Subversion Repositories altor32

//-----------------------------------------------------------------

//                           AltOR32 

//                Alternative Lightweight OpenRisc 

//                            V2.0

//                     Ultra-Embedded.com

//                   Copyright 2011 - 2013

//

//               Email: admin@ultra-embedded.com

//

//                       License: LGPL

//-----------------------------------------------------------------

//

// Copyright (C) 2011 - 2013 Ultra-Embedded.com

//

// This source file may be used and distributed without         

// restriction provided that this copyright statement is not    

// removed from the file and that any derivative work contains  

// the original copyright notice and the associated disclaimer. 

//

// This source file 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 2.1 of the License, or (at your option) any   

// later version.

//

// This source is distributed in the hope that it will be       

// useful, but WITHOUT ANY WARRANTY; without even the implied   

// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR      

// PURPOSE.  See the GNU Lesser General Public License for more 

// details.

//

// You should have received a copy of the GNU Lesser General    

// Public License along with this source; if not, write to the 

// Free Software Foundation, Inc., 59 Temple Place, Suite 330, 

// Boston, MA  02111-1307  USA

//-----------------------------------------------------------------

//-----------------------------------------------------------------

// Module - Data Cache Memory Interface

//-----------------------------------------------------------------

module altor32_dcache_mem_if

(

    input               clk_i /*verilator public*/,

    input               rst_i /*verilator public*/,

    // Cache interface

    input [31:0]        address_i /*verilator public*/,

    input [31:0]        data_i /*verilator public*/,

    output reg [31:0]   data_o /*verilator public*/,

    input               fill_i /*verilator public*/,

    input               evict_i /*verilator public*/,

    input  [31:0]       evict_addr_i /*verilator public*/,

    input               rd_single_i /*verilator public*/,

    input [3:0]         wr_single_i /*verilator public*/,

    output reg          done_o /*verilator public*/,

    // Cache memory (fill/evict)

    output reg [31:2]   cache_addr_o /*verilator public*/,

    output reg [31:0]   cache_data_o /*verilator public*/,

    input      [31:0]   cache_data_i /*verilator public*/,

    output reg          cache_wr_o /*verilator public*/,

    // Memory interface (slave)

    output reg [31:0]   mem_addr_o /*verilator public*/,

    input  [31:0]       mem_data_i /*verilator public*/,

    output reg [31:0]   mem_data_o /*verilator public*/,

    output reg          mem_burst_o /*verilator public*/,

    output reg          mem_rd_o /*verilator public*/,

    output reg [3:0]    mem_wr_o /*verilator public*/,

    input               mem_accept_i/*verilator public*/,

    input               mem_ack_i/*verilator public*/

);

//-----------------------------------------------------------------

// Params

//-----------------------------------------------------------------

parameter CACHE_LINE_SIZE_WIDTH     = 5;                         /* 5-bits -> 32 entries */

parameter CACHE_LINE_WORDS_IDX_MAX  = CACHE_LINE_SIZE_WIDTH - 2; /* 3-bit -> 8 words */

//-----------------------------------------------------------------

// Registers / Wires

//-----------------------------------------------------------------

reg [31:CACHE_LINE_SIZE_WIDTH]  line_address;

reg [CACHE_LINE_SIZE_WIDTH-3:0] line_word;

// Current state

parameter STATE_IDLE        = 0;

parameter STATE_FETCH       = 1;

parameter STATE_READ_WAIT   = 2;

parameter STATE_WRITE       = 3;

parameter STATE_WRITE_WAIT  = 4;

parameter STATE_READ_SINGLE = 5;

parameter STATE_WRITE_SINGLE= 6;

reg [3:0] state;

//-----------------------------------------------------------------

// Control logic

//-----------------------------------------------------------------

reg [CACHE_LINE_SIZE_WIDTH-3:0] v_line_word;

always @ (posedge rst_i or posedge clk_i )

begin

   if (rst_i == 1'b1)

   begin

        line_address    <= {32-CACHE_LINE_SIZE_WIDTH{1'b0}};

        line_word       <= {CACHE_LINE_SIZE_WIDTH-2{1'b0}};

        mem_addr_o      <= 32'h00000000;

        mem_data_o      <= 32'h00000000;

        mem_wr_o        <= 4'h0;

        mem_rd_o        <= 1'b0;

        mem_burst_o     <= 1'b0;

        cache_addr_o    <= 30'h00000000;

        cache_data_o    <= 32'h00000000;

        cache_wr_o      <= 1'b0;

        done_o          <= 1'b0;

        data_o          <= 32'h00000000;

        state           <= STATE_IDLE;

   end

   else

   begin

        if (mem_accept_i)

        begin

            mem_rd_o        <= 1'b0;

            mem_wr_o        <= 4'h0;

        end

        done_o          <= 1'b0;

        cache_wr_o      <= 1'b0;

        case (state)

            //-----------------------------------------

            // IDLE

            //-----------------------------------------

            STATE_IDLE :

            begin

                // Perform cache evict (write)     

                if (evict_i)

                begin

                    line_address  <= evict_addr_i[31:CACHE_LINE_SIZE_WIDTH];

                    line_word     <= {CACHE_LINE_SIZE_WIDTH-2{1'b0}};

                    // Read data from cache

                    cache_addr_o  <= {evict_addr_i[31:CACHE_LINE_SIZE_WIDTH], {CACHE_LINE_SIZE_WIDTH-2{1'b0}}};

                    state         <= STATE_READ_WAIT;

                end

                // Perform cache fill (read)

                else if (fill_i)

                begin

                    line_address <= address_i[31:CACHE_LINE_SIZE_WIDTH];

                    line_word    <= {CACHE_LINE_SIZE_WIDTH-2{1'b0}};

                    // Start fetch from memory

                    mem_addr_o   <= {address_i[31:CACHE_LINE_SIZE_WIDTH], {CACHE_LINE_SIZE_WIDTH{1'b0}}};

                    mem_rd_o     <= 1'b1;

                    mem_burst_o  <= 1'b1;

                    state        <= STATE_FETCH;

                end

                // Read single

                else if (rd_single_i)

                begin

                    // Start fetch from memory

                    mem_addr_o   <= address_i;

                    mem_data_o   <= 32'b0;

                    mem_rd_o     <= 1'b1;

                    mem_burst_o  <= 1'b0;

                    state        <= STATE_READ_SINGLE;

                end

                // Write single

                else if (|wr_single_i)

                begin

                    // Start fetch from memory

                    mem_addr_o   <= address_i;

                    mem_data_o   <= data_i;

                    mem_wr_o     <= wr_single_i;

                    mem_burst_o  <= 1'b0;

                    state        <= STATE_WRITE_SINGLE;

                end

            end

            //-----------------------------------------

            // FETCH - Fetch line from memory

            //-----------------------------------------

            STATE_FETCH :

            begin

                // Data ready from memory?

                if (mem_ack_i && mem_rd_o == 1'b0)

                begin

                    // Write data into cache

                    cache_addr_o    <= {line_address, line_word};

                    cache_data_o    <= mem_data_i;

                    cache_wr_o      <= 1'b1;

                    // Line fetch complete?

                    if (line_word == {CACHE_LINE_WORDS_IDX_MAX{1'b1}})

                    begin

                        done_o      <= 1'b1;

                        state       <= STATE_IDLE;

                    end

                    // Fetch next word for line

                    else

                    begin

                        v_line_word = line_word + 1'b1;

                        line_word   <= v_line_word;

                        mem_addr_o <= {line_address, v_line_word, 2'b00};

                        mem_rd_o   <= 1'b1;

                        if (line_word == ({CACHE_LINE_WORDS_IDX_MAX{1'b1}}-1))

                        begin

                            mem_burst_o <= 1'b0;

                        end

                    end

                end

            end

            //-----------------------------------------

            // READ_WAIT - Wait for data from cache

            //-----------------------------------------

            STATE_READ_WAIT :

            begin

                // Not used yet, but set for start of burst

                mem_burst_o  <= 1'b1;

                state        <= STATE_WRITE;

            end

            //-----------------------------------------

            // WRITE - Write word to memory

            //-----------------------------------------

            STATE_WRITE :

            begin

                // Write data into memory from cache

                mem_addr_o   <= {line_address, line_word, 2'b00};

                mem_data_o   <= cache_data_i;

                mem_wr_o     <= 4'b1111;

                // Setup next word read from cache

                v_line_word = line_word + 1'b1;

                cache_addr_o <= {line_address, v_line_word};

                state        <= STATE_WRITE_WAIT;

            end

            //-----------------------------------------

            // WRITE_WAIT - Wait for write to complete

            //-----------------------------------------

            STATE_WRITE_WAIT:

            begin

                // Write to memory complete

                if (mem_ack_i && mem_wr_o == 4'b0)

                begin

                    // Line write complete?

                    if (line_word == {CACHE_LINE_WORDS_IDX_MAX{1'b1}})

                    begin

                        done_o      <= 1'b1;

                        state       <= STATE_IDLE;

                    end

                    // Fetch next word for line

                    else

                    begin

                        line_word   <= line_word + 1'b1;

                        state       <= STATE_WRITE;

                        if (line_word == ({CACHE_LINE_WORDS_IDX_MAX{1'b1}}-1))

                            mem_burst_o <= 1'b0;

                    end

                end

            end

            //-----------------------------------------

            // READ_SINGLE - Single access to memory

            //-----------------------------------------

            STATE_READ_SINGLE:

            begin

                // Data ready from memory?

                if (mem_ack_i && mem_rd_o == 1'b0)

                begin

                    data_o      <= mem_data_i;

                    done_o      <= 1'b1;

                    state       <= STATE_IDLE;

                end

            end

            //-----------------------------------------

            // WRITE_SINGLE - Single access to memory

            //-----------------------------------------

            STATE_WRITE_SINGLE:

            begin

                if (mem_ack_i && mem_wr_o == 4'b0)

                begin

                    done_o      <= 1'b1;

                    state       <= STATE_IDLE;

                end

            end

            default:

                ;

           endcase

   end

end

endmodule