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///////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////
//
//
// Filename:    memops.v
// Filename:    memops.v
//
//
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
// Project:     Zip CPU -- a small, lightweight, RISC CPU soft core
//
//
// Purpose:     A memory unit to support a CPU.
// Purpose:     A memory unit to support a CPU.
//
//
//      In the interests of code simplicity, this memory operator is 
//      In the interests of code simplicity, this memory operator is 
//      susceptible to unknown results should a new command be sent to it
//      susceptible to unknown results should a new command be sent to it
//      before it completes the last one.  Unpredictable results might then
//      before it completes the last one.  Unpredictable results might then
//      occurr.
//      occurr.
//
//
//      20150919 -- Added support for handling BUS ERR's (i.e., the WB
//      20150919 -- Added support for handling BUS ERR's (i.e., the WB
//              error signal).
//              error signal).
//
//
// Creator:     Dan Gisselquist, Ph.D.
// Creator:     Dan Gisselquist, Ph.D.
//              Gisselquist Tecnology, LLC
//              Gisselquist Tecnology, LLC
//
//
///////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////
//
//
// Copyright (C) 2015, Gisselquist Technology, LLC
// Copyright (C) 2015, Gisselquist Technology, LLC
//
//
// This program is free software (firmware): you can redistribute it and/or
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of  the GNU General Public License as published
// modify it under the terms of  the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
// your option) any later version.
//
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
// for more details.
//
//
// License:     GPL, v3, as defined and found on www.gnu.org,
// License:     GPL, v3, as defined and found on www.gnu.org,
//              http://www.gnu.org/licenses/gpl.html
//              http://www.gnu.org/licenses/gpl.html
//
//
//
//
///////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////
//
//
module  memops(i_clk, i_rst, i_stb,
module  memops(i_clk, i_rst, i_stb,
                i_op, i_addr, i_data, i_oreg,
                i_op, i_addr, i_data, i_oreg,
                        o_busy, o_valid, o_err, o_wreg, o_result,
                        o_busy, o_valid, o_err, o_wreg, o_result,
                o_wb_cyc_gbl, o_wb_cyc_lcl,
                o_wb_cyc_gbl, o_wb_cyc_lcl,
                        o_wb_stb_gbl, o_wb_stb_lcl,
                        o_wb_stb_gbl, o_wb_stb_lcl,
                        o_wb_we, o_wb_addr, o_wb_data,
                        o_wb_we, o_wb_addr, o_wb_data,
                i_wb_ack, i_wb_stall, i_wb_err, i_wb_data);
                i_wb_ack, i_wb_stall, i_wb_err, i_wb_data);
 
        parameter       ADDRESS_WIDTH=24, AW=ADDRESS_WIDTH;
        input                   i_clk, i_rst;
        input                   i_clk, i_rst;
        input                   i_stb;
        input                   i_stb;
        // CPU interface
        // CPU interface
        input                   i_op;
        input                   i_op;
        input           [31:0]   i_addr;
        input           [31:0]   i_addr;
        input           [31:0]   i_data;
        input           [31:0]   i_data;
        input           [4:0]    i_oreg;
        input           [4:0]    i_oreg;
        // CPU outputs
        // CPU outputs
        output  wire            o_busy;
        output  wire            o_busy;
        output  reg             o_valid;
        output  reg             o_valid;
        output  reg             o_err;
        output  reg             o_err;
        output  reg     [4:0]    o_wreg;
        output  reg     [4:0]    o_wreg;
        output  reg     [31:0]   o_result;
        output  reg     [31:0]   o_result;
        // Wishbone outputs
        // Wishbone outputs
        output  reg             o_wb_cyc_gbl, o_wb_stb_gbl;
        output  reg             o_wb_cyc_gbl, o_wb_stb_gbl;
        output  reg             o_wb_cyc_lcl, o_wb_stb_lcl, o_wb_we;
        output  reg             o_wb_cyc_lcl, o_wb_stb_lcl, o_wb_we;
        output  reg     [31:0]   o_wb_addr, o_wb_data;
        output  reg     [(AW-1):0]       o_wb_addr;
 
        output  reg     [31:0]   o_wb_data;
        // Wishbone inputs
        // Wishbone inputs
        input                   i_wb_ack, i_wb_stall, i_wb_err;
        input                   i_wb_ack, i_wb_stall, i_wb_err;
        input           [31:0]   i_wb_data;
        input           [31:0]   i_wb_data;
 
 
        wire    gbl_stb, lcl_stb;
        wire    gbl_stb, lcl_stb;
        assign  lcl_stb = (i_stb)&&(i_addr[31:8]==24'hc00000)&&(i_addr[7:5]==3'h0);
        assign  lcl_stb = (i_stb)&&(i_addr[31:8]==24'hc00000)&&(i_addr[7:5]==3'h0);
        assign  gbl_stb = (i_stb)&&((i_addr[31:8]!=24'hc00000)||(i_addr[7:5]!=3'h0));
        assign  gbl_stb = (i_stb)&&((i_addr[31:8]!=24'hc00000)||(i_addr[7:5]!=3'h0));
 
 
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_rst)
                if (i_rst)
                begin
                begin
                        o_wb_cyc_gbl <= 1'b0;
                        o_wb_cyc_gbl <= 1'b0;
                        o_wb_cyc_lcl <= 1'b0;
                        o_wb_cyc_lcl <= 1'b0;
                end else if ((o_wb_cyc_gbl)||(o_wb_cyc_lcl))
                end else if ((o_wb_cyc_gbl)||(o_wb_cyc_lcl))
                begin
                begin
                        if ((i_wb_ack)||(i_wb_err))
                        if ((i_wb_ack)||(i_wb_err))
                        begin
                        begin
                                o_wb_cyc_gbl <= 1'b0;
                                o_wb_cyc_gbl <= 1'b0;
                                o_wb_cyc_lcl <= 1'b0;
                                o_wb_cyc_lcl <= 1'b0;
                        end
                        end
                end else if (i_stb) // New memory operation
                end else if (i_stb) // New memory operation
                begin // Grab the wishbone
                begin // Grab the wishbone
                        o_wb_cyc_lcl <= lcl_stb;
                        o_wb_cyc_lcl <= lcl_stb;
                        o_wb_cyc_gbl <= gbl_stb;
                        o_wb_cyc_gbl <= gbl_stb;
                end
                end
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (o_wb_cyc_gbl)
                if (o_wb_cyc_gbl)
                        o_wb_stb_gbl <= (o_wb_stb_gbl)&&(i_wb_stall);
                        o_wb_stb_gbl <= (o_wb_stb_gbl)&&(i_wb_stall);
                else
                else
                        o_wb_stb_gbl <= gbl_stb; // Grab wishbone on new operation
                        o_wb_stb_gbl <= gbl_stb; // Grab wishbone on new operation
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (o_wb_cyc_lcl)
                if (o_wb_cyc_lcl)
                        o_wb_stb_lcl <= (o_wb_stb_lcl)&&(i_wb_stall);
                        o_wb_stb_lcl <= (o_wb_stb_lcl)&&(i_wb_stall);
                else
                else
                        o_wb_stb_lcl  <= lcl_stb; // Grab wishbone on new operation
                        o_wb_stb_lcl  <= lcl_stb; // Grab wishbone on new operation
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_stb)
                if (i_stb)
                begin
                begin
                        o_wb_we   <= i_op;
                        o_wb_we   <= i_op;
                        o_wb_data <= i_data;
                        o_wb_data <= i_data;
                        o_wb_addr <= i_addr;
                        o_wb_addr <= i_addr[(AW-1):0];
                end
                end
 
 
        initial o_valid = 1'b0;
        initial o_valid = 1'b0;
        always @(posedge i_clk)
        always @(posedge i_clk)
                o_valid <= ((o_wb_cyc_gbl)||(o_wb_cyc_lcl))&&(i_wb_ack)&&(~o_wb_we);
                o_valid <= ((o_wb_cyc_gbl)||(o_wb_cyc_lcl))&&(i_wb_ack)&&(~o_wb_we);
        initial o_err = 1'b0;
        initial o_err = 1'b0;
        always @(posedge i_clk)
        always @(posedge i_clk)
                o_err <= ((o_wb_cyc_gbl)||(o_wb_cyc_lcl))&&(i_wb_err);
                o_err <= ((o_wb_cyc_gbl)||(o_wb_cyc_lcl))&&(i_wb_err);
        assign  o_busy = (o_wb_cyc_gbl)||(o_wb_cyc_lcl);
        assign  o_busy = (o_wb_cyc_gbl)||(o_wb_cyc_lcl);
 
 
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_stb)
                if (i_stb)
                        o_wreg    <= i_oreg;
                        o_wreg    <= i_oreg;
        always @(posedge i_clk)
        always @(posedge i_clk)
                if (i_wb_ack)
                if (i_wb_ack)
                        o_result <= i_wb_data;
                        o_result <= i_wb_data;
endmodule
endmodule
 
 

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