异步置数(低有效)的10进制计数器

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异步置数(低有效)的10进制计数器 LIBRARY IEEE;USE IEEE.STD_LOGIC_1164.ALL;USE IEEE.STD_LOGIC_UNSIGNED.ALL; ENTITY counter10 IS    PORT( clk: IN STD_LOGIC;             load: IN STD_LOGIC;               din: IN STD_LOGIC_VECTOR(3 DOWNTO 0);             qout: OUT STD_LOGIC_VECTOR(3 DOWNTO 0);                  c: OUT STD_LOGIC);END counter10; ARCHITECTURE art OF counter10 IS    SIGNAL temp: STD_LOGIC_VECTOR(3 DOWNTO 0);BEGIN     PROCESS(clk,load,din)     BEGIN         IF(load='0') THEN              temp<=din;         ELSIF(clk'EVENT AND clk='1') THEN              IF(temp="1001") THEN                    temp<="0000";              ELSE                    temp<=temp+1;              END IF;         END IF;    END PROCESS;    qout<=temp;    c<='1' WHEN temp="1001" ELSE         '0';END art;