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////  WISHBONE Memory Controller                                 ////

////  WISHBONE Interface                                         ////

////                                                             ////

////                                                             ////

////  Author: Rudolf Usselmann                                   ////

////          rudi@asics.ws                                      ////

////                                                             ////

////                                                             ////

////  Downloaded from: http://www.opencores.org/cores/mem_ctrl/  ////

////                                                             ////

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////                                                             ////

//// Copyright (C) 2000-2002 Rudolf Usselmann                    ////

////                         www.asics.ws                        ////

////                         rudi@asics.ws                       ////

////                                                             ////

//// 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 SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY     ////

//// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED   ////

//// TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS   ////

//// FOR A PARTICULAR PURPOSE. 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.                                 ////

////                                                             ////

/////////////////////////////////////////////////////////////////////

//  CVS Log

//

//  $Id: mc_wb_if.v,v 1.6 2002-01-21 13:08:52 rudi Exp $

//

//  $Date: 2002-01-21 13:08:52 $

//  $Revision: 1.6 $

//  $Author: rudi $

//  $Locker:  $

//  $State: Exp $

//

// Change History:

//               $Log: not supported by cvs2svn $

//               Revision 1.5  2001/12/11 02:47:19  rudi

//

//               - Made some changes not to expect clock during reset ...

//

//               Revision 1.4  2001/11/29 02:16:28  rudi

//

//

//               - More Synthesis cleanup, mostly for speed

//               - Several bug fixes

//               - Changed code to avoid auto-precharge and

//                 burst-terminate combinations (apparently illegal ?)

//                 Now we will do a manual precharge ...

//

//               Revision 1.3  2001/09/24 00:38:21  rudi

//

//               Changed Reset to be active high and async.

//

//               Revision 1.2  2001/08/10 08:16:21  rudi

//

//               - Changed IO names to be more clear.

//               - Uniquifyed define names to be core specific.

//               - Removed "Refresh Early" configuration

//

//               Revision 1.1  2001/07/29 07:34:41  rudi

//

//

//               1) Changed Directory Structure

//               2) Fixed several minor bugs

//

//               Revision 1.3  2001/06/12 15:19:49  rudi

//

//

//              Minor changes after running lint, and a small bug

//              fix reading csr and ba_mask registers.

//

//               Revision 1.2  2001/06/03 11:37:17  rudi

//

//

//               1) Fixed Chip Select Mask Register

//                      - Power On Value is now all ones

//                      - Comparison Logic is now correct

//

//               2) All resets are now asynchronous

//

//               3) Converted Power On Delay to an configurable item

//

//               4) Added reset to Chip Select Output Registers

//

//               5) Forcing all outputs to Hi-Z state during reset

//

//               Revision 1.1.1.1  2001/05/13 09:39:47  rudi

//               Created Directory Structure

//

//

//

//

`include "mc_defines.v"

module mc_wb_if(clk, rst,

                wb_addr_i, wb_cyc_i, wb_stb_i, wb_we_i, wb_err, wb_ack_o,

                wb_read_go, wb_write_go,

                wb_first, wb_wait, mem_ack, wr_hold,

                err, par_err, wp_err,

                wb_data_o, mem_dout, rf_dout);

input           clk, rst;

input   [31:0]   wb_addr_i;

input           wb_cyc_i;

input           wb_stb_i;

input           wb_we_i;

output          wb_err;

output          wb_ack_o;

output          wb_read_go;

output          wb_write_go;

output          wb_first;

output          wb_wait;

input           mem_ack;

output          wr_hold;

input           err, par_err, wp_err;

output  [31:0]   wb_data_o;

input   [31:0]   mem_dout, rf_dout;

////////////////////////////////////////////////////////////////////

//

// Local Wires and Registers

//

wire            mem_sel;

reg             read_go_r;

reg             read_go_r1;

reg             write_go_r;

reg             write_go_r1;

reg             wb_first_r;

wire            wb_first_set;

reg             wr_hold;

wire            rmw;

reg             rmw_r;

reg             rmw_en;

reg             wb_ack_o;

reg             wb_err;

reg     [31:0]   wb_data_o;

////////////////////////////////////////////////////////////////////

//

// Memory Go Logic

//

assign mem_sel = `MC_MEM_SEL;

always @(posedge clk or posedge rst)

        if(rst)                 rmw_en <= #1 1'b0;

        else

        if(wb_ack_o)            rmw_en <= #1 1'b1;

        else

        if(!wb_cyc_i)           rmw_en <= #1 1'b0;

always @(posedge clk or posedge rst)

        if(rst) rmw_r <= #1 1'b0;

        else    rmw_r <= #1 !wr_hold & wb_we_i & wb_cyc_i & wb_stb_i & rmw_en;

assign rmw = rmw_r | (!wr_hold & wb_we_i & wb_cyc_i & wb_stb_i & rmw_en);

always @(posedge clk or posedge rst)

        if(rst) read_go_r1 <= #1 1'b0;

        else    read_go_r1 <= #1 !rmw & wb_cyc_i &

                                ((wb_stb_i & mem_sel & !wb_we_i) | read_go_r);

always @(posedge clk or posedge rst)

        if(rst) read_go_r <= #1 1'b0;

        else    read_go_r <= #1 read_go_r1 & wb_cyc_i;

assign  wb_read_go = !rmw & read_go_r1 & wb_cyc_i;

always @(posedge clk or posedge rst)

        if(rst) write_go_r1 <= #1 1'b0;

        else    write_go_r1 <= #1 wb_cyc_i &

                                ((wb_stb_i & mem_sel & wb_we_i) | write_go_r);

always @(posedge clk or posedge rst)

        if(rst)         write_go_r <= #1 1'b0;

        else            write_go_r <= #1 write_go_r1 & wb_cyc_i &

                                        ((wb_we_i & wb_stb_i) | !wb_stb_i);

assign wb_write_go =    !rmw & write_go_r1 & wb_cyc_i &

                        ((wb_we_i & wb_stb_i) | !wb_stb_i);

assign wb_first_set = mem_sel & wb_cyc_i & wb_stb_i & !(read_go_r | write_go_r);

assign wb_first = wb_first_set | (wb_first_r & !wb_ack_o & !wb_err);

always @(posedge clk or posedge rst)

        if(rst)                 wb_first_r <= #1 1'b0;

        else

        if(wb_first_set)        wb_first_r <= #1 1'b1;

        else

        if(wb_ack_o | wb_err)   wb_first_r <= #1 1'b0;

always @(posedge clk or posedge rst)

        if(rst)                 wr_hold <= #1 1'b0;

        else

        if(wb_cyc_i & wb_stb_i) wr_hold <= #1 wb_we_i;

////////////////////////////////////////////////////////////////////

//

// WB Ack

//

wire    wb_err_d;

// Ack no longer asserted when wb_err is asserted

always @(posedge clk or posedge rst)

        if(rst) wb_ack_o <= #1 1'b0;

        else    wb_ack_o <= #1 `MC_MEM_SEL ? mem_ack & !wb_err_d :

                                `MC_REG_SEL & wb_cyc_i & wb_stb_i & !wb_ack_o;

assign wb_err_d = wb_cyc_i & wb_stb_i & (par_err | err | wp_err);

always @(posedge clk or posedge rst)

        if(rst) wb_err <= #1 1'b0;

        else    wb_err <= #1 `MC_MEM_SEL & wb_err_d & !wb_err;

////////////////////////////////////////////////////////////////////

//

// Memory Wait Logic

//

assign wb_wait = wb_cyc_i & !wb_stb_i & (wb_write_go | wb_read_go);

////////////////////////////////////////////////////////////////////

//

// WISHBONE Data Output

//

always @(posedge clk)

        wb_data_o <= #1 `MC_MEM_SEL ? mem_dout : rf_dout;

endmodule