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// -*- verilog -*-
//
// USRP - Universal Software Radio Peripheral
//
// Copyright (C) 2007 Corgan Enterprises 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 2 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, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Boston, MA 02110-1301 USA
//
module atr_delay(clk_i,rst_i,ena_i,tx_empty_i,tx_delay_i,rx_delay_i,atr_tx_o);
input clk_i;
input rst_i;
input ena_i;
input tx_empty_i;
input [11:0] tx_delay_i;
input [11:0] rx_delay_i;
output atr_tx_o;
reg [3:0] state;
reg [11:0] count;
`define ST_RX_DELAY 4'b0001
`define ST_RX 4'b0010
`define ST_TX_DELAY 4'b0100
`define ST_TX 4'b1000
always @(posedge clk_i)
if (rst_i | ~ena_i)
begin
state <= `ST_RX;
count <= 12'b0;
end
else
case (state)
`ST_RX:
if (!tx_empty_i)
begin
state <= `ST_TX_DELAY;
count <= tx_delay_i;
end
`ST_TX_DELAY:
if (count == 0)
state <= `ST_TX;
else
count <= count - 1;
`ST_TX:
if (tx_empty_i)
begin
state <= `ST_RX_DELAY;
count <= rx_delay_i;
end
`ST_RX_DELAY:
if (count == 0)
state <= `ST_RX;
else
count <= count - 1;
default: // Error
begin
state <= `ST_RX;
count <= 0;
end
endcase
assign atr_tx_o = (state == `ST_TX) | (state == `ST_RX_DELAY);
endmodule // atr_delay
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