cnt24.vhd

来自「1．6个数码管动态扫描显示驱动 2．按键模式选择(时分秒)与调整控制 3．用」· VHDL 代码 · 共 36 行

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;

ENTITY cnt24 IS
PORT(en,clk: IN STD_LOGIC;
      qh,ql:OUT STD_LOGIC_VECTOR(3 DOWNTO 0));
END cnt24;

ARCHITECTURE arc OF cnt24 IS
SIGNAL ah,al:STD_LOGIC_VECTOR(3 DOWNTO 0);
BEGIN
qh<=ah;
ql<=al;
  PROCESS(en,clk)
  BEGIN
    IF(clk'EVENT AND clk='1')THEN
      IF(en='1')THEN
        IF(ah="0000" AND al="1001")THEN
          ah<="0001";
          al<="0000";
        ELSIF(ah="0001" AND al="1001")THEN
          ah<="0010";
          al<="0000";
        ELSIF(ah="0010" AND al="0011")THEN
          ah<="0000";
          al<="0000";
        ELSE
          al<=al+'1';
        END IF;
      END IF;
     END IF;
   END PROCESS;
END arc;