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[/] [System09/] [trunk/] [rtl/] [VHDL/] [spp.vhd] - Blame information for rev 124

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1 99 davidgb
--===========================================================================--
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--                                                                           --
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--              Synthesizable Simple Parallel Port                           --
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--                                                                           --
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--===========================================================================--
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--
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--  File name      : spp.vhd
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--
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--  Entity name    : spp
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--
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--  Purpose        : implements a Simple Parallel Port for System09
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--
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--  Dependencies   : ieee.Std_Logic_1164
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--                   ieee.std_logic_unsigned
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--
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--  Uses           : None
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--
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--  Author         : John E. Kent      
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--
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--  Email          : dilbert57@opencores.org      
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--
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--  Web            : http://opencores.org/project,system09
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--
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--  Description    : Register Memory Map
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--
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--  Address                                MSB                         LSB
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--                                    Bit:   7   6   5   4   3   2   1   0
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--  Base+$00 (SPP Data port)    Write Pin:   9   8   7   6   5   4   3   2
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--  Base+$01 (SPP Status port)  Read  Pin: ~11  10  12  13  15   -   -   -                      
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--  Base+$02 (SPP Control port) Write Pin:   -   -   -   - ~17  16 ~14  ~1
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--  Base+$03 (EPP Address port) R/W
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--  Base+$04 (EPP Data port)    R/W
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-- 
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--  ~ indicates a hardware inversion of the bit.
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--  Parallel printer port pin assignment
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-- 
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--  Pin No (DB25) SPP Signal      EPP Signal    Direction Register  Bit Inverted
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--  1             nStrobe         Write_n       Out       Control-0 Yes
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--  2             Data0           Data0         In/Out    Data-0          No
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--  3             Data1           Data1         In/Out    Data-1          No
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--  4             Data2           Data2         In/Out    Data-2          No
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--  5             Data3           Data3         In/Out    Data-3          No
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--  6             Data4           Data4         In/Out    Data-4          No
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--  7             Data5           Data5         In/Out    Data-5          No
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--  8             Data6           Data6         In/Out    Data-6          No
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--  9             Data7           Data7         In/Out    Data-7          No
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--  10            nAck            Interrupt     In        Status-6  No
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--  11            Busy            Wait          In        Status-7  Yes
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--  12            Paper-Out       Spare         In        Status-5  No
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--  13            Select          Spare         In        Status-4  No
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--  14            Linefeed        Data_Strobe_n Out       Control-1 Yes
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--  15            nError          Spare         In        Status-3  No
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--  16            nInitialize     Reset         Out       Control-2 No
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--  17            nSelect-Printer Addr_Strobe_n Out       Control-3 Yes
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--  18-25         Ground          Ground        -         -         -
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-- 
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--  Copyright (C) 2008 - 2010 John Kent
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--
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--  This program is free software: you can redistribute it and/or modify
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--  it under the terms of the GNU General Public License as published by
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--  the Free Software Foundation, either version 3 of the License, or
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--  (at your option) any later version.
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--
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--  This program is distributed in the hope that it will be useful,
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--  but WITHOUT ANY WARRANTY; without even the implied warranty of
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--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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--  GNU General Public License for more details.
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--
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--  You should have received a copy of the GNU General Public License
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--  along with this program.  If not, see <http://www.gnu.org/licenses/>.
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--
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--===========================================================================--
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--                                                                           --
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--                    Revision History                                       --
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--                                                                           --
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--===========================================================================--
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--
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-- Version  Date       Author      Description
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-- 0.1      2008-09-06 John Kent   Initial version generated from ioport.vhd
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-- 0.2      2010-08-09 John Kent   Updated Header and added GPL
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--
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--===========================================================================
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library ieee;
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  use ieee.std_logic_1164.all;
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  use ieee.std_logic_unsigned.all;
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entity spp is
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        port (
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         clk       : in  std_logic;
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    rst       : in  std_logic;
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    cs        : in  std_logic;
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    rw        : in  std_logic;
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    addr      : in  std_logic_vector(2 downto 0);
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    data_in   : in  std_logic_vector(7 downto 0);
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         data_out  : out std_logic_vector(7 downto 0);
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         spp_data  : out std_logic_vector(7 downto 0);
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         spp_stat  : in  std_logic_vector(7 downto 3);
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         spp_ctrl  : out std_logic_vector(3 downto 0);
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         hold      : out std_logic;
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    irq       : out std_logic
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         );
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end;
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architecture rtl of spp is
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signal spp_data_reg : std_logic_vector(7 downto 0);
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signal spp_stat_reg : std_logic_vector(7 downto 3);
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signal spp_ctrl_reg : std_logic_vector(3 downto 0);
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begin
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--------------------------------
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--
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-- read I/O port
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--
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--------------------------------
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spp_read : process( addr,
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                    spp_data_reg, spp_stat_reg, spp_ctrl_reg,
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                                                  spp_stat )
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begin
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      spp_stat_reg(6 downto 3) <=     spp_stat(6 downto 3);
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      spp_stat_reg(7)          <= not spp_stat(7);
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      case addr is
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             when "000" =>
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          data_out <= spp_data_reg;
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                  when "001" =>
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          data_out <= spp_stat_reg & "000";
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             when "010" =>
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                    data_out <= "0000" & spp_ctrl_reg;
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                  when others =>
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                    data_out <= (others=> '0');
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                end case;
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      hold <= '0';
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                irq  <= '0';
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end process;
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---------------------------------
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--
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-- Write I/O ports
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--
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---------------------------------
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spp_write : process( clk, rst, addr, cs, rw, data_in,
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                     spp_data_reg, spp_ctrl_reg )
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begin
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  if clk'event and clk = '0' then
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    if rst = '1' then
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      spp_data_reg <= "00000000";
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      spp_ctrl_reg <= "0000";
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    elsif cs = '1' and rw = '0' then
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      case addr is
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             when "000" =>
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                    spp_data_reg <= data_in;
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                  when "010" =>
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                    spp_ctrl_reg <= data_in(3 downto 0);
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                  when others =>
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                    null;
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                end case;
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         end if;
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  end if;
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  spp_data    <=     spp_data_reg;
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  spp_ctrl(0) <= not spp_ctrl_reg(0);
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  spp_ctrl(1) <= not spp_ctrl_reg(1);
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  spp_ctrl(2) <=     spp_ctrl_reg(2);
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  spp_ctrl(3) <= not spp_ctrl_reg(3);
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end process;
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end rtl;
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