topic Re: IRTC Tamper check - LLWU - MKM34/35Z in Kinetis Microcontrollers

IRTC Tamper check - LLWU - MKM34/35Z

Bhagavan — Tue, 10 Feb 2026 09:46:22 GMT

Hello,

MCU - MKM34/35Z - SDK Based application

SDK: SDK_2.x_TWR_KM35Z75M ver. 25.06.00

IDE: MCUXpresso IDE v25.6

Application: MCU is always in VLLS2 sleep mode, and one GPIO pin (PTG6_LLWU0) along with the Tamper0 pin (IRTC Tamper) are configured as wake-up sources. An interrupt on either pin should wake the system.

The GPIO pin behaves as expected and successfully wakes the system from VLLS2. However, the Tamper pin does not wake the system, even though it is configured exactly according to the reference application.

I am sharing the relevant code snippets for reference and would appreciate help in identifying the issue.

void RTC_TamperInit(void)
{
CLOCK_EnableClock(kCLOCK_Rtcreg);
CLOCK_EnableClock(kCLOCK_Rtc0);

IRTC_GetDefaultConfig(&irtcConfig);
irtcConfig.timerStdMask = true;
irtcConfig.wakeupSelect = true;

if (IRTC_Init(RTC, &irtcConfig) == kStatus_Fail)
{
return;
}

IRTC_SetOscCapLoad(RTC, kIRTC_Capacitor2p|kIRTC_Capacitor4p|kIRTC_Capacitor16p);

tamper0Config.filterClk = kIRTC_4;
tamper0Config.filterDuration = 2;
tamper0Config.pinPolarity = true;/*true is Active*/
IRTC_SetTamperParams(RTC, kIRTC_Tamper_0, &tamper0Config);

/* Lock tamper configuration */
IRTC_SetTamperConfigurationOver(RTC);

/* Enable RTC as LLWU wake source */
LLWU_EnableInternalModuleInterruptWakup(LLWU, LLWU_IRTC_IDX, true);

/* Clear stale flags */
IRTC_ClearStatusFlags(RTC, 0xFFFFFFFF);
IRTC_ClearTamperStatusFlag(RTC);
}

void LLWU_Init(void)
{
//GPIO PTG6
LLWU_SetExternalWakeupPinMode(LLWU, LLWU_WAKEUP_PIN_IDX, LLWU_WAKEUP_PIN_TYPE);
LLWU_ClearExternalWakeupPinFlag(LLWU, LLWU_WAKEUP_PIN_IDX);
//IRTC Tamper0
LLWU_EnableInternalModuleInterruptWakup(LLWU, LLWU_IRTC_IDX, true);
}

Thanks in advance for your help!

Re: IRTC Tamper check - LLWU - MKM34/35Z

erin77brown — Tue, 10 Feb 2026 10:29:29 GMT

Hello,
It appears your Tamper pin is failing to wake the MCU because the IRTC Tamper Interrupt is likely not enabled at the peripheral level, even though the LLWU is configured. While irtcConfig.wakeupSelect = true prepares the logic, you must explicitly call IRTC_EnableTamperInterrupt(RTC, kIRTC_Tamper0InterruptEnable) to allow the event to propagate. Additionally, ensure the Tamper 0 pin is not masked in the IRTC control registers and verify that the IRTC_SetTamperConfigurationOver (Lock) isn't being called before all flags are cleared, as this can sometimes prevent subsequent state changes from triggering the wakeup signal to the LLWU.

Re: IRTC Tamper check - LLWU - MKM34/35Z

Bhagavan — Tue, 10 Feb 2026 11:10:35 GMT

Thanks @erin77brown for your quick reply.

Sorry, I missed mentioning this earlier. I also tried enabling the interrupt using
IRTC_EnableInterrupts(RTC, kIRTC_TamperInterruptEnable); or RTC->IER |= RTC_IER_TAMPER_IE_MASK;, but unfortunately, it did not help, and the tamper pin does not wake the system.

Could you please confirm whether we must call the function: IRTC_SetTamperConfigurationOver(RTC); after clearing all flags?. Since we are already using IRTC_SetWriteProtection() to lock and unlock the RTC, I would like to understand the correct usage and sequence. If you have any example code, please share it—it would be greatly appreciated.

Thanks in advance.

Re: IRTC Tamper check - LLWU - MKM34/35Z

Alice_Yang — Wed, 11 Feb 2026 10:56:10 GMT

Hello @Bhagavan

Please check whether the Tamper Interrupt Status bit is set,

and also test whether other iRTC interrupts are able to wake up the system.

Alice

Re: IRTC Tamper check - LLWU - MKM34/35Z

Bhagavan — Mon, 16 Feb 2026 07:29:07 GMT

Hi,

It seems there is a problem with the IRTC internal (LLWU) module wakeup in the SDK example.

I have tried using the iRTC Tamper (LLWU_M3IF) and iRTC Alarm (LLWU_M1IF) wakeup sources as described in the MKM3x series Reference Manual, but it did not help.

If anyone has faced this issue, could you please share a solution or provide an example?

Thanks in advance for your help!

Re: IRTC Tamper check - LLWU - MKM34/35Z

Alice_Yang — Tue, 24 Feb 2026 08:34:58 GMT

Hello @Bhagavan

There is no official demo available for KM34.

However, the RTC module is the same as in the Kinetis series.

Please refer to: https://community.nxp.com/t5/Kinetis-Microcontrollers/LLWU-PORT-interrupt/m-p/266526

Alice