Select the options for the direction of the channel that the Aurora 64B/66B core
supports. Simplex cores have a single, unidirectional serial port that connects to a
complementary simplex core. Three simplex options are provided to select the channel
direction supported by the core: RX-only_simplex,
TX-only_simplex or TX/RX_simplex.
Duplex or TX/RX_simplex
specify that the core has both TX and the corresponding RX communication channels.
Default: Duplex