How to add '0' to between every 2 bits of a logic vector

Question

Assume we have a 32 bit std_logic_vector of data. I want to add a logic '0' between every 2 bits. Take for example; all ones 11111....1111 is going to be 101010101....1010101.

Answer 1

You can add the '0' in between with a function:

function add_zeros(std_logic_vector_in : std_logic_vector) return std_logic_vector is
   variable std_logic_vector_out : std_logic_vector(std_logic_vector_in'length*2 -2 downto 0);
begin 
   for i in std_logic_vector_in'range loop
      std_logic_vector_out(i*2) := std_logic_vector_in(i);
      if (i /= std_logic_vector_in'length-1) then
         std_logic_vector_out(i*2+1) := '0';
      end if;
   end loop;
   return std_logic_vector_out;
end function;

For the final '0' you can add them with simple concatenation.

If you have:

signal initial_signal : std_logic_vector(31 downto 0);
signal final_signal   : std_logic_vector(66 downto 0);

Then you can just write:

final_signal   <= '0' & '0' & '0' & '0' & add_zeros(initial_signal);