原创 【转】8位总线收发器74245 vhdl源程序

--8位总线收发器：74245 vhdl

-- Octal Bus Transceiver
-- This example shows the use of the high impedance literal 'Z' provided by std_logic.
-- The aggregate '(others => 'Z')' means all of the bits of B must be forced to 'Z'.
-- Ports A and B must be resolved for this model to work correctly (hence std_logic rather than std_ulogic).

library IEEE;
use IEEE.Std_logic_1164.all;

entity HCT245 is
port(A, B : inout std_logic_vector(7 downto 0);
DIR, GBAR : in std_logic);
end HCT245;

architecture VER1 of HCT245 is
begin
A <= B when (GBAR = '0') and (DIR = '0') else (others => 'Z');
B <= A when (GBAR = '0') and (DIR = '1') else (others => 'Z');
end VER1;