FPGA-VHDL实现10进制减法计数器——基于ISE14.7平台_ise中十进制计数器

 本文使用VHDL语言设计10进制减法计数器，附带清零和置数功能。将项目分为分频器、计数器、数码管三个部分，采用元器件例化的方式，自顶向下设计。

一、代码

1.1 顶层文件

 顶层文件将三个模块元器件例化和元器件映射。

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;
entity CNT10 is
    port(
          CLK,RST,EN: in std_logic;
		  data_hex : out std_logic_vector(7 downto 0);
          DOUT : out std_logic_vector (3 downto 0);
          COUT : OUT std_logic;
		  DINT : in std_logic_vector(3 downto 0);
		  DCON : in std_logic;
		  Dtest : out std_logic;
		  DtestMORE : out std_logic_vector(3 downto 0)
    );
end CNT10;
architecture behav of CNT10 is
	
	component digital is		
	port(
		data : IN std_logic_vector(3 downto 0);
		show : OUT std_logic_vector(7 downto 0);
		com : OUT std_logic_vector(3 downto 0)
	);
	end component digital;
	
	component Counter1 is
	port(
		clk : IN std_logic;
		en : IN std_logic;
		out1 : out std_logic
	);
	end component Counter1;
	
	component count10 is
	port(
		signal clk,rst,en : in std_logic;
		signal DCON : in std_logic;
		signal DINT : in std_logic_vector(3 downto 0);
		signal q : inout std_logic_vector(3 downto 0)
	);
	end component count10;


signal clk1 : std_logic;
signal data_sum : std_logic_vector(7 downto 0);
signal data_get : std_logic_vector(3 downto 0);
signal cq10 : std_logic_vector(3 downto 0) := (others => '0');

begin
 
part1:
	 Counter1 port map
	 (
		clk => CLK,
		en => EN,
		out1 => clk1
	 );
	 
part2:
	count10 port map
	(
		clk => clk1,
		rst => RST,
		en => EN,
		DCON => DCON,
		DINT => DINT,
		q => cq10
	);
	
part3:	 
	 digital port map
	 (
		data => data_get,
		show => data_sum,
		com => DOUT
	 );
	 
	 Dtest <= clk1;
	 DtestMORE <= cq10;
	 data_hex <= data_sum;
	 data_get <= cq10;
	 
end behav;
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1.2 分频器

 分频器用于将clk时钟信号放大相应倍数，否则由于时钟频率太高，计数值的减少效果看不出。out1为分频后的clk信号。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_logic_unsigned.all;
entity Counter1 is
port
(
	clk : in std_logic;
	en : in std_logic;
	out1 : out std_logic
);
end Counter1;

architecture Behavioral of Counter1 is
signal cp : std_logic_vector(25 downto 0) :=(others => '0');	
signal clk1 : std_logic := '0';
begin
	process(clk)
		begin
		if clk 'event and clk = '1' then
				if en = '1' then
					if cp = "10111110101111000010000000" then
						cp <= "00000000000000000000000000";
						clk1 <= not clk1;
					else
						cp <= cp + 1;
					end if;
					out1 <= clk1;
				end if;
			end if;
	end process;
end Behavioral;
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1.3 计数器

 计数器实现从9倒数到0，每秒倒数一次。rst为清零端，DCON为置数端，置数的数据为DINT。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use ieee.std_Logic_unsigned.all;


entity count10 is
port(
	signal clk,rst,en : in std_logic;
	signal DCON : in std_logic;
	signal DINT : in std_logic_vector(3 downto 0);
	signal q : out std_logic_vector(3 downto 0)
);
end count10;

architecture Behavioral of count10 is
	signal cq10 : std_logic_vector(3 downto 0) := (others => '0');
begin
	process(clk,rst,en)
	begin
		if rst = '1' then -- 清零
			cq10 <= "0000";	
		elsif clk'event and clk = '1' then
            if en = '1' then
					if DCON = '1'   then	--置数
						cq10 <= DINT;
					elsif cq10 = "0000" then
						cq10 <= "1001";
					else 
						cq10 <= cq10 - '1';
					end if;
            end if;
		end if;
	end process;
	q <= cq10;
end Behavioral;
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1.4 数码管

 数码管将计数器输出的值转译为数码管的段码而输出。

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
entity digital is
port(
  data : IN std_logic_vector(3 downto 0);
  show : OUT std_logic_vector(7 downto 0);
  com : OUT std_logic_vector(3 downto 0)
);
end digital;
architecture Behavioral of digital is

begin
	com <="1110";	--- 选中四个数码管中的最低位
	
	process(data)
	begin
	  case data is
	     WHEN "0000" => show <= "11000000";
		 WHEN "0001" => show <= "11111001";
		 WHEN "0010" => show <= "10100100";
		 WHEN "0011" => show <= "10110000";
		 WHEN "0100" => show <= "10011001";
		 WHEN "0101" => show <= "10010010";
		 WHEN "0110" => show <= "10000010";
		 WHEN "0111" => show <= "11111000";
		 WHEN "1000" => show <= "10000000";
		 WHEN "1001" => show <= "10010000";
		 when others => show <= "11111111";
	  end case;
    end process;
end Behavioral;
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二、仿真

创建VHDL Test Bench文件，在代码中begin后加入使能EN<=‘1’;代码。（注意仿真时需要将分频器、计数器赋初值，否则仿真将无数据。当然下载到器件上时却不需要初值，因为板子的高低电平有初值，而仿真却需要人为设定。）
ps：仿真时请修改分频器cp的值，否则无法仿真出。

 从仿真波形可以看出从9开始计数到0并循环不断。仿真时分频器设置为2倍频，从dtest参数可以看出，dtest参数的值为分频器的输出（看前面1.1顶层文件）。而dtestmore和data_hex的值对应于数码管所对应的值。


最后，如果需要完整工程的可以去下载：FPGA-VHDL实现十进制减法计数器。