Примерно так
Код
while(1)
{
SystemTime.tm_sec = RTCREG_SEC;
SystemTime.tm_min = RTCREG_MIN;
SystemTime.tm_hour = RTCREG_HOUR;
SystemTime.tm_mday = RTCREG_DOM;
SystemTime.tm_mon = RTCREG_MONTH - 1;
SystemTime.tm_year = RTCREG_YEAR - 1900;
SystemTime.tm_wday = RTCREG_DOW;
SystemTime.tm_yday = RTCREG_DOY;
SystemTime.tm_isdst = -1;
// Check for time and data change
if(RTCREG_SEC == SystemTime.tm_sec)
break;
}