Function CMU_ClockDivSet

bsp/efm32/Libraries/emlib/src/em_cmu.c:738–906

/ * @brief * Set clock divisor/prescaler. * * @note * If setting a LF clock prescaler, synchronization into the low frequency * domain is required. If the same register is modified before a previous * update has completed, this function will stall until the previous * synchronization has completed. Please refer to CMU_FreezeEnable() for * a suggestion on how to reduce stalling

 *   The clock divisor to use (<= cmuClkDiv_512).
 ******************************************************************************/
void CMU_ClockDivSet(CMU_Clock_TypeDef clock, CMU_ClkDiv_TypeDef div)
{
  uint32_t freq;
  uint32_t divReg;

  /* Get divisor reg id */
  divReg = (clock >> CMU_DIV_REG_POS) & CMU_DIV_REG_MASK;

  switch (divReg)
  {
#if defined (_EFM32_GIANT_FAMILY)
  case CMU_HFCLKDIV_REG:
    EFM_ASSERT((div>=cmuClkDiv_1) && (div<=cmuClkDiv_8));

    /* Configure worst case wait states for flash access before setting divisor */
    CMU_FlashWaitStateMax();

    /* Set divider */
    CMU->CTRL = (CMU->CTRL & ~_CMU_CTRL_HFCLKDIV_MASK) |
      ((div-1) << _CMU_CTRL_HFCLKDIV_SHIFT);

    /* Update CMSIS core clock variable */
    /* (The function will update the global variable) */
    freq = SystemCoreClockGet();

    /* Optimize flash access wait state setting for current core clk */
    CMU_FlashWaitStateControl(freq);
    break;
#endif

  case CMU_HFPERCLKDIV_REG:
    EFM_ASSERT((div >= cmuClkDiv_1) && (div <= cmuClkDiv_512));
    /* Convert to correct scale */
    div = CMU_DivToLog2(div);
    CMU->HFPERCLKDIV = (CMU->HFPERCLKDIV & ~_CMU_HFPERCLKDIV_HFPERCLKDIV_MASK) |
                       (div << _CMU_HFPERCLKDIV_HFPERCLKDIV_SHIFT);
    break;

  case CMU_HFCORECLKDIV_REG:
    EFM_ASSERT(div <= cmuClkDiv_512);

    /* Configure worst case wait states for flash access before setting divisor */
    CMU_FlashWaitStateMax();

    /* Convert to correct scale */
    div = CMU_DivToLog2(div);

    CMU->HFCORECLKDIV = (CMU->HFCORECLKDIV & ~_CMU_HFCORECLKDIV_HFCORECLKDIV_MASK) |
                        (div << _CMU_HFCORECLKDIV_HFCORECLKDIV_SHIFT);

    /* Update CMSIS core clock variable */
    /* (The function will update the global variable) */
    freq = SystemCoreClockGet();

    /* Optimize flash access wait state setting for current core clk */
    CMU_FlashWaitStateControl(freq);
    break;