// I have initialized PORTB like this

PORTB=0x00;
DDRB=0xBF;

// SPI initialisation
// SPI clock rate fck/16
// SPI master
// SPI MSB first
// SPI CPOL = 1, CPHA = 1

SPCR=0x5D;
PORTB.3 = 1;

void main (void){

 printf("adc value :%xn",ReadAd());

}

#define ADC_CS PORTB.3
#define WG_CS PORTB.4
#define MOSI PORTB.5
#define MISO PINB.6
#define SCK PORTB.7

#define ADC_CS_PIN PINB.3
#define WG_CS_PIN PINB.4

char spi(char data)
 {
//Start transmision
SPDR = data;
//Wait for transmision complete
while(!(SPSR & 0x80));
return SPDR;
 }

//Sets the waveform generator output to given phase
void SetWGPhase(unsigned int phase)
 {
SPCR = 0x5A;
WG_CS = 0;
while(WG_CS_PIN);
spi(0x20);
spi(0x00);
spi((char)((phase>>8)|0xC0));     //Load into phase register 0
spi((char)(phase & 0x00FF));
WG_CS = 1;
}

unsigned int ReadAd(void)
{
unsigned int data;
 ChipSelectAd(1);
//Read data
CheckStatus();         //Wait for data ready in
                         adc register
spi(0x58);              //Place readinstruction
                        in communication register
data = (spi(0xFF)<<8);    //Read 8 most significant
                         bits from data register
data |= spi(0xFF);      //Read 8 leastsignificant
                         bits from data register
return data;

ChipSelectAd(0);
}

void CheckStatus(void)
{
char adcStatus;

do
{
(void) spi(0x40);
adcStatus = spi(0xFF);
} while((adcStatus & 0x80) > 0);
}

void ChipSelectAd(char s)
{
if(s == 1){
    PORTB.3 = 0;    //Switch on AD
    while(PINB.3);  //Wait for chip select pin
}
    else
        PORTB.3 = 1;    //Switch of AD
 }