Send on a 8 data bus : 8 data and 8 data and ...

use counter and case, or 2D array:

type my_data is array(0 to 2) of std_logic_vector(7 downto 0);
signal my_characters: my_data := ("01110100","00001111","00110000");
 
-- or
--constant my_characters: my_data := ("01110100","00001111","00110000");
 
signal count: integer range 0 to 2;
 
begin
 
process
begin
wait until clk = '1';
 
if count = 2 then
    count <= 0;
else
    count <= count + 1;
end if;
 
bigbus <= my_characters(count);
 
end process;