VHDL program doesn' t compile

Question

I am trying to create a VHDL ALU with structural way that does the following operations: 1)ADDITION 2)SUBSTRACTION 3)LOGIC AND 4)LOGIC OR

I'm running my code in Quartus II and it finds some errors at compilation. Here is my code :

library ieee;
use ieee.std_logic_1164.all;
use work.basic_func.all;

entity askhsh1 is
port
(   a : in std_logic_vector(15 downto 0);
    b : in std_logic_vector(15 downto 0);
    coin : in std_logic;
    coout : out std_logic;
    s : in std_logic_vector(15 downto 0);
    d : in std_logic_vector(15 downto 0);
    result : out std_logic;
    operator : in std_logic;
    binvert : in std_logic;
    ainvert : in std_logic);

 end askhsh1;

 architecture structure of askhsh1 is 
    signal c : std_logic_vector(1 to 15);
    signal result : std_logic_vector(15 downto 0);
 component myAND
    port (in1, in2: in std_logic; out1: out std_logic);
end component;
component myOR
    port (in1, in2: in std_logic; out1: out std_logic);
end component;
component myXOR
    port (in1, in2: in std_logic; out1: out std_logic);
end component;
component fullader
    port (cin, x, y : in std_logic; 
            s, cout : out std_logic);
end component;
begin 
U1 : myAND port map (a, b, result) when (operator = '0') else T1 : myOR port map (a, b, result) when (operator = '1')
else (stage0 : fullader port map (coin, a(0), b(0), s(0), c(1));
       stage1 : fullader port map (c(1), a(1), b(1), s(1), c(2));
        stage2 : fullader port map (c(2), a(2), b(2), s(2), c(3));
        stage3 : fullader port map (c(3), a(3), b(3), s(3), c(4));
        stage4 : fullader port map (c(4), a(4), b(4), s(4), c(5));
        stage5 : fullader port map (c(5), a(5), b(5), s(5), c(6));
        stage6 : fullader port map (c(6), a(6), b(6), s(6), c(7));
        stage7 : fullader port map (c(7), a(7), b(7), s(7), c(8));
        stage8 : fullader port map (c(8), a(8), b(8), s(8), c(9));
        stage9 : fullader port map (c(9), a(9), b(9), s(9), c(10));
        stage10 : fullader port map (c(10), a(10), b(10), s(10), c(11));
        stage11 : fullader port map (c(11), a(11), b(11), s(11), c(12));
        stage12 : fullader port map (c(12), a(12), b(12), s(12), c(13));
        stage13 : fullader port map (c(13), a(13), b(13), s(13), c(14));
        stage14 : fullader port map (c(14), a(14), b(14), s(14), c(15));
        stage15 : fullader port map (c(15), a(15), b(15), s(15), coout);) when (operator = '2' and binvert = '0' and ainvert = '0')

else  (stage0 : fullader port map ('1', a(0), not b(0), s(0), c(1));
       stage1 : fullader port map (c(1), a(1), not b(1), s(1), c(2));
        stage2 : fullader port map (c(2), a(2), not b(2), s(2), c(3));
        stage3 : fullader port map (c(3), a(3), not b(3), s(3), c(4));
        stage4 : fullader port map (c(4), a(4), not b(4), s(4), c(5));
        stage5 : fullader port map (c(5), a(5), not b(5), s(5), c(6));
        stage6 : fullader port map (c(6), a(6), not b(6), s(6), c(7));
        stage7 : fullader port map (c(7), a(7), not b(7), s(7), c(8));
        stage8 : fullader port map (c(8), a(8), not b(8), s(8), c(9));
        stage9 : fullader port map (c(9), a(9), not b(9), s(9), c(10));
        stage10 : fullader port map (c(10), a(10), not b(10), s(10), c(11));
        stage11 : fullader port map (c(11), a(11), not b(11), s(11), c(12));
        stage12 : fullader port map (c(12), a(12), not b(12), s(12), c(13));
        stage13 : fullader port map (c(13), a(13), not b(13), s(13), c(14));
        stage14 : fullader port map (c(14), a(14), not b(14), s(14), c(15));
        stage15 : fullader port map (c(15), a(15), not b(15), s(15), coout);) when (operator = '2' and binvert = '1' and ainvert = '0')

else (stage0 : fullader port map ('1', not a(0), b(0), s(0), c(1));
       stage1 : fullader port map (c(1), not a(1), b(1), s(1), c(2));
        stage2 : fullader port map (c(2), not a(2), b(2), s(2), c(3));
        stage3 : fullader port map (c(3), not a(3), b(3), s(3), c(4));
        stage4 : fullader port map (c(4), not a(4), b(4), s(4), c(5));
        stage5 : fullader port map (c(5), not a(5), b(5), s(5), c(6));
        stage6 : fullader port map (c(6), not a(6), b(6), s(6), c(7));
        stage7 : fullader port map (c(7), not a(7), b(7), s(7), c(8));
        stage8 : fullader port map (c(8), not a(8), b(8), s(8), c(9));
        stage9 : fullader port map (c(9), not a(9), b(9), s(9), c(10));
        stage10 : fullader port map (c(10), not a(10), b(10), s(10), c(11));
        stage11 : fullader port map (c(11), not a(11), b(11), s(11), c(12));
        stage12 : fullader port map (c(12), not a(12), b(12), s(12), c(13));
        stage13 : fullader port map (c(13), not a(13), b(13), s(13), c(14));
        stage14 : fullader port map (c(14), not a(14), b(14), s(14), c(15));
        stage15 : fullader port map (c(15), not a(15), b(15), s(15),        coout);) when (operator = '2' and ainvert = '1' and binvert = '0')
else P1 : myXOR port map (a, b, result) when (operator = '3');
end structure;

The package basic_func is here:

 library ieee;
 use ieee.std_logic_1164.all;

 package basic_func is 
component myAND
    port (in1, in2: in std_logic; out1: out std_logic);
end component;
component myOR
    port (in1, in2: in std_logic; out1: out std_logic);
end component;
component myXOR
    port (in1, in2: in std_logic; out1: out std_logic);
end component;
component fullader
    port (cin, x, y : in std_logic; 
            s, cout : out std_logic);
end component;
end package basic_func;


  library ieee;
  use ieee.std_logic_1164.all;
  entity myAND is
port (in1, in2: in std_logic; out1: out std_logic);
end myAND;
  architecture modeland of myAND is
begin
    out1 <= in1 and in2;
  end modeland;


  library ieee;
  use ieee.std_logic_1164.all;
  entity myOR is
  port (in1, in2: in std_logic; out1: out std_logic);
  end myOR;
  architecture modelor of myOR is
begin
    out1 <= in1 or in2;
    end modelor;


   library ieee;
   use ieee.std_logic_1164.all;
   entity myXOR is
   port (in1, in2: in std_logic; out1: out std_logic);
   end myXOR;
   architecture modelxor of myXOR is
   begin
     out1 <= in1 xor in2;
   end modelxor;


   library ieee;
   use ieee.std_logic_1164.all;
   entity myfullader is
   port (cin, x, y : in std_logic; 
            s, cout : out std_logic);
   end myfullader;
  architecture modelfulla of myfullader is
   begin
     s <= x xor y xor cin;
     cout <= (x and y) or (cin and x) or (cin and y);
   end modelfulla;

Any help is appreciated

Answer 1

Your approach to the problem of selecting the different outputs of the functional blocks (addition, etc) is not valid:

U1 : myAND port map (a, b, result) when (operator = '0') else T1 : myOR port map (a, b, result) when (operator = '1') -- and so on

Remember that you are describing hardware. What you have attempted to do here is to instantiate different hardware, depending on the operator, which changes during run time. What you need to do is to instantiate all the functional blocks, then use your operator to multiplex the output of one of those functional blocks to your output. It's difficult to give an example you can copy exactly, but the general way to select one of the outputs would look something like this (where operator is an integer range 0 to 2):

process (operator, adder_output, and_output, or_output) 
begin
  case (operator) is
    when 0 => result <= and_output;
    when 1 => result <= or_output;
    when 2 => result <= adder_output;
  end case;
end process;

There are a few other points to make.

1. Your operator is defined as an std_logic, and you are trying to check for it being '2'. It looks like to implement the number of operators you have, you should define this input to be an integer. Having done this, you test this input against an integer literal, which would look like 2, not '2'. I would make the input operator : in integer range 0 to 2, assuming you have 3 operators.

2. You have result defined as an std_logic port, and an std_logic_vector signal. It is not clear what you actually wanted, but I suspect you should make your result port an std_logic_vector, and remove the signal.

3. You are instantiating entities using positional association. this is not generally recommended. Where you have:

   stage0 : fullader port map (coin, a(0), b(0), s(0), c(1));
   

   You would instead use named association:

   stage0 : fullader port map (
     cin => coin,
     x => a(0),
     y => b(0),
     s => s(0),
     cout => c(1)
   );
   

   This prevents bugs if somebody alters the port list, and makes the code more readable.

4. I would suggest making the code more structured, so that you create an entity that creates an 8-bit adder using your fulladder entites, then you can much more cleanly instnatiate this one 8-bit adder in your top level. This will make it more clear in your code what is going on.

5. If you did have a need to conditionally instantiate an entity, you would use the generate statement:

   SomeLabel : if (my_condition = true) generate
     stage0 : fullader port map (
       cin => coin,
       x => a(0),
       y => b(0),
       s => s(0),
       cout => c(1)
     );
   end generate;
   

   Again, I don't think this is what you should be using in this case, as generate is a compile-time construct, and you want the behavior to change during run-time.