ADS1231: ADS1231 only return 0x800000

Hello,

I don't understand what is going wrong. When the data line is ready I read 24 bits, but the value is always the same: 0x800000.

I enable AVDD voltage, wait 2 seconds to make sure voltage is okay, and wait 15useconds between measure and measure because od the update time.

Why am I getting this value??

This is my code:

void ads1231_on()
{
    DO_PIN_AVDD     = 1;     // Enable AVDD
    DO_PIN_ADS_PDWN = 0;

    __delay_ms(2000);
    
    DO_PIN_ADS_PDWN  = 1;  // Enable ADS1231
    DO_PIN_ADS_CLOCK = 0;
}

void ads1231_off()
{
    DO_PIN_AVDD     = 0;   
    DO_PIN_ADS_PDWN = 0;
}

int24_t ads1231_read()
{
    int24_t data      = 0;
    int24_t tmp       = 0;
    int8_t bit_shift;
    
    // Wait the IC to be ready
    while( (DI_PIN_ADS_DATA)==1 ){};
    __delay_us(100);

    // Read data
    for(bit_shift=23; bit_shift >= 0; bit_shift--)
    {  
        DO_PIN_ADS_CLOCK = 1;
        __delay_ns(200);
        
        tmp =  DI_PIN_ADS_DATA;
        tmp = (tmp << bit_shift);
        data |= tmp;  

        
        DO_PIN_ADS_CLOCK = 0;
        __delay_ns(200);

    }
 
    // Send Final clock signal to end transmition
    DO_PIN_ADS_CLOCK = 1;
    __delay_ns(200);
    DO_PIN_ADS_CLOCK = 0;
    __delay_ns(200);

    return data;
}

void main(void)
{
    setup();  // Setup IO
    
    int24_t value1;
    int24_t value2;
    int24_t value3;
    int24_t value4;
    int24_t value5;
    int24_t value6;
    int24_t value7;

    ads1231_on();

    while(1)
    {
        
        value1 = ads1231_read();
            __delay_us(15);

        value2 = ads1231_read();
            __delay_us(15);

        value3 = ads1231_read();
            __delay_us(15);

        value4 = ads1231_read();
            __delay_us(15);

        value5 = ads1231_read();
            __delay_us(15);

        value6 = ads1231_read();
            __delay_us(15);

        value7 = ads1231_read();
    __delay_us(15);


    }


}

Thank you!