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-- Copyright (C) 1996 Morgan Kaufmann Publishers, Inc
-- This file is part of VESTs (Vhdl tESTs).
-- VESTs is free software; you can redistribute it and/or modify it
-- under the terms of the GNU General Public License as published by the
-- Free Software Foundation; either version 2 of the License, or (at
-- your option) any later version.
-- VESTs is distributed in the hope that it will be useful, but WITHOUT
-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-- FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
-- for more details.
-- You should have received a copy of the GNU General Public License
-- along with VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-- ---------------------------------------------------------------------
--
-- $Id: ch_05_fg_05_09.vhd,v 1.2 2001-10-26 16:29:34 paw Exp $
-- $Revision: 1.2 $
--
-- ---------------------------------------------------------------------
-- not in book
entity computer_system is
end entity computer_system;
-- end not in book
architecture abstract of computer_system is
subtype word is bit_vector(31 downto 0);
signal address : natural;
signal read_data, write_data : word;
signal mem_read, mem_write : bit := '0';
signal mem_ready : bit := '0';
begin
cpu : process is
variable instr_reg : word;
variable PC : natural;
-- . . . -- other declarations
begin
loop
address <= PC;
mem_read <= '1';
wait until mem_ready = '1';
instr_reg := read_data;
mem_read <= '0';
wait until mem_ready = '0';
PC := PC + 4;
-- . . . -- execute the instruction
end loop;
end process cpu;
memory : process is
type memory_array is array (0 to 2**14 - 1) of word;
variable store : memory_array := (
-- . . .
-- not in book
0 => X"0000_0000",
1 => X"0000_0004",
2 => X"0000_0008",
3 => X"0000_000C",
4 => X"0000_0010",
5 => X"0000_0014",
others => X"0000_0000"
-- end not in book
);
begin
wait until mem_read = '1' or mem_write = '1';
if mem_read = '1' then
read_data <= store( address / 4 );
mem_ready <= '1';
wait until mem_read = '0';
mem_ready <= '0';
else
-- . . . -- perform write access
end if;
end process memory;
end architecture abstract;
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