1 //////////////////////////////////////////////////////////////////////
3 //// eth_clockgen.v ////
5 //// This file is part of the Ethernet IP core project ////
6 //// http://www.opencores.org/projects/ethmac/ ////
9 //// - Igor Mohor (igorM@opencores.org) ////
11 //// All additional information is avaliable in the Readme.txt ////
14 //////////////////////////////////////////////////////////////////////
16 //// Copyright (C) 2001 Authors ////
18 //// This source file may be used and distributed without ////
19 //// restriction provided that this copyright statement is not ////
20 //// removed from the file and that any derivative work contains ////
21 //// the original copyright notice and the associated disclaimer. ////
23 //// This source file is free software; you can redistribute it ////
24 //// and/or modify it under the terms of the GNU Lesser General ////
25 //// Public License as published by the Free Software Foundation; ////
26 //// either version 2.1 of the License, or (at your option) any ////
27 //// later version. ////
29 //// This source is distributed in the hope that it will be ////
30 //// useful, but WITHOUT ANY WARRANTY; without even the implied ////
31 //// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR ////
32 //// PURPOSE. See the GNU Lesser General Public License for more ////
35 //// You should have received a copy of the GNU Lesser General ////
36 //// Public License along with this source; if not, download it ////
37 //// from http://www.opencores.org/lgpl.shtml ////
39 //////////////////////////////////////////////////////////////////////
41 // CVS Revision History
43 // $Log: eth_clockgen.v,v $
44 // Revision 1.2 2005/12/13 12:54:49 maverickist
45 // first simulation passed
47 // Revision 1.1.1.1 2005/12/13 01:51:45 Administrator
50 // Revision 1.2 2005/04/27 15:58:45 Administrator
53 // Revision 1.1.1.1 2004/12/15 06:38:54 Administrator
56 // Revision 1.3 2002/01/23 10:28:16 mohor
57 // Link in the header changed.
59 // Revision 1.2 2001/10/19 08:43:51 mohor
60 // eth_timescale.v changed to timescale.v This is done because of the
61 // simulation of the few cores in a one joined project.
63 // Revision 1.1 2001/08/06 14:44:29 mohor
64 // A define FPGA added to select between Artisan RAM (for ASIC) and Block Ram (For Virtex).
65 // Include files fixed to contain no path.
66 // File names and module names changed ta have a eth_ prologue in the name.
67 // File eth_timescale.v is used to define timescale
68 // All pin names on the top module are changed to contain _I, _O or _OE at the end.
69 // Bidirectional signal MDIO is changed to three signals (Mdc_O, Mdi_I, Mdo_O
70 // and Mdo_OE. The bidirectional signal must be created on the top level. This
71 // is done due to the ASIC tools.
73 // Revision 1.1 2001/07/30 21:23:42 mohor
74 // Directory structure changed. Files checked and joind together.
76 // Revision 1.3 2001/06/01 22:28:55 mohor
77 // This files (MIIM) are fully working. They were thoroughly tested. The testbench is not updated.
81 module eth_clockgen(Clk, Reset, Divider, MdcEn, MdcEn_n, Mdc);
85 input Clk; // Input clock (Host clock)
86 input Reset; // Reset signal
87 input [7:0] Divider; // Divider (input clock will be divided by the Divider[7:0])
89 output Mdc; // Output clock
90 output MdcEn; // Enable signal is asserted for one Clk period before Mdc rises.
91 output MdcEn_n; // Enable signal is asserted for one Clk period before Mdc falls.
97 wire [7:0] CounterPreset;
98 wire [7:0] TempDivider;
101 assign TempDivider[7:0] = (Divider[7:0]<2)? 8'h02 : Divider[7:0]; // If smaller than 2
102 assign CounterPreset[7:0] = (TempDivider[7:0]>>1) -1; // We are counting half of period
105 // Counter counts half period
106 always @ (posedge Clk or posedge Reset)
109 Counter[7:0] <= #Tp 8'h1;
114 Counter[7:0] <= #Tp CounterPreset[7:0];
117 Counter[7:0] <= #Tp Counter - 8'h1;
122 // Mdc is asserted every other half period
123 always @ (posedge Clk or posedge Reset)
135 assign CountEq0 = Counter == 8'h0;
136 assign MdcEn = CountEq0 & ~Mdc;
137 assign MdcEn_n = CountEq0 & Mdc;
139 endmodule // eth_clockgen