 by Clive One
Hi STM,

As part of our project we are using STM32F411RET6 series MCU, We have followed clock configuration from the below link
http://www.st.com/web/en/catalog/tools/PF257927

As Maximum clock for the MCU what we are using is 100Mhz.
And our requirement is
*    mcu has run at 100Mhz or (Maximum clock)
*    We are using SPI peripheral and TIM7 in which both are using APB1 clock .

below are clock configuration we are using and we have on board external 26Mhz  crystal oscillator

cpu_clock                 : 100000000
HSE_SOURCE                : RCC_HSE_ON
AHB clock divder          : RCC_SYSCLK_Div1
APB1 clock divder         : RCC_HCLK_Div4
APB2 clock divder         : RCC_HCLK_Div2
Pll source                   : RCC_PLLSource_HSE
PLLM                       : 13
PLLN                       : 200
PLLP                       : 4
PLLQ                       : 9
System clock source       : PLL clock
systick clock source      : SysTick_CLKSource_HCLK
Internal flash wait state : 3 cycles

Below is my Brief understanding about the configuration

cpu clock is at 100 Mhz
AHB clock at 100 Mhz
APB1 clock at 100/4 = 25 Mhz
APB2 clock at 100/2 = 50 Mhz

Please let me know my understanding is right.

Now Question is, from clock configuration tool if Cpu clock is running at 100 Mhz( possible max speed ) max APB1 clock is 36Mhz from above configuration APB1 is 25Mhz, which is impacting throughtput of SPI periphral what we are using. And at the same time we are using TIM7 for internal monitoring purpose. Is there any way to bump up the APB1 clocks so that it can run at its maximum speed(36Mhz).

From clock configuration tool if cpu_clock is 72Mhz then APB1 is running at is maximum speed i.e., 36Mhz, but we dont want cpu clock to run at lower speed.

Please provide us a solution which unblocks us.

Please let me know if any more data needed.

Thanks & Regards,
Teja.

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