pwide.vhd

初学ＶＨＤＬ有用的

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

ENTITY pwide IS
    PORT (
		CLK : IN STD_LOGIC;
        A, B : IN STD_LOGIC_VECTOR(3 DOWNTO 0);
		PSOUT : OUT STD_LOGIC
	);
END pwide;

ARCHITECTURE mixed OF pwide IS
COMPONENT CNT8
    PORT (
        CLK, LD : IN STD_LOGIC;
        D : IN STD_LOGIC_VECTOR(3 DOWNTO 0);
        CAO : OUT STD_LOGIC
    );
END COMPONENT;

    SIGNAL CAO1, CAO2 : STD_LOGIC;
    SIGNAL LD1, LD2 : STD_LOGIC;
	SIGNAL PSINT : STD_LOGIC;
BEGIN
    U1 : CNT8
	PORT MAP(
	    CLK => CLK,
		LD => LD1,
		D => A,
        CAO => CAO1
	);

    U2 : CNT8
	PORT MAP(
	    CLK => CLK,
		LD => LD2,
		D => B,
        CAO => CAO2
	);


	PROCESS(CAO1, CAO2)
	BEGIN
        IF CAO2 = '1' THEN
		    PSINT <= '0';
		ELSIF CAO1'EVENT AND CAO1 = '1' THEN
		    PSINT <= '1';
	    END IF;
	END PROCESS;

	LD1 <= PSINT;
	LD2 <= NOT PSINT;

	PSOUT <= PSINT;
END mixed;