Subversion Repositories core_arm

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

--  This file is a part of the LEON VHDL model

--  Copyright (C) 1999  European Space Agency (ESA)

--

--  This library is free software; you can redistribute it and/or

--  modify it under the terms of the GNU Lesser General Public

--  License as published by the Free Software Foundation; either

--  version 2 of the License, or (at your option) any later version.

--

--  See the file COPYING.LGPL for the full details of the license.

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

-- Entity:      ahbmst

-- File:        ahbmst.vhd

-- Author:      Jiri Gaisler - Gaisler Research

-- Description: Simple AHB master interface

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

library IEEE;

use IEEE.std_logic_1164.all;

use IEEE.std_logic_unsigned."+";

use IEEE.std_logic_arith.conv_unsigned;

use work.amba.all;

use work.leon_iface.all;

use work.macro.all;

entity ahbmst is

  generic (incaddr : integer := 0);

   port (

      rst  : in  std_logic;

      clk  : in  clk_type;

      dmai : in ahb_dma_in_type;

      dmao : out ahb_dma_out_type;

      ahbi : in  ahb_mst_in_type;

      ahbo : out ahb_mst_out_type

      );

end;

architecture rtl of ahbmst is

type reg_type is record

  start   : std_logic;

  retry   : std_logic;

  grant   : std_logic;

  active  : std_logic;

end record;

signal r, rin : reg_type;

begin

  comb : process(ahbi, dmai, rst, r)

  variable v       : reg_type;

  variable ready   : std_logic;

  variable retry   : std_logic;

  variable mexc    : std_logic;

  variable inc     : std_logic_vector(3 downto 0);    -- address increment

  variable haddr   : std_logic_vector(31 downto 0);   -- AHB address

  variable hwdata  : std_logic_vector(31 downto 0);   -- AHB write data

  variable htrans  : std_logic_vector(1 downto 0);    -- transfer type 

  variable hwrite  : std_logic;                       -- read/write

  variable hburst  : std_logic_vector(2 downto 0);    -- burst type

  variable newaddr : std_logic_vector(9 downto 0); -- next sequential address

  variable hbusreq : std_logic;   -- bus request

  begin

    v := r; ready := '0'; mexc := '0'; retry := '0';

    haddr := dmai.address; hbusreq := dmai.start; hwdata := dmai.wdata;

    newaddr := dmai.address(9 downto 0);

    inc := decode(dmai.size);

    if incaddr > 0 then

-- pragma translate_off

      if not is_x(haddr(9 downto 0)) then

-- pragma translate_on

        newaddr := haddr(9 downto 0) + inc(2 downto 0);

-- pragma translate_off

      end if;

-- pragma translate_on

    end if;

    if dmai.burst = '1' then hburst := HBURST_INCR;

    else hburst := HBURST_SINGLE; end if;

    if dmai.start = '1' then

      if (r.active and dmai.burst and not r.retry) = '1' then

        htrans := HTRANS_SEQ; hburst := HBURST_INCR;

        haddr(9 downto 0) := newaddr;

      else htrans := HTRANS_NONSEQ; end if;

    else htrans := HTRANS_IDLE; end if;

    if r.active = '1' then

      if ahbi.hready = '1' then

        case ahbi.hresp is

        when HRESP_OKAY => ready := '1';

        when HRESP_RETRY | HRESP_SPLIT=> retry := '1';

        when others => ready := '1'; mexc := '1';

        end case;

      end if;

      if ((ahbi.hresp = HRESP_RETRY) or (ahbi.hresp = HRESP_SPLIT)) then

        v.retry := not ahbi.hready;

      else v.retry := '0'; end if;

    end if;

    if r.retry = '1' then htrans := HTRANS_IDLE; end if;

    v.start := '0';

    if ahbi.hready = '1' then

      v.grant := ahbi.hgrant;

      if (htrans = HTRANS_NONSEQ) or (htrans = HTRANS_SEQ) then

        v.active := r.grant; v.start := r.grant;

      else

        v.active := '0';

      end if;

    end if;

    if rst = '0' then v.retry := '0'; v.active := '0'; end if;

    rin <= v;

    ahbo.haddr   <= haddr;

    ahbo.htrans  <= htrans;

    ahbo.hbusreq <= hbusreq;

    ahbo.hwdata  <= dmai.wdata;

    ahbo.hlock   <= '0';

    ahbo.hwrite  <= dmai.write;

    ahbo.hsize   <= '0' & dmai.size;

    ahbo.hburst  <= hburst;

    ahbo.hprot   <= "0011";     -- non-cached supervisor data

    dmao.start   <= r.start;

    dmao.active  <= r.active;

    dmao.ready   <= ready;

    dmao.mexc    <= mexc;

    dmao.retry   <= retry;

    dmao.haddr   <= newaddr;

    dmao.rdata   <= ahbi.hrdata;

  end process;

    regs : process(clk)

    begin if rising_edge(clk) then r <= rin; end if; end process;

end;