In Hibernate RTC Calendar mode Time Value leading from the expected Value at Power off.

Hello,

I am currently working on TM4C1294KCPDT , I have implemented internal RTC to work on both power ON as well as power OFF mode in Hibernate Calendar mode and Displaying its Value on ModScan 32 .

i used  a 3.3V Battery (BR2032) across the capacitor Connected to VBAT ( pin 68 ). 

Now my RTC is working properly in Power on but at power off condition my second Value Fluctuates i.e it Leads from the value expected.So whenever i check my RTC value after after power off it shows difference in some seconds that is Second value found to be more than expected.

my code is as follow:

//******************************************************************************************************

int main(void)

{

IntMasterDisable(); // Disable All IRQ

SysCtlPeripheralEnable(SYSCTL_PERIPH_HIBERNATE);

HibernateEnableExpClk(SYS_CLOCK);

HibernateClockConfig(HIBERNATE_OSC_LOWDRIVE);

HibernateRTCEnable();

HibernateCounterMode(HIBERNATE_COUNTER_24HR);

IntMasterEnable(); // Enable all IRQ

while(1)
{

if(gbiMbSlaveSer2)
{
gbiMbSlaveSer2 = 0; // Clear Modbus slave flag

if(!Modbus_Slave(&stSlaveSer2, &stMbSlaveSer2)) // Process the modbus packet
{
Ser2_Tx_Flush();

HibernateCalendarGet(&sTime);

Ser2_Write_Buff(stSlaveSer2.Response_Size);
Ser2_Start_Tx();
}
Ser2_Rx_Flush(); // Clear the Serial port 2 receive buffer
}

}

}

Can you Please let me know Why it is Happening and what is its solution.

Thanks

Vibha