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[/] [z80control/] [trunk/] [DE1/] [rtl/] [VHDL/] [t80/] [T80a.vhd] - Blame information for rev 12

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1 12 tylerapohl
--
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-- Z80 compatible microprocessor core, asynchronous top level
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--
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-- Version : 0247
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--
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-- Copyright (c) 2001-2002 Daniel Wallner (jesus@opencores.org)
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--
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-- All rights reserved
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--
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-- Redistribution and use in source and synthezised forms, with or without
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-- modification, are permitted provided that the following conditions are met:
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--
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-- Redistributions of source code must retain the above copyright notice,
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-- this list of conditions and the following disclaimer.
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--
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-- Redistributions in synthesized form must reproduce the above copyright
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-- notice, this list of conditions and the following disclaimer in the
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-- documentation and/or other materials provided with the distribution.
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--
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-- Neither the name of the author nor the names of other contributors may
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-- be used to endorse or promote products derived from this software without
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-- specific prior written permission.
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--
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-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE
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-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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-- POSSIBILITY OF SUCH DAMAGE.
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--
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-- Please report bugs to the author, but before you do so, please
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-- make sure that this is not a derivative work and that
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-- you have the latest version of this file.
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--
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-- The latest version of this file can be found at:
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--      http://www.opencores.org/cvsweb.shtml/t80/
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--
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-- Limitations :
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--
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-- File history :
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--
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--      0208 : First complete release
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--
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--      0211 : Fixed interrupt cycle
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--
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--      0235 : Updated for T80 interface change
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--
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--      0238 : Updated for T80 interface change
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--
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--      0240 : Updated for T80 interface change
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--
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--      0242 : Updated for T80 interface change
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--
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--      0247 : Fixed bus req/ack cycle
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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.numeric_std.all;
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use work.T80_Pack.all;
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entity T80a is
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        generic(
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                Mode : integer := 0      -- 0 => Z80, 1 => Fast Z80, 2 => 8080, 3 => GB
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        );
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        port(
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                RESET_n         : in std_logic;
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                CLK_n           : in std_logic;
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                WAIT_n          : in std_logic;
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                INT_n           : in std_logic;
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                NMI_n           : in std_logic;
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                BUSRQ_n         : in std_logic;
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                M1_n            : out std_logic;
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                MREQ_n          : out std_logic;
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                IORQ_n          : out std_logic;
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                RD_n            : out std_logic;
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                WR_n            : out std_logic;
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                RFSH_n          : out std_logic;
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                HALT_n          : out std_logic;
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                BUSAK_n         : out std_logic;
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                A                       : out std_logic_vector(15 downto 0);
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                D                       : inout std_logic_vector(7 downto 0)
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        );
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end T80a;
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architecture rtl of T80a is
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        signal CEN                      : std_logic;
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        signal Reset_s          : std_logic;
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        signal IntCycle_n       : std_logic;
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        signal IORQ                     : std_logic;
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        signal NoRead           : std_logic;
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        signal Write            : std_logic;
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        signal MREQ                     : std_logic;
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        signal MReq_Inhibit     : std_logic;
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        signal Req_Inhibit      : std_logic;
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        signal RD                       : std_logic;
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        signal MREQ_n_i         : std_logic;
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        signal IORQ_n_i         : std_logic;
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        signal RD_n_i           : std_logic;
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        signal WR_n_i           : std_logic;
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        signal RFSH_n_i         : std_logic;
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        signal BUSAK_n_i        : std_logic;
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        signal A_i                      : std_logic_vector(15 downto 0);
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        signal DO                       : std_logic_vector(7 downto 0);
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        signal DI_Reg           : std_logic_vector (7 downto 0); -- Input synchroniser
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        signal Wait_s           : std_logic;
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        signal MCycle           : std_logic_vector(2 downto 0);
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        signal TState           : std_logic_vector(2 downto 0);
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begin
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        CEN <= '1';
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        BUSAK_n <= BUSAK_n_i;
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        MREQ_n_i <= not MREQ or (Req_Inhibit and MReq_Inhibit);
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        RD_n_i <= not RD or Req_Inhibit;
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        MREQ_n <= MREQ_n_i when BUSAK_n_i = '1' else 'Z';
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        IORQ_n <= IORQ_n_i when BUSAK_n_i = '1' else 'Z';
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        RD_n <= RD_n_i when BUSAK_n_i = '1' else 'Z';
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        WR_n <= WR_n_i when BUSAK_n_i = '1' else 'Z';
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        RFSH_n <= RFSH_n_i when BUSAK_n_i = '1' else 'Z';
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        A <= A_i when BUSAK_n_i = '1' else (others => 'Z');
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        D <= DO when Write = '1' and BUSAK_n_i = '1' else (others => 'Z');
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        process (RESET_n, CLK_n)
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        begin
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                if RESET_n = '0' then
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                        Reset_s <= '0';
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                elsif CLK_n'event and CLK_n = '1' then
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                        Reset_s <= '1';
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                end if;
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        end process;
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        u0 : T80
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                generic map(
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                        Mode => Mode,
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                        IOWait => 1)
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                port map(
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                        CEN => CEN,
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                        M1_n => M1_n,
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                        IORQ => IORQ,
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                        NoRead => NoRead,
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                        Write => Write,
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                        RFSH_n => RFSH_n_i,
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                        HALT_n => HALT_n,
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                        WAIT_n => Wait_s,
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                        INT_n => INT_n,
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                        NMI_n => NMI_n,
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                        RESET_n => Reset_s,
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                        BUSRQ_n => BUSRQ_n,
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                        BUSAK_n => BUSAK_n_i,
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                        CLK_n => CLK_n,
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                        A => A_i,
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                        DInst => D,
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                        DI => DI_Reg,
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                        DO => DO,
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                        MC => MCycle,
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                        TS => TState,
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                        IntCycle_n => IntCycle_n);
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        process (CLK_n)
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        begin
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                if CLK_n'event and CLK_n = '0' then
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                        Wait_s <= WAIT_n;
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                        if TState = "011" and BUSAK_n_i = '1' then
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                                DI_Reg <= to_x01(D);
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                        end if;
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                end if;
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        end process;
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        process (Reset_s,CLK_n)
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        begin
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                if Reset_s = '0' then
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                        WR_n_i <= '1';
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                elsif CLK_n'event and CLK_n = '1' then
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                        WR_n_i <= '1';
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                        if TState = "001" then  -- To short for IO writes !!!!!!!!!!!!!!!!!!!
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                                WR_n_i <= not Write;
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                        end if;
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                end if;
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        end process;
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        process (Reset_s,CLK_n)
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        begin
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                if Reset_s = '0' then
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                        Req_Inhibit <= '0';
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                elsif CLK_n'event and CLK_n = '1' then
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                        if MCycle = "001" and TState = "010" then
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                                Req_Inhibit <= '1';
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                        else
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                                Req_Inhibit <= '0';
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                        end if;
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                end if;
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        end process;
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        process (Reset_s,CLK_n)
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        begin
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                if Reset_s = '0' then
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                        MReq_Inhibit <= '0';
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                elsif CLK_n'event and CLK_n = '0' then
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                        if MCycle = "001" and TState = "010" then
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                                MReq_Inhibit <= '1';
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                        else
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                                MReq_Inhibit <= '0';
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                        end if;
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                end if;
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        end process;
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        process(Reset_s,CLK_n)
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        begin
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                if Reset_s = '0' then
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                        RD <= '0';
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                        IORQ_n_i <= '1';
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                        MREQ <= '0';
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                elsif CLK_n'event and CLK_n = '0' then
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                        if MCycle = "001" then
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                                if TState = "001" then
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                                        RD <= IntCycle_n;
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                                        MREQ <= IntCycle_n;
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                                        IORQ_n_i <= IntCycle_n;
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                                end if;
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                                if TState = "011" then
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                                        RD <= '0';
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                                        IORQ_n_i <= '1';
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                                        MREQ <= '1';
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                                end if;
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                                if TState = "100" then
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                                        MREQ <= '0';
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                                end if;
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                        else
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                                if TState = "001" and NoRead = '0' then
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                                        RD <= not Write;
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                                        IORQ_n_i <= not IORQ;
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                                        MREQ <= not IORQ;
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                                end if;
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                                if TState = "011" then
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                                        RD <= '0';
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                                        IORQ_n_i <= '1';
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                                        MREQ <= '0';
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                                end if;
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                        end if;
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                end if;
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        end process;
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end;

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