The sine and cosine output fields are sign extended to the next byte boundary
then concatenated, with cosine in the least significant portion, to create
m_axis_data_tdata. If only one of sine or cosine is selected, it is
sign extended and put into the least significant portion of
m_axis_data_tdata.
The following figure shows the internal structure of TDATA for the three
configurations: quadrature outputs, cosine only, and sine only. An 11-bit output has
been shown in the diagram for example, sign extended to 16 bits. The <<<
denotes sign extension.