Hi
As said above i am now using the idle mode during ADC conversion.
Now problem is my USB then stops working.
I am describing my firmware

main loop
{
If data is ready send the data using USB
}

Timer1 Interrupt after every 50uSeconds
{
Stop the timer
Start the ADC
IDLE mode (if this part is removed the whole firmware works)
}

ADC interrupt when conversion over and wakes up Microcontroller from idle mode
{
save the data to buffer
start the timer
}

According to datasheet the USB module is active in idle mode.But it is not able to send since when i remove the idle mode the firmware works perfectly.If somebody has worked on this please tell me what i am doing wrong.
Regards
Gopalakrishnan.Narayanan