signext_8_32.vhd

来自「DLX CPU VHDL CODE UNIVERSITY」· VHDL 代码 · 共 36 行

--
-- $RCSfile: signext_8_32.vhd,v $
-- $Revision: 1.1 $
-- $Author: petera $
-- $Date: 90/05/17 16:10:58 $
--

use WORK.dp32_types.all;

entity signext_8_32 is
  generic (Tpd : Time := unit_delay);
  port (a : in bit_8;
      	b : out bus_bit_32 bus;
	en : in bit);
end signext_8_32;

architecture behaviour of signext_8_32 is

begin

  b_driver: process (en, a) 
  begin
    if en = '1' then
      b(7 downto 0) <= a after Tpd;
      if a(7) = '1' then
      	b(31 downto 8) <= X"FFFF_FF" after Tpd;
      else
      	b(31 downto 8) <= X"0000_00" after Tpd;
      end if;
    else
      b <= null after Tpd;
    end if;
  end process b_driver;

end behaviour;