S32K328 RTC FAIL AFTER WAKEUP

[Wade0905]

Hello NXP Team,

I have previously developed RTC functionality on the S32K314, and after sleep wake-up it can continue counting time normally.

Now I am porting the project to the S32K328. However, while porting the RTC function, I encountered an issue:

After wake-up, the date (year/month/day) is reset to the default value 1970/1/1. In addition, the time (hours/minutes/seconds) does not preserve the originally configured value, but instead reflects only the elapsed time counted from the RTC start point.

For example, I initialize the RTC to 2026/05/08 05:06:07. After 1 minute of operation, when the MCU wakes up and I read back the RTC time, the date has reverted to 1970/01/01, and the time shows 00:01:00 instead of the expected 05:07:07.

This issue did not occur on the S32K314. What could be the possible causes of this problem?

Thank you.

[Julián_AragónM]

Hello @Wade0905,

Have you checked RTC clock source? Confirm if SIRC and "Enabled in Standby" options are selected:

Also, keep in mind that RTC counter value will not be reset after wake-up, but it will reset by calling RTC initialization code in main.c. I can see you initialize RTC only after wake-up event. You can try reading reset reason to see if any other type of reset is being issued, and thus, clearing RTC value by mistake.

There is a community post you can refer to: S32K312: RTC- Preserving RTC counter value from getting resets once after every wakeup.

Please compare it to your configuration.

Best regards,
Julián

[Wade0905]

Hi Julián,

Thanks for your reponse.

Regarding clock source, I select SXOSC which same as our project in S32K314. Please see below picture for you ref.

Regarding init, I only do rtc_app_init() when WAKEUP_REASON != MCU_WAKEUP_REASON which same as our project in S32K314. Please see below picture for you ref.

I believe the counter continues counting during sleep mode, but the date and time are reset.
You can refer to my test results below.

At the first power-on, after rtc_app_init() is completed, the system starts counting from 2026/05/08, 5 hours, 6 minutes, and 7 seconds.

This is transmitted via CAN message 0x521.

• BYTE 0: Year
• BYTE 1: Month
• BYTE 2: Day
• BYTE 3: Hour
• BYTE 4: Minute
• BYTE 5: Second
• BYTE 7: RESET REASON

 

After waking up from sleep for five minutes, the counter (CNT) continues counting. However, the year, month, day, hour, minute, and second all start counting from 1970/01/01 00:00:00, instead of continuing from the time set during initialization.

For 0x263, BYTE 2 to BYTE 5 represent the time extracted using Rtc_Ip_ConvertTimeDateToSeconds().

Please check the differences between the S32K328 and S32K314.

Why does the RTC on the S32K328 not retain the previously configured date and time, even though the same settings work correctly on the S32K314?

[Julián_AragónM]

Hi 

Are you able to share your project, or the .mex configuration file, so I can inspect the code on my side? 

The only reasons I can think of for the RTC not keeping the value are:

1. Reset reason is other than Wake-Up and value is not kept since reset is non-functional. 
2. Even if reset reason is functional, it may not be wakeup, meaning the RTC is being re-initialized.

You've mentioned that byte 7 shares reset reason, however I cannot see in the images which reset reason is being sent over CAN. MCU_WAKEUP_REASON is declared as 28 inside the Power_Ip_Specific.h, I imagine CAN must send a 28? 

If you are using MCAL, make sure the option "GPT Standby Wakeup Support" is enabled: S32K324 RTC value not preserved after sleep.

One thing I can suggest is to do a register dump (through the "Watch Registers" view). This may help you spot any differences between projects. Simply export both S32K328 & S32K314 register values as files, and you can compare them through any program, for example WinMerge.

Best regards,
Julián

[Wade0905]

Hi Julián,

Reset reason is 0x1C(28). If re-init happened, date and time should be 2026/5/8 05:06:07 which same as I set in rtc_app_init(). Besides, as I mentioned, I can see that the counter (CNT) continues counting, as the seconds value obtained using Rtc_Ip_ConvertTimeDateToSeconds() keeps increasing even after the MCU wakes up from standby mode.

I see the same problem in NXP Community for S32K328.

https://community.nxp.com/t5/S32K/S32K328%E5%86%85%E9%83%A8%E7%9A%84RTC%E6%98%AF%E4%B8%8D%E6%98%AF%E...

The .mex configuration file will be sent to you separately.

The RTC and standby-related code are as follows.

Executed once during initialization; not executed upon wake-up.

rtc_app_main() is executed every 500 ms.

mcu_standby_service() is executed once before entering standby mode.

Wade

[Julián_AragónM]

Hello @Wade0905,

Sorry for the late reply. Please see some comments below:

1. The .mex you've shared does not include any configuration for RTC. Please check the file and send it again if possible.

2. Actually. Rtc_Ip_Init() function is already standby-wakeup aware, and will skip software reset of the module if RTCC_CNTEN is already set:

Simply enable GPT Standby Wakeup Support:

With this, you can just keep the Rtc_Ip_SetTimeDate() API inside the if instruction:

/* Clear RDSS to prevent automatic wake up after setting RDSS during standby */
resetReason = Power_Ip_GetResetReason();

Rtc_Ip_Init(RTC_INST, &RTC_0_InitConfig_PB);
Rtc_Ip_EnableInterrupt(RTC_INST, RTC_IP_COUNTER_INTERRUPT);
Rtc_Ip_StartCounter(RTC_INST);

if(resetReason != MCU_WAKEUP_REASON)
{
Rtc_Ip_SetTimeDate(RTC_INST, &Rtc_DateTimeCfg_0);
}

Date and Time data are software based, while the RTC counter is hardware based. So, if MCU does not execute software to re-calculate year, month, and data after exiting standby, date and time will be showing the same after every wakeup. 

I've created a simple example for S32K3X8EVB, as there is no evaluation board for S32K328. It simply configures two GPIO wakeups, and depending on which SW is pressed, either the RTC counter + date will be printed, or MCU will enter standby.

It even prints reset reason (28 for wakeup, 0 for power on reset, etc.), which helps identify whether a functional or destructive reset was done:

Hope it helps.

Best regards,
Julián

[Wade0905]

Hi Julián,

 .mex will send to you in private message.

I will try to follow and replicate your .mex configuration settings.
However, I noticed that in your test results, the date always starts from 1970/01/01, because the issue I am seeing is also that the date resets and starts counting again from 1970/01/01.

Could you try setting a different date before entering sleep mode and test again?

Thank you.

Wade

[Julián_AragónM]

Hi @Wade0905,

Thank you for sharing your .mex file. Configuration for POWER and RTC modules seem to be correct.

Could you try setting a different date before entering sleep mode and test again?

Yes, as I've mentioned, date and time data are software based, while the RTC counter is hardware based. While the RTC counter keeps counting in standby, actual date and time is still re-calculated at wake up.

So, if MCU does not execute software to re-calculate year, month, and data after exiting standby, date and time will be showing the same after every wakeup. 

You can try creating a "restore RTC context" function or use Standby RAM (kept alive through standby and wake up) to keep the date & time data in place. 

There are some standby RAM examples in these community posts:

• S32K3 Low Power Management AN and demos
• [RTD600 MCAL & IP] S32K3 Low Power Management AN and demos

Best regards,
Julián