Hi Shravan,
If you are seeing a lot of digital crosstalk, you probably are seeing a grounding problem. If you are not using a PCB, but rather a prototyping system such as solderless breadboard, then noise can greatly interfere with the signals.
Also remember that the configuration register writes requires that certain bits follow a particular pattern. Notice on page 22 of the ADS1118 datasheet that Bits[2:1] must follow the pattern '01' for a valid update to the Config register.
I've shown a picture below that shows how to create a new post. You must go to the main forum page of the forum you wish to post in and then you will see the button for New Post in the upper right corner of the page. I have circled it in green in the picture.
Best regards,
Bob B