Hi Shravan,
It is usually better to ask a new question on a new post to make sure your question gets answered. Old postings can get overlooked.
To answer your question, the data communcation cycle is 4 bytes. The first two bytes are the conversion results and the second two bytes are the configuration register settings. The least significant bit for the configuration register is always a '1', which means that the communication cycle ends with DOUT high. Using the pin as both DOUT and DRDY simply means that when the conversion cycle ends, the DOUT pin gets set low. So when you see the high to low transition, you know that the conversion is complete and the results are ready to be read out. You can see the behavior in Figure 45 of the ADS1118 datasheet. Also remember that CS must be low so that the DOUT/DRDY pin is not tri-state.
Best regards,
Bob B
