CCS/MSP430F6435: Alarm wakeup interrupt for LPM3

Tool/software: Code Composer Studio

I am working on a small code which sets my controller (MSP430F6435), into sleep mode and get back in active mode by alarm interrupt. I referred to the sources but I am still missing on to something, the code never comes out of LPM3. I am attaching my code for referral

#include <stdio.h>
#include <msp430.h>

/*Sample code for testing the sleep mode(low power mode) of MSP430F6435 */

void Init_GPIO(void)
{
  // Port Configuration
  P1OUT = 0x00;P2OUT = 0x00;P3OUT = 0x00;P4OUT = 0x00;P5OUT = 0x00;P6OUT = 0x00;
  P7OUT = 0x00;P8OUT = 0x00;P9OUT = 0xFF;PJOUT = 0x00;
  P1DIR = 0xFF;P2DIR = 0xFF;P3DIR = 0xFF;P4DIR = 0xFF;P5DIR = 0xFF;P6DIR = 0xFF;
  P7DIR = 0xFF;P8DIR = 0xFF;P9DIR = 0xFF;PJDIR = 0xFF;
}

void init_RTC_B(void)       //NO PRESCALER USED
{

    UCSCTL6 &= ~(XT1OFF);                     // 32Khz capacitor used for MCLK, SMCLK, ACLK
    UCSCTL6 |= XCAP_3;                        // Internal load cap 12pF configuration
    while(BAKCTL & LOCKBAK)                   // Unlock XT1 pins for operation
       BAKCTL &= ~(LOCKBAK);
    do
    {
      UCSCTL7 &= ~(XT1LFOFFG + DCOFFG);
                                              // Clear XT1,DCO fault flags in case of possible faults that could set these registers high
      SFRIFG1 &= ~OFIFG;                      // Clear oscillator fault flags
    }while (SFRIFG1&OFIFG);                   // Till the oscillator fault flags are not cleared

    RTCCTL0 = RTCAIE;           //Alarm interrupt for wake up from low power mode
    RTCAMIN = 0x81;             //For 1 minute interupt

    RTCCTL1 = RTCHOLD;                        //Disables the calender mode

        RTCHOUR = 0x5;                        // Hour = 0x5
        RTCMIN = 0x6;                        // Minute = 0x15
        RTCSEC = 0x7;                        // Seconds = 0x25
}

void EnterLPM3(void)
{
  PMMCTL0_H = PMMPW_H;                      // Open PMM Registers for write
  PMMCTL0_L |= PMMREGOFF;                   // and set PMMREGOFF
  __bis_SR_register(LPM3_bits+ GIE);        // Enter LPM3.5 mode with interrupts//3.5 because minimum power consumption with backup RTC
  __no_operation();                         // enabled
}

#pragma vector=RTC_VECTOR
__interrupt void RTCISR (void)
{
  PMMCTL0_H = PMMPW_H;                      // open PMM
  PM5CTL0 &= ~LOCKLPM5;                     // Clear LOCKBAK and enable ports
  PMMCTL0_H = 0x00;                         // close PMM

  RTCCTL0 &= ~RTCAIE;
  __bic_SR_register_on_exit(LPM3_bits+ GIE);     // Exit LPM3
  __no_operation();
}

int main(void) {
    WDTCTL = WDTPW | WDTHOLD;	// Stop watchdog timer
    P5DIR |= BIT5;
    int i, sec;

    Init_GPIO();
    init_RTC_B();

    EnterLPM3();

    P5OUT |= 0X0020;
    while(1);
}

I am a newbie here and any help would be appreciable. Thank you.

Regards

-Onkar