operation timing of single shot mode

kann jemand hier mir helfen bei programmierung da ads1015 in single shot 
mode statt in countiousl mode programmieren will.
ads1015 datashett lautet;
the ADS1015 wait until the OS bit is set high. Once asserted, the bit is 
set to '0', indicating that a conversion is currently in progress. Once 
conversion data are ready, the OS bit reasserts and the device powers 
down. Writing a '1'to the OS bit during a conversion has no effect.

in single-shot  mode:

uint16 read_ads( uint8 address )
{
uint16 analog_val ;

  analog_val = (int16)i2c_read( I2C_ADS1015, address, 1, ADSREG_CONV, 0, 
0 );

  if( analog_val < 0 )
    analog_val = 0 ;
  return( analog_val );
}

uint16 read_status(void)
{
tp_ads1015_config config_str;
uint16 config_reg ;
  return(config_str.os,0x0000);   // OS_RDY =1 WHEN CONVERSION  IN 
PROGRESS

}

void hal_adc_tick(void)

{
#ifdef I2C_ADC
static uint8  ad_ch ;
#endif
delay_10us(50);
  ADC12CTL0 |= ADC12SC;             // restart conversion


#ifdef I2C_ADC
start_ads( 0, 0 ) ;  // START CONVERSION
  while( ad_ch < (LENGTH( hal_adc ) -1 ))
    hal_adc[ad_ch+1] = read_status( ad_ch >> 2 ) ;

  ad_ch++ ;
return read_status(ad_ch >> 2 );        // Read out conversion result

  //if( ad_ch >= I2C_ADC )
    //ad_ch = 0 ;

  //start_ads( ad_ch >> 2, ad_ch ) ;
}
#endif