clk_choose.vhd.bak

数字显示当前的小时、分钟、秒； 2、可以预置为12小时计时显示和24小时计时显示； 3、一个调节键

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY CLK_CHOOSE IS
PORT(CLK_MC,CLK_1HZ,SEC_COUT,MIN_COUT:IN STD_LOGIC;
       SET_TIME:IN STD_LOGIC_VECTOR(1 DOWNTO 0);
       HOUR_CLK,MIN_CLK,SEC_CLK:OUT STD_LOGIC);
END ENTITY;
ARCHITECTURE BEHAV OF CLK_CHOOSE IS
BEGIN     
   PROCESS (SET_TIME,CLK_MC,CLK_1HZ)
     BEGIN
      CASE SET_TIME IS
        WHEN "01" =>
          SEC_CLK<=CLK_MC;
          MIN_CLK<='0';
          HOUR_CLK<='0';
         WHEN "10" =>
          SEC_CLK<='0';
          MIN_CLK<=CLK_MC;
          HOUR_CLK<='0';
          WHEN "11" =>
          SEC_CLK<='0';
          MIN_CLK<='0';
          HOUR_CLK<=CLK_MC;
           WHEN OTHERS =>
          SEC_CLK<=CLK_1HZ;
          MIN_CLK<=SEC_COUT;
          HOUR_CLK<=MIN_COUT;
         END CASE;
       END PROCESS;
     END BEHAV;