scan.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 45 行

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

ENTITY scan IS
PORT(clk:IN STD_LOGIC;
     d:OUT STD_LOGIC_VECTOR(2 DOWNTO 0));
END scan;

ARCHITECTURE arc OF scan IS
TYPE mystate IS (s0,s1,s2,s3,s4,s5);
SIGNAL c_state,n_state: mystate;
BEGIN
  PROCESS(c_state)
  BEGIN
    CASE c_state IS
    WHEN s0=>
         n_state<=s1;
         d<="000";
    WHEN s1=>
       	 n_state<=s2;
       	 d<="001";
    WHEN s2=>
     	 n_state<=s3;
     	 d<="100";
    WHEN s3=>
    	 n_state<=s4;
    	 d<="101";
    WHEN s4=>
      	 n_state<=s5;
      	 d<="110";
    WHEN s5=>
     	 n_state<=s0;
     	 d<="111";
    END CASE;
  END PROCESS;
  
  PROCESS(clk)
  BEGIN
    IF(clk'EVENT AND clk='1')THEN
      c_state<=n_state;
    END IF;
  END PROCESS;
END arc;