Could not find the output of ADC even succesfully debugged adn have run it msp430f6638

 Hello everyone,

Im a beginner to msp430  and ccs v4 so please pardon my knowledge if i did not understand or ask basic concepts.

I am trying to execute ADC project in ccs v4 using MSP430F6638IPZR kit with a  MSP430 USB-Debug-Interface MSP-FET430UIF. the maximum software configurable supply voltage that this USB-Debug-Interface can handle is between 1.8 V to 3.6 V at 100 mA.

I am trying to execute a ADC project  in which as it says converts analog to digital output.

i will have to give 2.5V as input to the msp430f6638 target. when i read the data sheet it is shown that AVcc and Avss pins are pin 11 and pin 12. following is

the snapshot of pin configuration.

and my code is 

#include <msp430f6638.h>

void main(void)
{
volatile unsigned int i;
WDTCTL = WDTPW+WDTHOLD;                                   // Stop watchdog timer
P6SEL |= 0x01;                                                                        // Enable A/D channel A0
REFCTL0 &= ~REFMSTR;                                               // Reset REFMSTR to hand over control to
                                                                                              // ADC12_A ref control registers
ADC12CTL0 = ADC12ON+ADC12SHT02+ADC12REFON+ADC12REF2_5V;
                                                                                              // Turn on ADC12, Sampling time
                                                                                          // On Reference Generator and set to
                                                                                          // 2.5V
ADC12CTL1 = ADC12SHP;                                       // Use sampling timer
ADC12MCTL0 = ADC12SREF_1;                             // Vr+=Vref+ and Vr-=AVss

for ( i=0; i<0x30; i++);                                                   // Delay for reference start-up

ADC12CTL0 |= ADC12ENC;                                     // Enable conversions

while (1)
{
ADC12CTL0 |= ADC12SC;                                        // Start conversion
while (!(ADC12IFG & BIT0));
__no_operation();                                                       // SET BREAKPOINT HERE

}
}

when i gave the input voltage at pins 11 and 12 target board of 2.5 V i could not see any out put in ADC12MEM0.

did i give the input voltage to the right pins? If not to which pins should i give the input voltage.

Is output is displayed in ADC12MEM0 or some other place.

what is microcontroller reference voltage?

It would be very much helpful if anyone got me through this problem as i have been facing it from long time.

Thanks in advance.