VHDL语言入门整理

1.2选1多路选择器
Library ieee;
Use ieee.std_logic_1164.all;
Entity L1 is
Port
(
a,b,s:in std_logic;
y:out std_logic
);
End L1;
Architecture one of L1 is
Begin
Process(a,b,s)begin
If(s='0')then
y<=a;
Else
y<=b;
End if;
End process;
End one;
仿真结果：


2.4选1多路选择器
library ieee;
use ieee.std_logic_1164.all;
entity L2 is
port
(
a,b,c,d,s0,s1 : in std_logic;
y : out std_logic
);
end L2;
architecture two of L2 is
signal s : std_logic_vector(1 downto 0);
begin
s <= s1 & s0;
process(s1,s0) begin
case(s) is
when "00"=>y<=a;
when "01"=>y<=b;
when "10"=>y<=c;
when "11"=>y<=d;
when others=>null;
end case;
end process;
end two;

仿真结果：

3.半加器


VHDL语言描述：
library ieee;
use ieee.std_logic_1164.all;
entity L3 is
port(
A,B:in std_logic;
so,co:out std_logic
);
end L3;
architecture three of L3 is
begin
so<=A xor B;
co<=A and B;
end three;
仿真结果：

4.8位加法器
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity L6 is
port(
A,B:in std_logic_vector(7 downto 0);
CIN:in std_logic;
COUT:out std_logic;
DOUT:out std_logic_vector(7 downto 0)
);
end L6;
architecture abc of L6 is
signal DATA:std_logic_vector(8 downto 0);
begin
DATA<=('0'&A)+('0'&B)+("00000000"&CIN);
COUT<=DATA(8);
DOUT<=DATA(7 downto 0);
end abc;
仿真结果：

5.D触发器的vhdl描述
library ieee;
use ieee.std_logic_1164.all;
entity L7 is
port
(
clk,D:in std_logic;
Q:out std_logic
);
end L7;
architecture abc of L7 is
signal Q1:std_logic;
begin
process(clk,Q1) begin
if clk'event and clk='1'
then Q1<=D;
end if;
end process;
Q<=Q1;
end abc;
仿真结果：

6.统计向量中1的个数
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity L7 is
port
(
DIN:in std_logic_vector(7 downto 0);
CNTH:out std_logic_vector(3 downto 0)
);
end L7;
architecture abc of L7 is
begin
process(DIN)
variable Q:std_logic_vector(3 downto 0);
begin
Q:="0000";
for n in 0 to 7 loop
if(DIN(n)='1') then
Q:=Q+1;
end if;
end loop;
CNTH<=Q;
end process;
end abc;

7.双向端口
library ieee;
use ieee.std_logic_1164.all;
entity L7 is
port
(
control :in std_logic;
in1:in std_logic_vector(7 downto 0);
q:inout std_logic_vector(7 downto 0);
x:out std_logic_vector(7 downto 0)
);
end L7;
architecture abc of L7 is
begin
process(control,q,in1)begin
if(control='0')then
x<=q;
else
q<=in1;
x<="11111111";
end if;
end process;
end abc;

仿真结果：