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Uwe Bonnes
Uwe Bonnes
Chief
October 26, 2015
Question

Half cycle acces ob F1/F3

  • October 26, 2015
  • 4 replies
  • 779 views
Posted on October 26, 2015 at 15:56

Hello,

what is Half-cycle access  (FLASH_ACR_HLFCYA) for? It may be used with slow clocks ( < 8 MHz)  and AHB divisior = 1.

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    4 replies

    Nesrine M_O
    Nesrine M_O
    Associate
    October 26, 2015
    Posted on October 26, 2015 at 16:48

    Hi bonnes.uwe,

    Half cycle configuration is not available in combination with a prescaler on the AHB. The system clock (SYSCLK) should be equal to the HCLK clock. 

    This feature can therefore be used only with a low-frequency clock of 8 MHz or less. It can be generated from the HSI or the HSE but not from the PLL.

    -Syrine-

    Uwe Bonnes
    Uwe BonnesAuthor
    Chief
    October 26, 2015
    Posted on October 26, 2015 at 17:26

    Dear Syrine,

    your response repeats what is written in the reference manuals. But is does not answer what Halfcycle access is good for!

    Nesrine M_O
    Nesrine M_O
    Associate
    October 26, 2015
    Posted on October 26, 2015 at 17:55

    Hi bonnes.uwe,

    Half Cycle Enable Access, if it is set, it halves the period during the flash signals are driven high to save power consumption.

    -Syrine-

    waclawek.jan
    waclawek.jan
    Super User
    October 26, 2015
    Posted on October 26, 2015 at 22:10

    Syrine,

    Thanks for your answer.

    Can this info be added to the relevant RMs, please?

    Is the upper bound to using this exactly 8MHz? Can this be clearly stated too?

    And can the power saving be quantified, best in the datasheet, please?

    Thanks

    Jan Waclawek

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