cnt10.vhd

10进制计数器

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;
ENTITY CNT10 IS
   PORT(CLK,RST,EN:IN STD_LOGIC;
               CQ:OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
COUT:OUT STD_LOGIC);
END CNT10;
ARCHITECTURE behav OF CNT10 IS
BEGIN
   PROCESS(CLK,RST,EN)
    VARIABLE CQI:STD_LOGIC_VECTOR(3 DOWNTO 0);
   BEGIN
      IF RST='1' THEN CQI:=(OTHERS=>'0');
      ELSIF CLK'EVENT AND CLK='1' THEN
        IF EN='1' THEN 
           IF CQI<9 THEN CQI:=CQI+1;
              ELSE CQI:=(OTHERS=>'0');END IF;
        END IF;
      END IF;
       IF CQI=9 THEN COUT<='0';
         ELSE  COUT<='1';END IF;
         CQ<=CQI;
 END PROCESS;
END behav;