ADS1255 data reading problem

Dear Friends,

I am using ADS1255 with ATmega32. I am using linux OS and GCC compiler for this purpose. I am right now using single shot mode acoording to datasheet.

Now what my problem is, I am getting DRDY pin change but after RDATA command I am not getting data on Dout pin.

My command sequence is as follows:

First i m sending WAKEUP command .... ads1255 responds to it and DRDY signal goes low ... after that i send RDATA command and wait for data on DOUT line. But no data is outputed on Dout pin.

I am using all default settings, i.e: fdata = 30ksps, all default values in registers, no mux, AVdd = 5v, DVdd = 3.3v, VrefP = 2.5v, VinP = +5v and VinN = Gnd. My connections of Ads1255 are exactly as shown in Datasheet of ads1255 pg.28 fig.25. SCLK = 2Mhz.

code:

SIGNAL(SIG_INTERRUPT2) // from drdy'
{
// This is DRDY' event go high - SYNC
// transmit sync command @ MOSI
PORTB = (0<<PB4);
_delay_ms(1);
SPDR = 0xFC;
while(!(SPSR & (1<<SPIF)));
PORTB = (1<<PB4);
}

SIGNAL(SIG_INTERRUPT0) // from drdy'
{
// This is DRDY' event
// transmit command @ MOSI
PORTB = (0<<PB4);
 _delay_ms(1);
SPDR = 0x01;
while(!(SPSR & (1<<SPIF)));
PORTB = (1<<PB4);
}

SIGNAL(SIG_INTERRUPT1)  // ext interrupt
{
// This is external event
// transmit command @ MOSI
PORTB = (0<<PB4);
 _delay_ms(1);
SPDR = 0xff;
while(!(SPSR & (1<<SPIF)));
PORTB = (1<<PB4);
}

int main(void)
{
// initialization of spi
DDRB = (1<<DDB4)|(1<<DDB5)|(1<<DDB7);
SPCR = (1<<SPE)|(1<<MSTR)|(1<<CPHA);
SPSR = (1<<SPI2X);
PORTB = (1<<PB4);
//initialize ext int0 and int1
DDRD = (0<<INT0)|(0<<INT1); //making sure int0 is input
DDRB = (0<<INT2);
MCUCR = (1<<ISC01)|(1<<ISC11); //interupt on falling edge of
MCUCSR = (1<<ISC2);
GICR = (1<<INT0)|(1<<INT1)|(1<<INT2);

sei();
for(;;)
{}
return 0;
}