VHDL：與選多個值

Question

我有以下代碼（它編碼的號碼的按下的按鈕的）：

with buttons select 
    tmp <= "000" when x"1", 
     "001" when x"2", 
     "010" when x"4", 
     "011" when x"8", 
     "100" when others; 
code <= input(1 downto 0); 
error <= input(2); 

我想重寫它，而無需使用tmp信號。可能嗎？以下不工作：

with buttons select 
    error & code <= "000" when x"1", 
        "001" when x"2", 
        "010" when x"4", 
        "011" when x"8", 
        "100" when others; 

Answer 1

，而不是與選擇，你可以使用情況：

my_process_name : process(buttons) 
begin 
    case buttons is 
    when x"1" => 
     error <= '0'; 
     code <= "00"; 
    when x"2" => 
     error <= '0'; 
     code <= "01"; 
    when x"4" => 
     error <= '0'; 
     code <= "10"; 
    when x"8" => 
     error <= '0'; 
     code <= "11"; 
    when others => 
     error <= '1'; 
     code <= "00"; 
    end case; 
end process;