////////////////////////////////////////////////////////////////////// //// //// //// eth_clockgen.v //// //// //// //// This file is part of the Ethernet IP core project //// //// http://www.opencores.org/cores/ethmac/ //// //// //// //// Author(s): //// //// - Igor Mohor (igorM@opencores.org) //// //// //// //// All additional information is avaliable in the Readme.txt //// //// file. //// //// //// ////////////////////////////////////////////////////////////////////// //// //// //// Copyright (C) 2001 Authors //// //// //// //// 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 source file is free software; you can redistribute it //// //// and/or modify it under the terms of the GNU Lesser General //// //// Public License as published by the Free Software Foundation; //// //// either version 2.1 of the License, or (at your option) any //// //// later version. //// //// //// //// This source is distributed in the hope that it will be //// //// useful, but WITHOUT ANY WARRANTY; without even the implied //// //// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR //// //// PURPOSE. See the GNU Lesser General Public License for more //// //// details. //// //// //// //// You should have received a copy of the GNU Lesser General //// //// Public License along with this source; if not, download it //// //// from http://www.opencores.org/lgpl.shtml //// //// //// ////////////////////////////////////////////////////////////////////// // // CVS Revision History // // $Log: not supported by cvs2svn $ // Revision 1.1 2001/07/30 21:23:42 mohor // Directory structure changed. Files checked and joind together. // // Revision 1.3 2001/06/01 22:28:55 mohor // This files (MIIM) are fully working. They were thoroughly tested. The testbench is not updated. // // `include "eth_timescale.v" module eth_clockgen(Clk, Reset, Divider, MdcEn, MdcEn_n, Mdc); parameter Tp=1; input Clk; // Input clock (Host clock) input Reset; // Reset signal input [7:0] Divider; // Divider (input clock will be divided by the Divider[7:0]) output Mdc; // Output clock output MdcEn; // Enable signal is asserted for one Clk period before Mdc rises. output MdcEn_n; // Enable signal is asserted for one Clk period before Mdc falls. reg Mdc; reg [7:0] Counter; wire CountEq0; wire [7:0] CounterPreset; wire [7:0] TempDivider; assign TempDivider[7:0] = (Divider[7:0]<2)? 8'h02 : Divider[7:0]; // If smaller than 2 assign CounterPreset[7:0] = (TempDivider[7:0]>>1) -1; // We are counting half of period // Counter counts half period always @ (posedge Clk or posedge Reset) begin if(Reset) Counter[7:0] <= #Tp 8'h1; else begin if(CountEq0) begin Counter[7:0] <= #Tp CounterPreset[7:0]; end else Counter[7:0] <= #Tp Counter - 8'h1; end end // Mdc is asserted every other half period always @ (posedge Clk or posedge Reset) begin if(Reset) Mdc <= #Tp 1'b0; else begin if(CountEq0) Mdc <= #Tp ~Mdc; end end assign CountEq0 = Counter == 8'h0; assign MdcEn = CountEq0 & ~Mdc; assign MdcEn_n = CountEq0 & Mdc; endmodule