Prasad.

Always the first question is : What do you see on the oscilloscope ? You should be able to see the clock lines ON THE ADC toggling, and the data line ON THE ADC responding. That is your sanity check.

Check too you have a valid reference voltage to the ADC, check you can apply a simple test voltage with a potentiometer.

Then see what happens on your processor pins.

Then start to look at the code. Check with the manufacturer's app notes that ALL the weird calibration of the device is completed by your code.

Steve