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//
// Copyright 2011 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/>.
//
module serdes_fc_rx
#(parameter LWMARK = 64,
parameter HWMARK = 320)
(input clk, input rst,
input [15:0] fifo_space,
output reg send_xon,
output reg send_xoff,
input sent);
reg [15:0] countdown;
reg send_xon_int, send_xoff_int;
always @(posedge clk)
if(rst)
begin
send_xon_int <= 0;
send_xoff_int <= 0;
countdown <= 0;
end
else
begin
send_xon_int <= 0;
send_xoff_int <= 0;
if(countdown == 0)
if(fifo_space < LWMARK)
begin
send_xoff_int <= 1;
countdown <= 240;
end
else
;
else
if(fifo_space > HWMARK)
begin
send_xon_int <= 1;
countdown <= 0;
end
else
countdown <= countdown - 1;
end // else: !if(rst)
// If we are between the high and low water marks, we let the countdown expire
always @(posedge clk)
if(rst)
send_xon <= 0;
else if(send_xon_int)
send_xon <= 1;
else if(sent)
send_xon <= 0;
always @(posedge clk)
if(rst)
send_xoff <= 0;
else if(send_xoff_int)
send_xoff <= 1;
else if(sent)
send_xoff <= 0;
endmodule // serdes_fc_rx
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