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//
// Copyright 2012 Ettus Research LLC
//
// This program is free software: 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
// MERCHANTABILITY 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. If not, see <http://www.gnu.org/licenses/>.
//
// Hold packets in fifo until they are complete. This prevents slowly-built packets
// from clogging up the downstream. This block will hold up to 255 packets.
// Will permanently block if a single packet is bigger than the fifo.
// Will also drop any packet with an error signalled on the last line.
// This is useful after an ethernet interface to drop packets with bad CRCs.
module axi_packet_gate
#(parameter WIDTH=68,
parameter SIZE=10)
(input clk,
input reset,
input clear,
input [WIDTH-1:0] i_tdata,
input i_tlast,
input i_terror,
input i_tvalid,
output i_tready,
output [WIDTH-1:0] o_tdata,
output o_tlast,
output o_tvalid,
input o_tready
);
reg [7:0] num_packets;
reg dump;
wire o_tvalid_int, o_tready_int, i_tvalid_int, i_tready_int;
assign i_tvalid_int = (~dump & (num_packets != 8'hFF)) ? i_tvalid : 1'b0;
assign i_tready = (~dump & (num_packets != 8'hFF)) ? i_tready_int : 1'b0;
assign o_tvalid = (num_packets != 8'h0) ? o_tvalid_int : 1'b0;
assign o_tready_int = (num_packets != 8'h0) ? o_tready : 1'b0;
wire last_in = i_tvalid_int & i_tready_int & i_tlast;
wire last_out = o_tvalid_int & o_tready_int & o_tlast;
always @(posedge clk)
if(reset | clear)
begin
num_packets <= 8'd0;
dump <= 1'b0;
end
else
if(dump)
if(num_packets != 8'd0)
if(last_out)
num_packets <= num_packets - 8'd1;
else
;
else
dump <= 1'b0;
else
if(last_in)
if(i_terror)
begin
dump <= 1'b1;
if(last_out)
num_packets <= num_packets - 8'd1;
end
else if(~last_out)
num_packets <= num_packets + 8'd1;
else
;
else if(last_out)
num_packets <= num_packets - 8'd1;
axi_fifo #(.SIZE(SIZE), .WIDTH(WIDTH+1)) axi_fifo
(.clk(clk), .reset(reset), .clear(clear | (dump & (num_packets == 8'd0))),
.i_tdata({i_tlast,i_tdata}), .i_tvalid(i_tvalid_int), .i_tready(i_tready_int),
.o_tdata({o_tlast,o_tdata}), .o_tvalid(o_tvalid_int), .o_tready(o_tready_int));
endmodule // axi_packet_gate
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