Question

我已经写了一个通用的进位超前加法器的代码。但是我无法将此代码转换为包中的过程。有人可以帮我吗？

当我尝试编译此代码时，它没有将n注册为通用编号。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity Carry_Look_Ahead is

    Generic(n:integer:=4);

Port ( A : in STD_LOGIC_VECTOR (n-1 downto 0);
B : in STD_LOGIC_VECTOR (n-1 downto 0);
Cin : in STD_LOGIC;
S : out STD_LOGIC_VECTOR (n-1 downto 0);
Cout : out STD_LOGIC);
end Carry_Look_Ahead;

architecture Behavioral of Carry_Look_Ahead is

begin

process(A,B,Cin)

variable ci :STD_LOGIC_VECTOR(n downto 0);
variable P: STD_LOGIC_VECTOR(n-1 downto 0);
variable G: STD_LOGIC_VECTOR(n-1 downto 0);
variable si :STD_LOGIC_VECTOR(n-1 downto 0);     
          begin
       ci(0) := Cin;

FOR i IN 0 TO n-1 LOOP 

  P(i) := A(i) xor B(i);
  G(i) := A(i) and B(i);
  ci(i+1) := G(i) or (P(i) and G(i));
  si(i) := P(i) xor ci(i);

 END LOOP;
    S<=si;
    Cout<=ci(n);
end process;   

end Behavioral;

这是我尝试编译此代码时遇到的错误：

Unknown identifier "n".

Answer 1

子程序（如过程）可以具有通用参数。语法和用法类似于通用实体或通用包。

procedure cla
  generic (
    constant n  : in  positive
  )
  parameter (
    signal Cin    : in  STD_LOGIC;
    signal input1 : in  STD_LOGIC_VECTOR;
    signal input2 : in  STD_LOGIC_VECTOR;
    signal Sum    : out STD_LOGIC_VECTOR;
    signal Cout   : out STD_LOGIC
  ) is
  variable c : STD_LOGIC_VECTOR(n downto 0);
  variable P : STD_LOGIC_VECTOR(n-1 downto 0);
  variable G : STD_LOGIC_VECTOR(n-1 downto 0);
  variable s : STD_LOGIC_VECTOR(n-1 downto 0);  
begin
  c(0) := Cin;
  for i in 0 to n-1 loop
     P(i) := input1(i) xor input2(i);
     G(i) := input1(i) and input2(i);
     c(i+1) := G(i) or (P(i) and G(i));
     s(i) := P(i) xor c(i);
  end loop;
  Sum  <=s;
  Cout <=c(n);
end procedure;

Answer 2

我的朋友为此找到了解决方案：

您可以将整数用作通用数字。这是完成的PROCEDURE：

PROCEDURE cla (
      SIGNAL n               : IN  INTEGER; -- generic number
      SIGNAL Cin             : IN  STD_LOGIC;
      SIGNAL input1 , input2 : IN  STD_LOGIC_VECTOR;
      SIGNAL Sum             : OUT STD_LOGIC_VECTOR;
      SIGNAL Cout            : OUT STD_LOGIC
   ) IS
      VARIABLE c :STD_LOGIC_VECTOR(n downto 0);
      VARIABLE P: STD_LOGIC_VECTOR(n-1 DOWNTO 0);
      VARIABLE G: STD_LOGIC_VECTOR(n-1 DOWNTO 0);
      VARIABLE s :STD_LOGIC_VECTOR(n-1 DOWNTO 0);  
   BEGIN    
      c(0) := Cin;
      FOR i IN 0 TO n-1 LOOP 
         P(i) := input1(i) XOR input2(i);
         G(i) := input1(i) AND input2(i);
         c(i+1) := G(i) OR (P(i) AND G(i));
         s(i) := P(i) XOR c(i);
      END LOOP;
      Sum<=s;
      Cout<=c(n);
   END cla;

如何在VHDL中创建通用过程？

2 个答案: