| 1 |
30 |
dgisselq |
////////////////////////////////////////////////////////////////////////////////
|
| 2 |
|
|
//
|
| 3 |
|
|
// Filename: addepad.v
|
| 4 |
|
|
//
|
| 5 |
|
|
// Project: OpenArty, an entirely open SoC based upon the Arty platform
|
| 6 |
|
|
//
|
| 7 |
|
|
// Purpose: To force the minimum packet size of an ethernet frame to be
|
| 8 |
|
|
// a minimum of 64 bytes. This assumes that the CRC will be
|
| 9 |
|
|
// adding 32-bits to the packet after us, so instead of padding to
|
| 10 |
|
|
// 64 bytes, we'll pad to 60 bytes instead. If the user is providing
|
| 11 |
|
|
// their own CRC, they'll need to adjust the padding themselves.
|
| 12 |
|
|
//
|
| 13 |
|
|
// Creator: Dan Gisselquist, Ph.D.
|
| 14 |
|
|
// Gisselquist Technology, LLC
|
| 15 |
|
|
//
|
| 16 |
|
|
////////////////////////////////////////////////////////////////////////////////
|
| 17 |
|
|
//
|
| 18 |
|
|
// Copyright (C) 2015-2016, Gisselquist Technology, LLC
|
| 19 |
|
|
//
|
| 20 |
|
|
// This program is free software (firmware): you can redistribute it and/or
|
| 21 |
|
|
// modify it under the terms of the GNU General Public License as published
|
| 22 |
|
|
// by the Free Software Foundation, either version 3 of the License, or (at
|
| 23 |
|
|
// your option) any later version.
|
| 24 |
|
|
//
|
| 25 |
|
|
// This program is distributed in the hope that it will be useful, but WITHOUT
|
| 26 |
|
|
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
|
| 27 |
|
|
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
| 28 |
|
|
// for more details.
|
| 29 |
|
|
//
|
| 30 |
|
|
// You should have received a copy of the GNU General Public License along
|
| 31 |
|
|
// with this program. (It's in the $(ROOT)/doc directory, run make with no
|
| 32 |
|
|
// target there if the PDF file isn't present.) If not, see
|
| 33 |
|
|
// <http://www.gnu.org/licenses/> for a copy.
|
| 34 |
|
|
//
|
| 35 |
|
|
// License: GPL, v3, as defined and found on www.gnu.org,
|
| 36 |
|
|
// http://www.gnu.org/licenses/gpl.html
|
| 37 |
|
|
//
|
| 38 |
|
|
//
|
| 39 |
|
|
////////////////////////////////////////////////////////////////////////////////
|
| 40 |
|
|
//
|
| 41 |
|
|
//
|
| 42 |
|
|
module addepad(i_clk, i_ce, i_en, i_cancel, i_v, i_d, o_v, o_d);
|
| 43 |
|
|
input i_clk, i_ce, i_en, i_cancel;
|
| 44 |
|
|
input i_v; // Valid
|
| 45 |
|
|
input [3:0] i_d; // Data nibble
|
| 46 |
|
|
output reg o_v;
|
| 47 |
|
|
output reg [3:0] o_d;
|
| 48 |
|
|
|
| 49 |
|
|
// 60 bytes translates to 120 nibbles, so let's keep track of our
|
| 50 |
|
|
// minimum number of nibbles to transmit
|
| 51 |
|
|
reg [119:0] r_v;
|
| 52 |
|
|
|
| 53 |
|
|
initial r_v = 120'hff_ffff_ffff_ffff_ffff_ffff_ffff_ffff;
|
| 54 |
|
|
initial o_v = 1'b0;
|
| 55 |
|
|
always @(posedge i_clk)
|
| 56 |
|
|
if (i_ce)
|
| 57 |
|
|
begin
|
| 58 |
|
|
if (((!i_v)&&(!o_v))||(i_cancel))
|
| 59 |
|
|
begin
|
| 60 |
|
|
r_v <= 120'hff_ffff_ffff_ffff_ffff_ffff_ffff_ffff;
|
| 61 |
|
|
o_v <= 1'b0;
|
| 62 |
|
|
end else if (i_v)
|
| 63 |
|
|
begin
|
| 64 |
|
|
o_v <= i_v;
|
| 65 |
|
|
r_v <= { r_v[118:0], 1'b0 };
|
| 66 |
|
|
end else begin
|
| 67 |
|
|
o_v <= r_v[119];
|
| 68 |
|
|
r_v <= { r_v[118:0], 1'b0 };
|
| 69 |
|
|
end
|
| 70 |
|
|
|
| 71 |
|
|
if (i_v)
|
| 72 |
|
|
o_d <= i_d;
|
| 73 |
|
|
else
|
| 74 |
|
|
o_d <= 4'h0;
|
| 75 |
|
|
end
|
| 76 |
|
|
|
| 77 |
|
|
endmodule
|
