fen2.vhd

用vhdl写的

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
ENTITY FEN2 IS
PORT(
  SW_B,CS:IN STD_LOGIC;
  IN1,IN2,IN3:IN STD_LOGIC_VECTOR(7 DOWNTO 0);
  EW:OUT STD_LOGIC_VECTOR(7 DOWNTO 0)
);
END FEN2;
ARCHITECTURE A OF FEN2 IS
SIGNAL OT:STD_LOGIC_VECTOR(7 DOWNTO 0);
BEGIN
PROCESS(SW_B,CS,IN1,IN2,IN3,OT)
BEGIN
IF (SW_B='0') THEN OT<=IN2;
ELSIF(SW_B='1' AND CS='0') THEN  OT<=IN3;
ELSE
    OT<=IN1;
END IF;
EW<=OT;
END PROCESS;
END A;