135 lines
5.3 KiB
Verilog
135 lines
5.3 KiB
Verilog
//////////////////////////////////////////////////////////////////////
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//// ////
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//// eth_clockgen.v ////
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//// ////
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//// This file is part of the Ethernet IP core project ////
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//// http://www.opencores.org/projects/ethmac/ ////
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//// ////
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//// Author(s): ////
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//// - Igor Mohor (igorM@opencores.org) ////
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//// ////
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//// All additional information is avaliable in the Readme.txt ////
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//// file. ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//// ////
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//// Copyright (C) 2001 Authors ////
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//// ////
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//// This source file may be used and distributed without ////
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//// restriction provided that this copyright statement is not ////
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//// removed from the file and that any derivative work contains ////
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//// the original copyright notice and the associated disclaimer. ////
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//// ////
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//// This source file is free software; you can redistribute it ////
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//// and/or modify it under the terms of the GNU Lesser General ////
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//// Public License as published by the Free Software Foundation; ////
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//// either version 2.1 of the License, or (at your option) any ////
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//// later version. ////
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//// ////
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//// This source is distributed in the hope that it will be ////
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//// useful, but WITHOUT ANY WARRANTY; without even the implied ////
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//// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////
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//// PURPOSE. See the GNU Lesser General Public License for more ////
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//// details. ////
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//// ////
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//// You should have received a copy of the GNU Lesser General ////
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//// Public License along with this source; if not, download it ////
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//// from http://www.opencores.org/lgpl.shtml ////
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//// ////
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//////////////////////////////////////////////////////////////////////
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//
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// CVS Revision History
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//
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// $Log: eth_clockgen.v,v $
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// Revision 1.4 2005/02/21 12:48:05 igorm
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// Warning fixes.
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//
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// Revision 1.3 2002/01/23 10:28:16 mohor
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// Link in the header changed.
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//
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// Revision 1.2 2001/10/19 08:43:51 mohor
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// eth_timescale.v changed to timescale.v This is done because of the
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// simulation of the few cores in a one joined project.
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//
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// Revision 1.1 2001/08/06 14:44:29 mohor
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// A define FPGA added to select between Artisan RAM (for ASIC) and Block Ram (For Virtex).
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// Include files fixed to contain no path.
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// File names and module names changed ta have a eth_ prologue in the name.
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// File eth_timescale.v is used to define timescale
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// All pin names on the top module are changed to contain _I, _O or _OE at the end.
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// Bidirectional signal MDIO is changed to three signals (Mdc_O, Mdi_I, Mdo_O
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// and Mdo_OE. The bidirectional signal must be created on the top level. This
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// is done due to the ASIC tools.
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//
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// Revision 1.1 2001/07/30 21:23:42 mohor
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// Directory structure changed. Files checked and joind together.
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//
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// Revision 1.3 2001/06/01 22:28:55 mohor
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// This files (MIIM) are fully working. They were thoroughly tested. The testbench is not updated.
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//
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//
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`include "timescale.v"
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module eth_clockgen(Clk, Reset, Divider, MdcEn, MdcEn_n, Mdc);
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parameter Tp=1;
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input Clk; // Input clock (Host clock)
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input Reset; // Reset signal
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input [7:0] Divider; // Divider (input clock will be divided by the Divider[7:0])
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output Mdc; // Output clock
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output MdcEn; // Enable signal is asserted for one Clk period before Mdc rises.
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output MdcEn_n; // Enable signal is asserted for one Clk period before Mdc falls.
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reg Mdc;
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reg [7:0] Counter;
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wire CountEq0;
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wire [7:0] CounterPreset;
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wire [7:0] TempDivider;
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assign TempDivider[7:0] = (Divider[7:0]<2)? 8'h02 : Divider[7:0]; // If smaller than 2
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assign CounterPreset[7:0] = (TempDivider[7:0]>>1) - 1'b1; // We are counting half of period
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// Counter counts half period
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always @ (posedge Clk or posedge Reset)
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begin
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if(Reset)
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Counter[7:0] <= #Tp 8'h1;
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else
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begin
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if(CountEq0)
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begin
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Counter[7:0] <= #Tp CounterPreset[7:0];
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end
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else
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Counter[7:0] <= #Tp Counter - 8'h1;
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end
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end
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// Mdc is asserted every other half period
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always @ (posedge Clk or posedge Reset)
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begin
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if(Reset)
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Mdc <= #Tp 1'b0;
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else
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begin
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if(CountEq0)
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Mdc <= #Tp ~Mdc;
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end
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end
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assign CountEq0 = Counter == 8'h0;
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assign MdcEn = CountEq0 & ~Mdc;
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assign MdcEn_n = CountEq0 & Mdc;
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endmodule
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