Subversion Repositories t48

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--

-- The Wishbone master module.

--

-- $Id: wb_master.vhd,v 1.3 2005-05-08 10:36:07 arniml Exp $

--

-- Copyright (c) 2005, Arnim Laeuger (arniml@opencores.org)

--

-- All rights reserved

--

-- Redistribution and use in source and synthezised forms, with or without

-- modification, are permitted provided that the following conditions are met:

--

-- Redistributions of source code must retain the above copyright notice,

-- this list of conditions and the following disclaimer.

--

-- Redistributions in synthesized form must reproduce the above copyright

-- notice, this list of conditions and the following disclaimer in the

-- documentation and/or other materials provided with the distribution.

--

-- Neither the name of the author nor the names of other contributors may

-- be used to endorse or promote products derived from this software without

-- specific prior written permission.

--

-- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

-- AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,

-- THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

-- PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE

-- LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

-- CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

-- SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

-- INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

-- CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

-- ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

-- POSSIBILITY OF SUCH DAMAGE.

--

-- Please report bugs to the author, but before you do so, please

-- make sure that this is not a derivative work and that

-- you have the latest version of this file.

--

-- The latest version of this file can be found at:

--      http://www.opencores.org/cvsweb.shtml/t48/

--

--

-- Short description:

--   This design implements a simple Wishbone bus master. It connects to the

--   BUS interface of the T48 uController core.

--

--   The CPU clock is suppressed with en_clk_o to stall the CPU until the

--   acknowledge signal from the peripheral is detected.

--

--   The adr_i input selects between configuration and Wishbone address range:

--     1 - configuration range

--     0 - Wishbone range

--

--   When configuration range is selected, two address register are accessible.

--     000h -> adr1

--     001h -> adr2

--   These registers can be read and written with movx to their addresses.

--

--   When Wishbone range is selected, all movx generate Wishbone bus cycles

--   (either read or write) at following address:

--     Wishbone address = adr2 & adr1 & address of movx

--

-------------------------------------------------------------------------------

library ieee;

use ieee.std_logic_1164.all;

use work.t48_pack.all;

entity wb_master is

  port (

    xtal_i   : in  std_logic;

    res_i    : in  std_logic;

    en_clk_o : out std_logic;

    -- T48 Interface ----------------------------------------------------------

    ale_i    : in  std_logic;

    rd_n_i   : in  std_logic;

    wr_n_i   : in  std_logic;

    adr_i    : in  std_logic;

    db_bus_i : in  std_logic_vector( 7 downto 0);

    db_bus_o : out std_logic_vector( 7 downto 0);

    -- Wishbone Interface -----------------------------------------------------

    wb_cyc_o : out std_logic;

    wb_stb_o : out std_logic;

    wb_we_o  : out std_logic;

    wb_adr_o : out std_logic_vector(23 downto 0);

    wb_ack_i : in  std_logic;

    wb_dat_i : in  std_logic_vector( 7 downto 0);

    wb_dat_o : out std_logic_vector( 7 downto 0)

  );

end wb_master;

architecture rtl of wb_master is

  -----------------------------------------------------------------------------

  -- Controller FSM

  -----------------------------------------------------------------------------

  type   state_t is (IDLE, CYC, WAIT_INACT);

  signal state_s,

         state_q  : state_t;

  -----------------------------------------------------------------------------

  -- Select signals for each range

  -----------------------------------------------------------------------------

  signal sel_adr1_s,

         sel_adr2_s,

         sel_wb_s   : boolean;

  signal wr_s,

         rd_s       : boolean;

  signal adr_q : std_logic_vector(23 downto 0);

begin

  -----------------------------------------------------------------------------

  -- Select signal generation

  -----------------------------------------------------------------------------

  sel_adr1_s <= adr_i = '1' and adr_q(word_t'range) = "00000000";

  sel_adr2_s <= adr_i = '1' and adr_q(word_t'range) = "00000001";

  sel_wb_s   <= adr_i = '0';

  wr_s      <= wr_n_i = '0';

  rd_s      <= rd_n_i = '0';

  -----------------------------------------------------------------------------

  -- Process seq

  --

  -- Purpose:

  --   Implements the sequential elements.

  --

  seq: process (res_i, xtal_i)

  begin

    if res_i = res_active_c then

      adr_q   <= (others => '0');

      state_q <= IDLE;

    elsif xtal_i'event and xtal_i = clk_active_c then

      -- Address register -----------------------------------------------------

      -- update lowest address byte

      if ale_i = '1' then

        adr_q(word_t'range) <= db_bus_i;

      end if;

      -- set adr1 part

      if wr_s and sel_adr1_s then

        adr_q(word_t'length*2 - 1 downto word_t'length) <= db_bus_i;

      end if;

      -- set adr2 part

      if wr_s and sel_adr2_s then

        adr_q(word_t'length*3 - 1 downto word_t'length*2) <= db_bus_i;

      end if;

      -- FSM state ------------------------------------------------------------

      state_q <= state_s;

    end if;

  end process seq;

  --

  -----------------------------------------------------------------------------

  -----------------------------------------------------------------------------

  -- Process fsm

  --

  -- Purpose:

  --   Implements the state transitions of the controller FSM.

  --

  fsm: process (state_q,

                wr_s,

                rd_s,

                sel_wb_s,

                wb_ack_i)

  begin

    -- default assignments

    wb_cyc_o <= '0';

    wb_stb_o <= '0';

    en_clk_o <= '1';

    state_s  <= IDLE;

    case state_q is

      -- Idle State: Wait for read or write access ----------------------------

      when IDLE =>

        if sel_wb_s and (wr_s or rd_s) then

          state_s <= CYC;

        end if;

      -- WB Cycle State: Start Wishbone cycle and wait for ack ----------------

      when CYC =>

        wb_cyc_o <= '1';

        wb_stb_o <= '1';

        en_clk_o <= '0';

        if wb_ack_i = '1' then

          state_s <= WAIT_INACT;

        else

          state_s <= CYC;

        end if;

      -- Wait inact State: Wait for end of T48 access -------------------------

      when WAIT_INACT =>

        if not wr_s and not rd_s then

          state_s <= IDLE;

        else

          state_s <= WAIT_INACT;

        end if;

      when others =>

        null;

    end case;

  end process fsm;

  --

  -----------------------------------------------------------------------------

  -----------------------------------------------------------------------------

  --  Output multiplexer

  -----------------------------------------------------------------------------

  db_bus_o <=   adr_q(word_t'length*2 - 1 downto word_t'length)

              when sel_adr1_s else

                adr_q(word_t'length*3 - 1 downto word_t'length*2)

              when sel_adr2_s else

                wb_dat_i;

  -----------------------------------------------------------------------------

  -- Output mapping

  -----------------------------------------------------------------------------

  wb_adr_o <= adr_q;

  wb_dat_o <= db_bus_i;

  wb_we_o  <=   '1'

              when wr_s else

                '0';

end rtl;

-------------------------------------------------------------------------------

-- File History:

--

-- $Log: not supported by cvs2svn $

-- Revision 1.2  2005/05/06 18:54:03  arniml

-- assign default for state_s

--

-- Revision 1.1  2005/05/05 19:49:03  arniml

-- initial check-in

--

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