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CCS/MSP430F6779A: RTC freezes when power is cut off and resumes when power is backed up.

Gaurav Kumar44
Prodigy 185 points
Part Number: MSP430F6779A
Other Parts Discussed in Thread: MSP430WARE, MSP430F6736

Tool/software: Code Composer Studio

Hi Everyone,

I am using MSP430F6779A for my project in which i am facing issue with RTC time. When power is cutoff my RTC freezes the last time and continues to run when power is restored. I need my RTC to continue running even during powerfail. I have connected battery on VBAT and i can see the crystal oscillating on my scope which ensures no fault in my hardware. I found one thread running on this forum relevant to my question e2e.ti.com/.../583815            . I have tried the answer mentioned in the same thread but my problem remains same. I tried with RTCLOCK and RTC_C also but of no use. I believe i have tried most of the online help online in this regards but could not solve my problem. I used MSP430Ware code to initialise my RTC for first but later on did many helpless experiments with that. Now i am here, anyone knowing the issue please help me asap.

One more thing here i want to mention that i am using MSP430F6736 for one more of my project in which my RTC runs as expected no issue with that. I tried same code of RTC but doesnt work out on 6779A.

Thank you so much in advance for anyone helping me out of this situation. This is the last hurdle my project is stuck for release

  • 0
    TI__Mastermind 28945 points
    Hey Gaurav,

    For MSP430F6779A, the Battery Backup only powers RTC_B. Can you confirm that you are using RTC_B for this testing and not RTC_C?

    Thanks,
    JD
  • 0 in reply to JD Crutchfield
    TI__Genius 14165 points
    Hi Gaurav, JD,

    based on F6779A datasheet SLAS982A it contains RTC_C. On the other site I want to understand failure mode a bit better.
    Stuck measn that if your remove DVCC and your core domain is powering down e.g. for 10s then the RTC_C does not count these 10s.
    If you power up again the RTC_C continoues at the time before the power down. Is this what you mean with stuck??

    You already checked that AUXVCC3 is stalbe and LFO is oscillating duing DVCC removal correct? You also do not have charger functionality from DVCC to AUXVCC3 enabled?

    And can you please also check if the high site SVS is alwasy enabled!
  • 0 in reply to Dietmar Walther
    Prodigy 185 points
    Hello Walther,
    thanks for your suggestions, although my issue is resolved now. And i suspect it was SVS though i didnt check it. And you understood my question rightly thats exactly what i meant by stuck. I am placing below my code so other need not face similar issue on 6779A...

    My one time RTC initialization looks like below
    PMMCTL0_H = 0xA5;
    RTCCTL0_H = RTCKEY_H;
    RTCCTL13 &= ~RTCLOCK;
    RTCCTL0_L |= RTCRDYIE;
    RTCCTL1 |= RTCHOLD | RTCMODE;
    RTCYEAR = 2019; // Year = 0x2011 = 2011
    RTCMON = 1; // Month = 0x12 = December
    RTCDAY = 1; // Day = 0x05 = 5th
    RTCDOW = 2; // Day of week = 0x03 = Wednesday
    RTCHOUR = 0; // Hour = 0x12
    RTCMIN = 0; // Minute = 0x57
    RTCSEC = 0; // Seconds = 0x36
    RTCCTL1 &= ~(RTCHOLD); // Start RTC calendar mode
    RTCCTL13 |= RTCLOCK;
    RTCCTL0_H = 0; // Lock RTC_C module
    PM5CTL0 &= ~LOCKLPM5;
    PMMCTL0_H = 0;

    And every boot up RTC configuration looks like below
    PMMCTL0_H = 0xA5;
    RTCCTL0_H = RTCKEY_H;
    RTCCTL0_L |= RTCRDYIE;
    RTCCTL1 |= RTCMODE;
    RTCCTL13 &= ~RTCHOLD;
    RTCCTL0_H = 0;
    PM5CTL0 &= ~LOCKLPM5;
    PMMCTL0_H = 0;

    Thank you all for help. See you soon!

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