Please pay attention

Initialization code for RTC use

    // Enable the internal reference clock. MCGIRCLK is active.
    MCG->C1 |= MCG_C1_IRCLKEN_MASK;
    // Select the slow internal reference clock source.
    MCG->C2 &= ~(MCG_C2_IRCS_MASK);
    // Set PTC1 as RTC_CLKIN and select 32 KHz clock source for the RTC module.
    PORTC->PCR[1] &= ~PORT_PCR_MUX_MASK;
    PORTC->PCR[1] = PORT_PCR_MUX(1);    
    SIM->SOPT1 &= ~SIM_SOPT1_OSC32KSEL_MASK;
    SIM->SOPT1 |= SIM_SOPT1_OSC32KSEL(2);
    // Set PTC3 as CLKOUT pin and selects the MCGIRCLK clock to output on the CLKOUT pin.
    SIM->SOPT2 |= SIM_SOPT2_CLKOUTSEL(0x4);
    PORTC->PCR[3] |= (PORT_PCR_MUX(0x5));
    
    // enable RTC clock
    SIM->SCGC6 |= SIM_SCGC6_RTC_MASK;
    RTC->CR = RTC_CR_SWR_MASK;
    RTC->CR &= ~RTC_CR_SWR_MASK;
    
    if (RTC->SR & RTC_SR_TIF_MASK){
         RTC->TSR = 0x00000000;
    }    
    RTC->TCR = RTC_TCR_CIR(1) | RTC_TCR_TCR(0xFF);

    ecc...