I closed the earlier discussion as i thought the doubt is cleared. But still I am not able to figure out some problems.

I am using offset binary now. I am giving the data vector followed by zeros and some of the results that I am getting are -

Input Output
14'h0001 14'hFFFB
14'h0002 14'hFFF7
14'h0008 14'hFFDF
14'h20FA 14'h7C17
14'h1F05 14'h83EB

In the datasheet it is given that the BIST behaves as simple adder. So when giving this data it should have just returned the same data as result.

But in this case it looks like its just inverting the bits or XOR with 1. The two LSBs are 1 might be because of compatibility with AD9783.

Can you please verify that the output result what I am getting is correct or not ?