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jeffreytstringer
jeffreytstringer
Visitor II
March 4, 2015
Question

STM32CubeMX Clock Configuration Problem

  • March 4, 2015
  • 1 reply
  • 893 views
Posted on March 04, 2015 at 23:44

I'm trying to use Cube for an STM32F042 project and I'd like the APB1 peripheral clock to be 1 MHz but Cube is saying that the minimum APB1 peripheral clock is 10 MHz. Is this true or is this a problem with Cube? If it does need to be 10MHz or higher where does it say this in the documentation, I couldn't find it.

I've included a screen shot of the parameters and the red box.

Thanks,

Jeff

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    1 reply

    Tesla DeLorean
    Tesla DeLorean
    Guru
    March 4, 2015
    Posted on March 05, 2015 at 00:55

    In general I'd expect the design to be fully static, ie you can stop the clock completely without loss of state.

    At some point some peripheral may become unusable because the clocking scheme can't get them to run at the rates you want. ie can you get to 115200 baud at 1 MHz?

    What may be a problem is clock inversion, for example you can't run APB1 faster than APB2. Perhaps those peripherals clocking at 8 MHz won't play well with a 1 MHz bus, or issues with the bus servicing something quickly enough (APB vs SDIO in some designs) or where FIFO's get filled faster than they can be emptied, systemically. A DMA contention to a slower bus just choking everything.

    So figure inversion issues, or too large a disparity.

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