EDA技术全减器的VHDL描述

Question

1.设计半减器，用例化语句将他们连接起来，图以上传。
2.设计全减器，以全减器为基本硬件，构成串行借位的8位减法器，用例化语句来完成设计

Answer 1

以下内容部分参考ChatGPT模型：

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半减器的VHDL描述：

library ieee;
use ieee.std_logic_1164.all;

entity half_subtractor is
    port (
        A : in std_logic;
        B : in std_logic;
        Diff : out std_logic;
        Borrow : out std_logic
    );
end half_subtractor;

architecture behavior of half_subtractor is
begin
    Diff <= A xor B;
    Borrow <= not A and B;
end behavior;

全减器的VHDL描述：

library ieee;
use ieee.std_logic_1164.all;

entity full_subtractor is
    port (
        A : in std_logic;
        B : in std_logic;
        Bin : in std_logic;
        Diff : out std_logic;
        Bout : out std_logic
    );
end full_subtractor;

architecture behavior of full_subtractor is
begin
    process (A, B, Bin)
    begin
        Diff <= A xor B xor Bin;
        Bout <= (not A and B and Bin) or (A and not B and Bin) or (A and B and not Bin) or (not A and not B and Bin);
    end process;
end behavior;

串行借位的8位减法器的VHDL描述：

library ieee;
use ieee.std_logic_1164.all;

entity subtractor is
    port (
        A : in std_logic_vector(7 downto 0);
        B : in std_logic_vector(7 downto 0);
        Cin : in std_logic;
        Difference : out std_logic_vector(7 downto 0);
        Cout : out std_logic
    );
end subtractor;

architecture behavior of subtractor is
    component full_subtractor is
        port (
            A : in std_logic;
            B : in std_logic;
            Bin : in std_logic;
            Diff : out std_logic;
            Bout : out std_logic
        );
    end component;
    
    signal D : std_logic_vector(7 downto 0);
    signal Bc : std_logic_vector(7 downto 0);
begin
    D(0) <= A(0) xor B(0) xor Cin;
    Bc(0) <= (not A(0) and B(0) and Cin) or (A(0) and not B(0) and Cin) or (A(0) and B(0) and not Cin) or (not A(0) and not B(0) and Cin);
    
    subtractor_loop : for i in 1 to 7 generate
        Fs : full_subtractor port map (A(i), B(i), Bc(i-1), D(i), Bc(i));
    end generate;
    
    Difference <= D;
    Cout <= Bc(7);
end behavior;

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