用VHDL设计全减器的VHDL。要求: 首先设计半减器,然后用例化语句将它们连接起来,图3-18中h_suber是半减器,diff是输出差,s_out是借位输出,sub_in是借位输入。
时间: 2024-03-25 19:38:45 浏览: 109
下面是用VHDL设计全减器的代码:
```vhdl
-- 定义半减器
entity h_suber is
Port ( a : in STD_LOGIC;
b : in STD_LOGIC;
diff : out STD_LOGIC;
s_out : out STD_LOGIC);
end h_suber;
architecture Behavioral of h_suber is
begin
diff <= a xor b; -- 异或运算实现差
s_out <= not a and b; -- 与非运算实现借位输出
end Behavioral;
-- 定义全减器
entity full_suber is
Port ( a : in STD_LOGIC;
b : in STD_LOGIC;
sub_in : in STD_LOGIC;
diff : out STD_LOGIC;
s_out : out STD_LOGIC);
end full_suber;
architecture Behavioral of full_suber is
component h_suber -- 例化半减器
Port ( a : in STD_LOGIC;
b : in STD_LOGIC;
diff : out STD_LOGIC;
s_out : out STD_LOGIC);
end component;
signal temp_diff, temp_s_out : std_logic;
begin
h_suber_inst : h_suber port map(a, b, temp_diff, temp_s_out); -- 连接半减器
diff <= temp_diff xor sub_in; -- 异或运算实现差
s_out <= (not temp_diff) and sub_in; -- 与非运算实现借位输出
end Behavioral;
```
注意,这里先定义了半减器,然后在全减器中使用了例化语句将两个半减器连接起来,实现了全减器的功能。