4-to-1 Multiplexer

The entity mux4_1 has four data inputs (i_d0, i_d1, i_d2, i_d3) of type std_logic, a selector (i_sel) of type std_logic_vector(1 downto 0) and one output (o_q) of type std_logic.

When i_sel is "00", output o_q takes the value of i_d0. For "01" it is i_d1, for "10" it is i_d2, and for "11" it is i_d3. For any other value, the output is '0'.