scancnt4b.vhd

正弦信号发生器（可扫频）通过验证 正弦信号发生器

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

ENTITY SCANCNT4B IS
    PORT(  CLK: IN  STD_LOGIC;
           EN: IN STD_LOGIC;
           FOUT: OUT STD_LOGIC_VECTOR(3 DOWNTO 0)
        );
END;

ARCHITECTURE behav OF SCANCNT4B IS

   BEGIN
    PROCESS(CLK,EN)      
        VARIABLE CNT4: STD_LOGIC_VECTOR(3 DOWNTO 0);
      BEGIN
        IF CLK'EVENT AND CLK='1' THEN IF EN='1' THEN
           IF CNT4<"1111" THEN CNT4:=CNT4+1;
            ELSE CNT4 :="0000";
           END IF;
          END IF;
        END IF;
        FOUT<=CNT4;
    END PROCESS;
END;