MSP432 RTC example

hy guys I start work with the RTC module and therefore I tested the code of the TI side (see below).

//******************************************************************************
//  MSP432P401 Demo - RTC in real time clock mode
//
//  Description: This program demonstrates the RTC mode by triggering the event
//  interrupt RTCRDYIE event, which triggers every minute change. P1.1 toggles
//  every minute to indicate this interrupt.
//  After configuring the RTC, device goes into LPM3 and waits for the RTC interrupts.
//  Notice that RTC starting second is set to be 45, so after starting the program
//  the first RTC interrupt should trigger after ~15 seconds. Consequent interrupts
//  should occur every minute.
//  This code recommends an external LFXT1 crystal for RTC accuracy.
//  ACLK = LFXT1 = 32768Hz, MCLK = SMCLK = default DCO = 32 x ACLK = 1048576Hz
//
//                MSP432p401rpz
//             -----------------
//        /|\ |              XIN|-
//         |  |                 | 32kHz
//         ---|RST          XOUT|-
//            |                 |
//            |            P1.0 |--> Toggles every minute
//            |                 |
//
//
//   Dung Dang
//   Texas Instruments Inc.
//   November 2013
//   Built with Code Composer Studio V6.0
//******************************************************************************
#include "msp.h"

int main(void)
{
    WDTCTL = WDTPW | WDTHOLD;               // Stop WDT

    /* Configure P1.0 LED */
    P1DIR |= BIT0 ;
    P1OUT &= ~( BIT0 );


    // Configure RTC
    RTCCTL0_H = RTCKEY_H ;                 // Unlock RTC key protected registers
    RTCCTL0_L |= RTCTEVIE ;
    RTCCTL0_L &= ~(RTCTEVIFG);
    RTCCTL1 = RTCBCD | RTCHOLD ;
    // RTC enable, BCD mode, RTC hold
    // enable RTC read ready interrupt
    // enable RTC time event interrupt

    RTCYEAR = 0x2010;                         // Year = 0x2010
    RTCMON = 0x4;                             // Month = 0x04 = April
    RTCDAY = 0x05;                            // Day = 0x05 = 5th
    RTCDOW = 0x01;                            // Day of week = 0x01 = Monday
    RTCHOUR = 0x10;                           // Hour = 0x10
    RTCMIN = 0x32;                            // Minute = 0x32
    RTCSEC = 0x45;                            // Seconds = 0x45

    RTCADOWDAY = 0x2;                         // RTC Day of week alarm = 0x2
    RTCADAY = 0x20;                           // RTC Day Alarm = 0x20
    RTCAHOUR = 0x10;                          // RTC Hour Alarm
    RTCAMIN = 0x23;                           // RTC Minute Alarm

    RTCCTL1 &= ~(RTCHOLD);                    // Start RTC calendar mode

    RTCCTL0_H = 0;                            // Lock the RTC registers


    /* Enable all SRAM bank retentions prior to going to LPM3 (Deep-sleep) */
    SYSCTL_SRAM_BANKRET |= SYSCTL_SRAM_BANKRET_BNK7_RET;

    __enable_interrupt();
    NVIC_ISER0 = 1 << ((INT_RTC_C - 16) & 31);


    SCB_SCR |= SCB_SCR_SLEEPONEXIT;        // Sleep on exit from ISR

      while (1)
      {

          /* Setting the sleep deep bit */
          SCB_SCR |= (SCB_SCR_SLEEPDEEP);

          __sleep();


          /* Clearing the sleep deep bit */
          SCB_SCR &= ~(SCB_SCR_SLEEPDEEP);

      }

}

// RTC interrupt service routine

void RtcIsrHandler(void)
{

    if (RTCCTL0 & RTCTEVIFG)
    {
        P1OUT ^= BIT0;
        RTCCTL0_H = RTCKEY_H ;
        RTCCTL0_L &= ~RTCTEVIFG;
        RTCCTL0_H = 0;
    }

}

All works great, but I don't understand how the interrupt got called every minute when the RTCAMIN register was set to 0x23 (23) and not 1. 

Maybe anyone can help me ?