VHDL课考前预习（2）——代码篇
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VHDL笔记,本科学习,电子垃圾

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本文最后更新于 1102 天前，其中的信息可能已经有所发展或是发生改变。

概述

概述部分主要是期中考会考

目前美国的设计公司用的主要是Verilog HDL，欧洲的设计公司主要用VHDL
Verilog HDL 的语法非常宽松，在大型电路设计的时候容易出现问题，但对于初学者来说相对容易上手
VHDL 的语法非常严谨，不太好上手
从 2002 年开始，出现了两种语言联合编译

3-8 译码器

这是 3-8 译码器的真值表

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY decoder3to8 IS
PORT(A:IN STD_LOGIC_VECTOR(2 DOWNtO 0);
    ST,STA,STB:IN STD_LOGIC;
    Y:OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
END ENTITY decoder3to8;

ARCHITECTURE 3to8 OF decoder3to8
BEGIN
PROCESS(A)
BEGIN
IF ST="1" AND STA="0" AND STB="0" THEN
BEGIN
CASE(A) IS
    WHEN "000" => Y <= "11111110";
    WHEN "001" => Y <= "11111101";
    WHEN "010" => Y <= "11111011";
    WHEN "011" => Y <= "11110111";
    WHEN "100" => Y <= "11101111";
    WHEN "101" => Y <= "11011111";
    WHEN "110" => Y <= "10111111";
    WHEN OTHERS => Y <= "01111111";
END CASE;
ELSE Y <= "11111111";
END IF;
END PROCESS;
END 3to8;

4 选 1 选择器

试分别用IF_THEN语句、WHEN_ELSE 和CASE语句的表达方式写出4选1多路选择器的VHDL程序，选通控制端有4个输入:S0、S1、S2、S3。当且仅当S0=0,时:Y=A;S1=0时:Y=B;S2=0时:Y=C; S3=0时:Y=D。

LIBRERY  IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY  mux41  IS
    PORT( S0,S1,S2,S3 :IN  STD_LOGIC;
               A,B,C,D : IN  STD_LOGIC;
                     Y: OUT: STD_LOGIC );
END ENTITY mux41;
ARCHITECTURE  one  OF  mux41  IS
SIGNAL  S : STD_LOGIC_VECTOR(3 DOWNTO 0);
    BEGIN
         S=S3&S2&S1&S0 ;
      PROCESS(S0,S1,S2,S3)    BEGIN
               IF  (S= "1110") THEN  Y<=A   ;
          ELSIF (S= "1101" ) THEN  Y<=B;
           ELSIF (S= "1011" ) THEN  Y<=C;
            ELSIF (S= "0111" ) THEN  Y<=D ;
      END IF ;
    END PROCESS;
END  one；

试用WITH- -SELECT语句写出4选1多路选择器的VHDL程序，选通控制端有4个输入:S0、S1、S2、S3。当且仅当S0=0,时:Y=A;S1=0时:Y=B;S2=0时:Y=C; S3=0时:Y=D。

LIBRERY  IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY  mux41  IS
    PORT( S0,S1,S2,S3 :IN  STD_LOGIC;
               A,B,C,D : IN  STD_LOGIC;
                     Y: OUT: STD_LOGIC );
END ENTITY mux41;
ARCHITECTURE  one  OF  mux41  IS
SIGNAL  S : STD_LOGIC_VECTOR(3 DOWNTO 0);
    BEGIN
         S=S3&S2&S1&S0 ;
    WITH  S  SELECT
         Y<=A  WHEN "1110" ;
                B  WHEN "1101" ;
                C  WHEN "1011" ;
                D  WHEN "0111" ;
                NULL  WHEN  OTHERS;
END  one；

试用IWHEN_ELSE 语句写出4选1多路选择器的VHDL程序，选通控制端有4个输入:S0、S1、S2、S3。当且仅当S0=0,时:Y=A;S1=0时:Y=B;S2=0时:Y=C; S3=0时:Y=D。

LIBRERY  IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

ENTITY  mux41  IS

    PORT( S0,S1,S2,S3 :IN  STD_LOGIC;

               A,B,C,D : IN  STD_LOGIC;

                     Y: OUT: STD_LOGIC );

END ENTITY mux41;

ARCHITECTURE  one  OF  mux41  IS

SIGNAL  S : STD_LOGIC_VECTOR(3 DOWNTO 0);

    BEGIN

         S=S3&S2&S1&S0 ;

           Y<=A  WHEN  S="1110"  ELSE ;

                  B  WHEN S="1101"  ELSE ;

                  C  WHEN S="1011" ELSE;

                  D  WHEN S= "0111" ELSE;

                  NULL  ;

END  one；

试用CASE语句写出4选1多路选择器的VHDL程序，选通控制端有4个输入:S0、S1、S2、S3。当且仅当S0=0,时:Y=A;S1=0时:Y=B;S2=0时:Y=C; S3=0时:Y=D。

LIBRERY  IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

ENTITY  mux41  IS

    PORT( S0,S1,S2,S3 :IN  STD_LOGIC;

               A,B,C,D : IN  STD_LOGIC;

                     Y: OUT: STD_LOGIC );

END ENTITY mux41;

ARCHITECTURE  one  OF  mux41  IS

SIGNAL  S : STD_LOGIC_VECTOR(3 DOWNTO 0);

    BEGIN

         S=S3&S2&S1&S0 ;

      PROCESS(S0,S1,S2,S3)    BEGIN

          CASE (S)  IS

                  WHEN "1110"  => Y<=A   ;

                   WHEN "1101"  => Y<=B;

                   WHEN "1011"  => Y<=C;

                   WHEN "0111"  => Y<=D ;

                  WHEN  OTHERS =>NULL  ;

      END  CASE;

    END PROCESS;

END  one；

设计一个求补码的VHDL程序

输入数据是一个有符号的8位二进制数

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY buma IS
PORT(a:IN STD_LOGIC_VECTOR(7 DOWNTO 0);
    y:OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
END buma;
ARCHITECTURE arc OF buma IS
SIGNAL tmp:STD_LOGIC_VECTOR(7 DOWNTO 0);
BEGIN
PROCESS(a)
BEGIN
    IF a(7)='0' THEN
   y<=a;
    ELSE
   tmp(7)<='1';
    FOR i IN 0 TO 6 LOOP
   tmp(i)<=NOT a(i);
   y<=tmp+1;
    END LOOP;
   END IF;
  END PROCESS;
END arc;

设计一个4 位乘法器

为此首先设计一个加法器，用例化语句调用这个加法器，用移位相加的方式完成乘法
并以此项设计为基础,使用GENERIC参数传递的功能设计一个16位乘法器

USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
USE IEEE.STD_LOGIC_ARITH.ALL;
ENTITY MULT4B IS
GENERIC( S: INTEGER:=4); --定义参数S为整数类型，且等于4 
PORT( R: OUT STD_LOGIC_VECTOR(2*S-1 DOWNTO 0);
A,B: IN STD_LOGIC_VECTOR(S-1 DOWNTO 0)); 
END ENTITY MULT4B;
ARCHITECTURE ONE OF MULT4B IS COMPONENT addern IS
PORT(a,b: IN STD_LOGIC_VECTOR; result: out STD_LOGIC_VECTOR);
END COMPONENT;
SIGNAL A0: STD_LOGIC_VECTOR(2*S-1 DOWNTO 0);
SIGNAL RR3,RR2,RR1,RR0,ZZ1,ZZ0: STD_LOGIC_VECTOR(2*S-1 DOWNTO 0);
BEGIN
A0<=CONV_STD_LOGIC_VECTOR(0,S) & A;
PROCESS(A,B) 
BEGIN
IF(B(0)='1')THEN RR0<=TO_STDLOGICVECTOR(TO_BITVECTOR(A0) SLL 0);
ELSE RR0<=(OTHERS=>'0');
END IF;
IF(B(1)='1')THEN RR1<=TO_STDLOGICVECTOR(TO_BITVECTOR(A0) SLL 1);
ELSE RR1<=(OTHERS=>'0');
END IF;
IF(B(2)='1')THEN RR2<=TO_STDLOGICVECTOR(TO_BITVECTOR(A0) SLL 2);
ELSE RR2<=(OTHERS=>'0');
END IF;
IF(B(3)='1')THEN RR3<=TO_STDLOGICVECTOR(TO_BITVECTOR(A0) SLL 3);
ELSE RR3<=(OTHERS=>'0');
END IF;
END PROCESS;
u0: addern PORT MAP(a=>RR0,b=>RR1,result=>ZZ0);
u1: addern PORT MAP(a=>ZZ0,b=>RR2,result=>ZZ1);
u2: addern PORT MAP(a=>ZZ1,b=>RR3,result=>R);
END ARCHITECTURE ONE;

D类触发器

写出具有上升沿触发的D触发器的VHDL语言代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY DFF1 IS
    PORT(CLK,D:IN STD_LOGIC;
        Q:OUT STD_LOGIC);
END;
ARCHITECTURE bhv OF DFF1 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 bhv;

写出具有异步复位和时钟使能的上升沿触发的D触发器的VHDL语言代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY DFF2 IS
PORT(CLK,RST,EN,D:IN STD_LOGIC;
    Q:OUT SYD_LOGIC);
END;
ARCHITECTURE bhv OF DFF2 IS
    SIGNAL Q1:STD_LOGIC;
BEGIN
    PROCESS(CLK,Q1,RST,EN) 
    BEGIN
IF RST='1' THEN Q<='0';
ELSIF CLK'EVENT AND CLK='1'THEN 
IF EN='1' THEN Q1<=D;
END IF;
END PROCESS;
Q<=Q1;
END bhv;

写出具有同步复位控制的上升沿触发的D触发器的VHDL语言代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY DFF3 IS
PORT(CLK,RST,D:IN ATD_LOGIC;
    Q:OUT STD_LOGIC);
END;
ARCHITECTURE bhv OF DFF3 IS
SIGNAL Q1:STD_LOGIC;
BEGIN
PROCESS (CLK,Q1,RST)
BEGIN
IF CLK'EVENT AND CLK='1' THEN
    IF RST='1' THEN Q1<='0';
ELSE Q1<=D;
END IF;
END IF;
END PROCESS;
Q<=Q1;
END bhv;

锁存器

写出基本锁存器的VHDL语言代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENITIY LTCH2 IS
PORT (CLK,D:IN STD_LOGIC;
     Q:OUT STD_LOGIC);
END;
ARCHITECTURE bhv OF LTCH2 IS
BEGIN
PROCESS (CLK,D)
    BEGIN
    IF CLK='1' THEN Q<=D;
END IF;
END PROCESS;
END bhv;

写出含清零控制的锁存器的VHDL语言代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY LTCH3 IS
PORT (CLK,D:IN STD_LOGIC;
     Q:OUT STD_LOGIC);
END;
ARCHITECTURE bhv OF LTCH3 IS
BEGIN
PROCESS (CLK,D,RST)
    BEGIN
    IF RST='1' THEN Q<='0';
ELSIF CLK='1' THEN Q<=D;
END IF;
END PROCESS;
END bhv;

加法器

写出4位二进制加法计数器的VHDL语言代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY CNT4 IS
    PORT (CLK: IN BIT;
         Q:BUFFER INTEGER RANGE 15 DOWNTO 0);
END CNT4;
ARCHITECTURE BHV OF CNT4 IS
    BEGIN
        PROCESS (CLK)
        BEGIN 
            IF CLK'ENENT AND CLK='1' THEN Q<=Q+1;
            END IF;
        END PROCESS;
END BHV;

移位寄存器

写出带有同步预置控制的8位 右移 移位寄存器的VHDL代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY SHFT IS
    PORT (CLK,LOAD: IN STD_LOGIC;
         QB:OUT STD_LOGIC;
         DIN : IN STD_LOGIC_VECTOR(7 DOWNTO 0);
         DOUT : OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
END SHFT;
ARCHITECTURE BEHAV OF SHFT IS
    SIGNAL REG8 :STD_LOGIC_VECTOR(7 DOWNTO 0)
    BEGIN
        PROCESS (CLK,LOAD)
        BEGIN
            IF CLK'ENENT AND CLK='1' THEN
                IF LOAD ='1' THEN 
                    REG8 <= DIN;
                ELSE REG8(6 DOWNTO 0) <= REG(7 DOWNTO 1);
                END IF;
            END IF;
        END PROCESS;
        QB <=REG8(0);
        DOUT<=REG8;
END BEHAV;

三态控制门电路

写出8位三态控制门电路的VHDL描述语言代码

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY tri_s IS
port (enable : IN STD_LOGIC;
datain : IN STD_LOGIC_VECTOR(7 DOWNTO 0);
dataout : OUT STD_LOGIC_VECTOR(7 DOWNTO 0));
END tri_s ,;
ARCHITECTURE bhv OF tri_s IS
BEGIN
PROCESS(enable,datain) BEGIN
IF enable=,11 THEN dataout <= datain ;
ELSE dataout <="ZZZZZZZZ" ; END IF ;
END PROCESS;
END bhv;
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