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-- Copyright (C) 1996 Morgan Kaufmann Publishers, Inc
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-- This file is part of VESTs (Vhdl tESTs).
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-- VESTs is free software; you can redistribute it and/or modify it
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-- under the terms of the GNU General Public License as published by the
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-- Free Software Foundation; either version 2 of the License, or (at
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-- your option) any later version. 
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-- VESTs is distributed in the hope that it will be useful, but WITHOUT
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-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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-- FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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-- for more details. 
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-- You should have received a copy of the GNU General Public License
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-- along with VESTs; if not, write to the Free Software Foundation,
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-- Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
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-- ---------------------------------------------------------------------
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--
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-- $Id: ch_08_fg_08_06.vhd,v 1.1.1.1 2001-08-22 18:20:48 paw Exp $
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-- $Revision: 1.1.1.1 $
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--
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-- ---------------------------------------------------------------------
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package cpu_types is
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  constant word_size : positive := 16;
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  constant address_size : positive := 24;
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  subtype word is bit_vector(word_size - 1 downto 0);
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  subtype address is bit_vector(address_size - 1 downto 0);
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  type status_value is ( halted, idle, fetch, mem_read, mem_write,
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                         io_read, io_write, int_ack );
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  subtype opcode is bit_vector(5 downto 0);
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  function extract_opcode ( instr_word : word ) return opcode;
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  constant op_nop : opcode := "000000";
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  constant op_breq : opcode := "000001";
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  constant op_brne : opcode := "000010";
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  constant op_add : opcode := "000011";
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  -- . . .
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end package cpu_types;
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-- not in book
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package body cpu_types is
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  function extract_opcode ( instr_word : word ) return opcode is
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  begin
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    return work.cpu_types.op_nop;
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  end function extract_opcode;
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end package body cpu_types;
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-- end not in book
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