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

//

// Filename:    gpsclock_tb.v

//              

// Project:     A GPS Schooled Clock Core

//

// Purpose:     Provide a test bench, internal to an FPGA, whereby the GPS

//              clock module can be tested.

//

//

// Creator:     Dan Gisselquist, Ph.D.

//              Gisselquist Technology, LLC

//

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

//

// Copyright (C) 2015-2016, Gisselquist Technology, LLC

//

// 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

// by the Free Software Foundation, either version 3 of the License, or (at

// your option) any later version.

//

// This program is distributed in the hope that it will be useful, but WITHOUT

// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or

// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

// for more details.

//

// You should have received a copy of the GNU General Public License along

// with this program.  (It's in the $(ROOT)/doc directory.  Run make with no

// target there if the PDF file isn't present.)  If not, see

// <http://www.gnu.org/licenses/> for a copy.

//

// License:     GPL, v3, as defined and found on www.gnu.org,

//              http://www.gnu.org/licenses/gpl.html

//

//

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

module  gpsclock_tb(i_clk, i_lcl_pps, o_pps,

                i_wb_cyc_stb, i_wb_we, i_wb_addr, i_wb_data,

                        o_wb_ack, o_wb_stall, o_wb_data,

                i_err, i_count, i_step);

        parameter       DW=32, RW=64;

        input                           i_clk, i_lcl_pps;

        output  reg                     o_pps;  // To our local circuitry

        // Wishbone Configuration interface

        input                           i_wb_cyc_stb, i_wb_we;

        input           [2:0]            i_wb_addr;

        input           [(DW-1):0]       i_wb_data;

        output  reg                     o_wb_ack;

        output  wire                    o_wb_stall;

        output  reg     [(DW-1):0]       o_wb_data;

        // Status and timing outputs

        input   [(RW-1):0]       i_err, // Fraction of a second err

                                i_count, // Fraction of a second

                                i_step; // 2^RW / clock speed (in Hz)

        reg     [31:0]   r_jump, r_maxcount;

        reg             r_halt;

        //

        //

        //

        // Wishbone access ...

        //

        //

        //

        initial r_jump = 0;

        initial r_maxcount = 32'd81200000;

        always @(posedge i_clk)

                if ((i_wb_cyc_stb)&&(i_wb_we))

                begin

                        case(i_wb_addr)

                        3'b000: r_maxcount <= i_wb_data;

                        3'b001: r_jump     <= i_wb_data;

                        // 2'b11: r_def_step <= i_wb_data;

                        default: begin end

                        // r_defstep <= i_wb_data;

                        endcase

                end else

                        r_jump <= 32'h00;

        reg     [31:0]   r_err, r_lcl;

        reg     [63:0]   r_count, r_step;

        initial r_lcl = 32'h000;

        initial r_halt = 1'b0;

        always @(posedge i_clk)

                case (i_wb_addr)

                        3'b000: o_wb_data <= r_maxcount;

                        3'b001: begin o_wb_data <= r_lcl; r_halt <= 1'b1; end // { 31'h00, r_halt };

                        3'b010: begin o_wb_data <= i_err[63:32]; r_halt <= 1'b1; end

                        3'b011: o_wb_data <= r_err[31:0];

                        3'b100: o_wb_data <= r_count[63:32];

                        3'b101: o_wb_data <= r_count[31:0];

                        3'b110: o_wb_data <= r_step[63:32];

                        3'b111: begin o_wb_data <= r_step[31:0]; r_halt <= 1'b0; end

                        // default: o_wb_data <= 0;

                endcase

        always @(posedge i_clk)

                o_wb_ack <= i_wb_cyc_stb;

        assign  o_wb_stall = 1'b0;

        //

        //

        // Generate a PPS signal

        //

        //

        reg     [31:0]   r_ctr;

        always @(posedge i_clk)

                if (r_ctr >= r_maxcount-1)

                        r_ctr <= r_ctr+1-r_maxcount+r_jump;

                else

                        r_ctr <= r_ctr+1+r_jump;

        always @(posedge i_clk)

                if (r_ctr >= r_maxcount-1)

                        o_pps <= 1'b1;

                else

                        o_pps <= 1'b0;

        reg     [31:0]   lcl_counter;

        always @(posedge i_clk)

                lcl_counter <= lcl_counter + 32'h001;

        always @(posedge i_clk)

                if ((~r_halt)&&(i_lcl_pps))

                begin

                        r_err   <= i_err[31:0];

                        r_count <= i_count;

                        r_step  <= i_step;

                        r_lcl   <= lcl_counter;

                end

endmodule