seltime.vhd

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;
USE IEEE.STD_LOGIC_ARITH.ALL;
ENTITY SELTIME IS
  PORT(
        CLK:IN STD_LOGIC;
        SEC1,SEC0,MIN1,MIN0,H1,H0:IN STD_LOGIC_VECTOR(3 DOWNTO 0);
        DAOUT:OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
        SEL:OUT STD_LOGIC_VECTOR(2 DOWNTO 0));
END SELTIME;
ARCHITECTURE FUN OF SELTIME IS
   SIGNAL COUNT:STD_LOGIC_VECTOR(2 DOWNTO 0);
BEGIN
   SEL<=COUNT;
   PROCESS(CLK)
          BEGIN
              IF(CLK'EVENT AND CLK='1') THEN
                 IF(COUNT>="101") THEN
                    COUNT<="000";
                  ELSE
                    COUNT<=COUNT+1;
                  END IF;
               END IF;
  CASE COUNT IS
  WHEN"000"=>DAOUT<= SEC0;
  WHEN"001"=>DAOUT<= SEC1;
  WHEN"010"=>DAOUT<= MIN0;
  WHEN"011"=>DAOUT<= MIN1;
  WHEN"100"=>DAOUT<=H0;
  WHEN OTHERS =>DAOUT<=H1;
  END CASE;
  END PROCESS;
END FUN;