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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_08_fg_08_06.vhd,v 1.1.1.1 2001-08-22 18:20:48 paw Exp $
-- $Revision: 1.1.1.1 $
--
-- ---------------------------------------------------------------------
package cpu_types is
constant word_size : positive := 16;
constant address_size : positive := 24;
subtype word is bit_vector(word_size - 1 downto 0);
subtype address is bit_vector(address_size - 1 downto 0);
type status_value is ( halted, idle, fetch, mem_read, mem_write,
io_read, io_write, int_ack );
subtype opcode is bit_vector(5 downto 0);
function extract_opcode ( instr_word : word ) return opcode;
constant op_nop : opcode := "000000";
constant op_breq : opcode := "000001";
constant op_brne : opcode := "000010";
constant op_add : opcode := "000011";
-- . . .
end package cpu_types;
-- not in book
package body cpu_types is
function extract_opcode ( instr_word : word ) return opcode is
begin
return work.cpu_types.op_nop;
end function extract_opcode;
end package body cpu_types;
-- end not in book
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