Can't enter VLP mode on Kinetis KL14

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Can't enter VLP mode on Kinetis KL14

Contributor IV


I can't entre VLP mode in my Kinetis KL14. The funcion VLPModeEnable hangs in the following while (marked in blue):

VLPModeEnable - where the app "stops"

LDD_TError Cpu_VLPModeEnable(void)


  if  (ClockConfigurationID != 1U) {

    return ERR_SPEED;                  /* Very low power mode not enabled in the active clock configuration. */


  if (SMC_PMSTAT == 0x04U) {           /* If the system is already in VLP mode, return */

    return ERR_OK;


  /* SMC_PMCTRL: ??=0,RUNM=2,??=0,STOPA=0,STOPM=0 */

  SMC_PMCTRL = (SMC_PMCTRL_RUNM(0x02) | SMC_PMCTRL_STOPM(0x00)); /* Enable very low power mode */

  while(SMC_PMSTAT != 0x04U) {         /* Wait until in the Very Low Power run mode */


  return ERR_OK;


Indeed I had this problem before and solved it by manually disabling a timed interrupt via a timer unit by calling TU1_Disable function before entering VLP.

I've been developing for a couple months and now the problem showed up again, but this time I can't figure the solution out.

Here is how I enter in VLP mode (I'm using User enter choice in PE options, so it is not entering VLP automatically when I set the corresponding clock configuration):

Entering VLP
/* important: theoretically the SetClockConfiguration function below should disable it,
* however in practice the TU1 must be disabled before it */

/* set clock to configuration 1 (internal clock, BLPI, 0.03125 MHz) */
/* enter in low power mode */

And here is what I do when I want to return to Normal Mode:

Exiting VLP

/* disable Very Low Power Run Mode */


  /* set high frequency clock configuration - 16MHz */


  /* reenable TU1 PE device - see comment on TU1_Disable command below */



I know the TU and PWM stuff should be done internally by the PE, but  this was the only way it worked before.

The question is: what could be preventing me from entering VLP?

Thank you very much!

Luiz Fernando

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Senior Contributor I

Hi Luiz:

I recommend you to check out this app note, specially 4.4 VLPR (Very Low Power Run).