Compiler/MSP430FR6989: Real Time Clock interrupt clarification.

Hi Andy,
sorry, but it is not perfectly clear, which kind of configuration and code you're applying to your setup. Thus, to avoid unnecessary efforts, could you please strip the code down to the RTC functionality only, and post it?
If you do not want to disclose the code here, please let me know. There are ways to share it privately through the forum.
Many thanks in advance.

Best regards
Peter

Thanks for responding, Peter. I dont have anything proprietary its just that I like to put the 'under the hood' stuff in subroutines in the header file and was a bit lazy about rearranging them in an appropriate format for this forum. No prob though. Note the questions are annotated below. I've done quite a bit of searching but havent found anything to date so am asking you guys. 

#include "driverlib.h"
#include "rtc_c.h"

#define ONE_SECOND 8000000
#define HALF_SECOND 4000000
#define LF_CRYSTAL_FREQUENCY_IN_HZ 32768

/************************************************* prototypes*****************************

******************************************************************************************/
/***** Defines ***************************************************************/

#define ONE_SECOND 8000000
#define HALF_SECOND 4000000
#define LF_CRYSTAL_FREQUENCY_IN_HZ 32768
#define XT_TIMEOUT 100000
#define GPIO_ALL GPIO_PIN0|GPIO_PIN1|GPIO_PIN2|GPIO_PIN3| \
GPIO_PIN4|GPIO_PIN5|GPIO_PIN6|GPIO_PIN7

/******************************************************************************************/
/************************************************* Global Variables ************************/

RTC_C_configureCalendarAlarmParam alarmParam;
Calendar currentTime;
bool bReturn = STATUS_FAIL;

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

int main(void)
{
WDTCTL = WDTPW | WDTHOLD; // stop watchdog timer

//init LFXtl********************************************************************
GPIO_setAsInputPinWithPullDownResistor(GPIO_PORT_PJ, GPIO_ALL);
PMM_unlockLPM5();
GPIO_setAsPeripheralModuleFunctionInputPin(
GPIO_PORT_PJ,
GPIO_PIN4 + // LFXIN on PJ.4
GPIO_PIN5 , // LFXOUT on PJ.5
GPIO_PRIMARY_MODULE_FUNCTION);

CS_setExternalClockSource (32768,0);
bReturn = CS_turnOnLFXTWithTimeout(
CS_LFXT_DRIVE_0,
XT_TIMEOUT
);

if ( bReturn == STATUS_FAIL )
{
while( 1 );
}

//init Real Time Clock
currentTime.Seconds = 0x00;
currentTime.Minutes = 0x26;
currentTime.Hours = 0x13;
currentTime.DayOfWeek = 0x03;
currentTime.DayOfMonth = 0x20;
currentTime.Month = 0x07;
currentTime.Year = 0x2011;
RTC_C_initCalendar(RTC_C_BASE,&currentTime,RTC_C_FORMAT_BCD);

// set alarm for one minute later to test
alarmParam.minutesAlarm = 0x27;
alarmParam.hoursAlarm = 0x13;
alarmParam.dayOfWeekAlarm = RTC_C_ALARMCONDITION_OFF;
alarmParam.dayOfMonthAlarm = RTC_C_ALARMCONDITION_OFF;
RTC_C_configureCalendarAlarm(RTC_C_BASE,&alarmParam);

//Question: Is this a necessary step if I just want a one time alarm interrupt?
RTC_C_setCalendarEvent(RTC_C_BASE,RTC_C_CALENDAREVENT_MINUTECHANGE);
//

// Clearing interrupts just to be sure

// Question: is there a better method to do this? Seems redundant.
RTC_C_clearInterrupt(RTC_C_BASE,
RTC_C_CLOCK_READ_READY_INTERRUPT +
RTC_C_TIME_EVENT_INTERRUPT +
RTC_C_CLOCK_ALARM_INTERRUPT);

// now enabling

//Question: Are the Read ready interrupt and time event interrupt enables always necessary?
// I would think the alarm interrupt would include the read ready (and not sure why the time event is there).

RTC_C_enableInterrupt(RTC_C_BASE,
RTC_C_CLOCK_READ_READY_INTERRUPT +
RTC_C_TIME_EVENT_INTERRUPT +
RTC_C_CLOCK_ALARM_INTERRUPT);

RTC_C_startClock(RTC_C_BASE);

__bis_SR_register(LPM3_bits + GIE);// enable interrupt and go to LPM3

return 0;
}

char i2; // included to give vectors a place to break while debugging

#pragma vector = RTC_VECTOR
__interrupt void TimerRTC_ISR(void)
{
switch(__even_in_range(RTCIV,16))
{
case 0: break; // No interrupts
case 2: // RTCRDYIFG
i2=1;
break;

// Question: Interrupts here at ~ 1 sec interval. Why wake mpu if not needed - even for a very short time?
case 4: // RTCEVIFG - interrupt on prescale interval timer
i2=1;
break;

// Interrupts here as expected
case 6: // RTCAIFG Clock alarm flag. Remains cleared when in counter mode
i2=1;
break;

// Doesnt interrupt here that I have found, as expected.

case 8: // RT0PSIFG
i2=1;
break;

// Question: Interrupts here if I only enable alarm interrupt but not the other two - why that behavior?
case 10: // RT1PSIFG
i2=1;
break;

case 12: break; // Reserved
case 14: break; // Reserved
case 16: break; // Reserved
default: break;
}

return; // No wakeup

}
/*
* RTCRDYIFG -> interrupt on the rising edge of TRCRd:Y bit you have one second to access reg values
* RTCEVIFG -> interrupt on prescale interval timer
* RTCAIFG -> Calender (min,hrs,dayof month, day of week) alarm flag. Remains cleared when in counter mode
* RT0PSIFG -> genned when prescale returns to 0
* RT1PS -> genned on preset divide by 2,4,88,16,32,64,128, or 256
*/

Hi Andy,
many thanks for the clarification.
Let's start with the RTCRDYIFG: No, for a configured alarm and operation without accessing the RTC_C control registers, this interrupt would not be necessary. The important point about the RTCRDYIFG is the following. The RTC_C is usually running asynchronously to the CPU and the rest of the system, as these are clocked usually by other clocks. Thus there could be a collision between the RTC_C logic accessing and updating the RTC_C registers and e.g. the CPU accessing and modifying those. This could lead to erroneous results. Thus it is necessary to avoid such collisions. This is the purpose of the RTCRDYIFG, as it tells the CPU, when it is safe accessing the RTC_C registers. If you have already configured the RTC_C and reached a steady operating state, and not accessing the RTC_C registers at all, you can shut the RTCRDYIFG off.
For a pure alarm interrupt, also the RTCEVIE is not necessary. This event interrupt flag can be used to obtain triggers from the RTC_C in a regular time frame, e.g. minute, hour, midnight, noon. If you do not need this, you can switch this off.

//Question: Is this a necessary step if I just want a one time alarm interrupt?
RTC_C_setCalendarEvent(RTC_C_BASE,RTC_C_CALENDAREVENT_MINUTECHANGE);
//
As mentioned, this is not necessary. I think the intention of the author of the driver lib was to showcase "everything" in one code example.

// Question: Interrupts here at ~ 1 sec interval. Why wake mpu if not needed - even for a very short time?
No, if not needed, it definitely makes no sense.

// Question: Interrupts here if I only enable alarm interrupt but not the other two - why that behavior? RT1PSIFG
Need to check on this, why it occurs in your case. This should only happen when RT1PSIE is enabled.

Best regards
Peter

Errr.. One more comment (embarrassed). It turns out that the
RTC_C_clearInterrupt(RTC_C_BASE,
RTC_C_CLOCK_READ_READY_INTERRUPT +
RTC_C_TIME_EVENT_INTERRUPT +
RTC_C_CLOCK_ALARM_INTERRUPT);
in the driverlib doesnt clear everything (check the documentation). That is why I was getting a 1 sec interrupt.