NXP Semiconductors Kinetis KE1xZ256, Reference Manual

Page: 1087 / 1325

RTC Module Initialization
The RTC module is reset by a POR or a software reset (The access control registers are
not affected by either VBAT POR or the software reset).
Before using the RTC module, a software reset is recommend by setting the
RTC_CR[SWR] bit. And the 32.768 kHz external crystal should be enabled to provide
clock to RTC.
// Reset the RTC by set RTC_CR[SWR] bit, and wait
// for the TIF flag cleared by writing the TSR
while (RTC_SR & RTC_SR_TIF_MASK)
{
RTC_CR |= RTC_CR_SWR_MASK;
RTC_CR &= ~RTC_CR_SWR_MASK;
RTC_TSR = 1;
}
// Setup the update mode and supervisor access mode
// enable 32.768 kHz oscillator timer
RTC_CR = RTC_CR_CPE(0) | RTC_CR_LPOS(0) | RTC_CR_CPS(1) |
RTC_CR_UM(0) | RTC_CR_SUP(0)| RTC_CR_OSCE(1);
// disable all the interrupts first
RTC_IER = 0;
// stop timer first
RTC_SR &= ~RTC_SR_TCE_MASK;
Set Date Time
After RTC initialized, user can set the date time before starting the timer. Please make
sure the timer is stopped when setting the date time by RTC_TSR register.
// stop timer first
RTC_SR &= ~RTC_SR_TCE_MASK;
// convert the date time to secs first, then write to RTC_TSR register
RTC_TSR = datetime_in_secs;
// start the timer
RTC_SR |= RTC_SR_TCE_MASK;
Set Alarm
To set an alarm and trigger alarm interrupt, user should enable the alarm interrupt, write
the alarm seconds into RTC_TAR.
uint32_t datetime_in_secs;
// assume the timer is running
// enable the interrupt
RTC_IER |= RTC_IER_TAIE_MASK;
// enable the RTC IRQ in NVIC
NVIC_EnableIRQ(RTC_IRQn);
// get the current date time in secs
datetime_in_secs = RTC_TSR;
datatime_i= 10;
// set alarm 10s later
RTC_TAR = datetime_in_secs;
After 10 seconds, the RTC Alarm IRQ would be triggered and IRQ Handler called. In the
IRQ Handler, user should first clear the interrupt status:
Chapter 43 Real Time Clock (SRTC)
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
NXP Semiconductors 1087