设计要求：
竞赛计时分两个阶段：每方50秒的规定用时和每方每步8秒的读秒。
1．可分别显示甲乙双方规定用时阶段的已用时间和读秒阶段(8秒)的倒计时；
2．设置两路输入模拟双方落子，在规定用时阶段，一路信号有效时会暂停本方计时并继续对方计时，而在读秒倒计时阶段，它用来暂停本方倒计时，并启动对方8秒倒计时；
3. 若其中一方倒计时到零，则用一路输出表示该方超时负，比赛结束
VHDL：
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY cnt50s IS
PORT (
clk : IN STD_LOGIC;
cir : IN STD_LOGIC;
en : IN STD_LOGIC;
co : OUT STD_LOGIC;
sunit : OUT STD_LOGIC_VECTOR (3 DOWNTO 0);
stent : OUT STD_LOGIC_VECTOR (3 DOWNTO 0)
);
END cnt50s;
ARCHITECTURE a OF cnt50s IS
SIGNAL unit : STD_LOGIC_VECTOR (3 DOWNTO 0);
SIGNAL tent : STD_LOGIC_VECTOR (3 DOWNTO 0);
BEGIN
PROCESS (clk, cir, en)
BEGIN
IF (cir = '1') THEN
co <= '0';
unit <= "1001";
tent <= "0100";
ELSIF (clk'EVENT AND clk = '1' AND en = '1') THEN
unit <= unit - 1;
IF (unit = "0000") THEN
unit <= "1001";
tent <= tent - 1;
IF (tent = "0000") THEN
co <= '1';
END IF;
END IF;
END IF;
END PROCESS;
sunit <= unit;
stent <= tent;
END a;
Testbench：
LIBRARY ieee;
USE ieee.std_logic_1164.all;
ENTITY cnt50s_vhd_tst IS
END cnt50s_vhd_tst;
ARCHITECTURE cnt50s_arch OF cnt50s_vhd_tst IS
-- constants
-- signals
SIGNAL cir : STD_LOGIC;
SIGNAL clk : STD_LOGIC;
SIGNAL co : STD_LOGIC;
SIGNAL en : STD_LOGIC;
SIGNAL stent : STD_LOGIC_VECTOR(3 DOWNTO 0);
SIGNAL sunit : STD_LOGIC_VECTOR(3 DOWNTO 0);
COMPONENT cnt50s
PORT (
cir : IN STD_LOGIC;
clk : IN STD_LOGIC;
co : OUT STD_LOGIC;
en : IN STD_LOGIC;
stent : OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
sunit : OUT STD_LOGIC_VECTOR(3 DOWNTO 0)
);
END COMPONENT;
BEGIN
i1 : cnt50s
PORT MAP (
-- list connections between master ports and signals
cir => cir,
clk => clk,
co => co,
en => en,
stent => stent,
sunit => sunit
);
init : PROCESS
-- variable declarations
BEGIN
cir<='1';wait for 30ns;
cir<='0';
en<='1';wait for 40ns; -- code that executes only once
WAIT;
END PROCESS init;
always : PROCESS
BEGIN
clk<='0';wait for 10ns;
clk<='1';wait for 10ns;
END PROCESS always;
END cnt50s_arch;
VHDL：
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY cnt8s IS
PORT (
clk : IN STD_LOGIC;
cir : IN STD_LOGIC;
en : IN STD_LOGIC;
co : OUT STD_LOGIC;
sunit : OUT STD_LOGIC_VECTOR (3 DOWNTO 0));
END cnt8s;
ARCHITECTURE a OF cnt8s IS
SIGNAL unit : STD_LOGIC_VECTOR (3 DOWNTO 0);
BEGIN
PROCESS (clk, cir, en)
BEGIN
IF (cir = '1') THEN
co <= '0';
unit <= "0111";
ELSIF (clk'EVENT AND clk = '1' AND en = '1') THEN
unit <= unit - 1;
IF (unit = "0000") THEN
co <= '1';
END IF;
END IF;
END PROCESS;
sunit <= unit;
END a;
Testbench：
LIBRARY ieee;
USE ieee.std_logic_1164.all;
ENTITY cnt8s_vhd_tst IS
END cnt8s_vhd_tst;
ARCHITECTURE cnt8s_arch OF cnt8s_vhd_tst IS
-- constants
-- signals
SIGNAL cir : STD_LOGIC;
SIGNAL clk : STD_LOGIC;
SIGNAL co : STD_LOGIC;
SIGNAL en : STD_LOGIC;
SIGNAL sunit : STD_LOGIC_VECTOR(3 DOWNTO 0);
COMPONENT cnt8s
PORT (
cir : IN STD_LOGIC;
clk : IN STD_LOGIC;
co : OUT STD_LOGIC;
en : IN STD_LOGIC;
sunit : OUT STD_LOGIC_VECTOR(3 DOWNTO 0)
);
END COMPONENT;
BEGIN
i1 : cnt8s
PORT MAP (
-- list connections between master ports and signals
cir => cir,
clk => clk,
co => co,
en => en,
sunit => sunit
);
init : PROCESS
-- variable declarations
BEGIN
cir<='1';wait for 30ns;
cir<='0';
en<='1';wait for 40ns; -- code that executes only once
WAIT;
END PROCESS init;
always : PROCESS
-- optional sensitivity list
-- ( )
-- variable declarations
BEGIN
clk<='0';wait for 10ns;
clk<='1';wait for 10ns;
END PROCESS always;
END cnt8s_arch;
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY controler IS
PORT (
count50a, count8a, count50b, count8b : IN STD_LOGIC;
cr, s : IN STD_LOGIC;
en50a, en8a, en50b, en8b, cr8a, cr8b : OUT STD_LOGIC
);
END controler;
ARCHITECTURE a OF controler IS
BEGIN
PROCESS (s, count50a)
BEGIN
IF (s = '0') THEN --s=0乙计时
en50a <= '0';
ELSIF (count50a = '0') THEN
en50a <= '1';
ELSE
en50a <= '0';
END IF;
END PROCESS;
-- process s, count50a, count8a.
PROCESS (s, count50a, count8a)
BEGIN
IF (count8a = '1') THEN
en8a <= '0'; -----------
ELSIF (count50a = '1' AND s ='1') THEN
en8a <= '1';
ELSE
en8a <= '0';
END IF;
END PROCESS;
-- process s, count50b.
PROCESS (s, count50b)
BEGIN
IF (s = '1') THEN --s=1 甲计时
en50b <= '0';
ELSIF (count50b = '0') THEN
en50b <= '1';
ELSE
en50b <= '0';
END IF;
END PROCESS;
-- process s, count50b, count8b
PROCESS (s, count50b, count8b)
BEGIN
IF (count8b = '1') THEN
en8b <= '0';
ELSIF (count50b = '1' AND s = '0') THEN
en8b <= '1';
ELSE
en8b <= '0';
END IF;
END PROCESS;
-- process s and cr.
PROCESS (s, cr)
BEGIN
IF (cr = '1') THEN
cr8a <= '1';
ELSIF (s = '0') THEN
cr8a <= '1';
ELSE
cr8a <= '0';
END IF;
END PROCESS;
-- process s and cr.
PROCESS (s,cr)
BEGIN
IF (cr = '1') THEN
cr8b <= '1';
ELSIF (s = '1') THEN
cr8b <= '1';
ELSE
cr8b <= '0';
END IF;
END PROCESS;
END a;