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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