Subversion Repositories openrisc_2011-10-31

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////  ORPSoC Testbench UART Decoder                               ////

////                                                              ////

////  Description                                                 ////

////  ORPSoC Testbench UART output decoder                        ////

////                                                              ////

////  To Do:                                                      ////

////                                                              ////

////                                                              ////

////  Author(s):                                                  ////

////      - jb, jb@orsoc.se                                       ////

////                                                              ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

////                                                              ////

//// Copyright (C) 2009 Authors and OPENCORES.ORG                 ////

////                                                              ////

//// This source file may be used and distributed without         ////

//// restriction provided that this copyright statement is not    ////

//// removed from the file and that any derivative work contains  ////

//// the original copyright notice and the associated disclaimer. ////

////                                                              ////

//// This source file is free software; you can redistribute it   ////

//// and/or modify it under the terms of the GNU Lesser General   ////

//// Public License as published by the Free Software Foundation; ////

//// either version 2.1 of the License, or (at your option) any   ////

//// later version.                                               ////

////                                                              ////

//// This source 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 Lesser General Public License for more ////

//// details.                                                     ////

////                                                              ////

//// You should have received a copy of the GNU Lesser General    ////

//// Public License along with this source; if not, download it   ////

//// from http://www.opencores.org/lgpl.shtml                     ////

////                                                              ////

//////////////////////////////////////////////////////////////////////

// Receieves and decodes 8-bit,  1 stop bit, no parity UART signals.

`timescale 1ns/1ns

module uart_decoder(clk, uart_tx);

   input clk;

   input uart_tx;

   // Default baud of 115200, period (ns)

   parameter uart_baudrate_period_ns = 8680;

   // Something to trigger the task

   always @(posedge clk)

     uart_decoder;

   task uart_decoder;

      reg [7:0] tx_byte;

      begin

         while (uart_tx !== 1'b1)

           @(uart_tx);

         // Wait for start bit

         while (uart_tx !== 1'b0)

           @(uart_tx);

         #(uart_baudrate_period_ns+(uart_baudrate_period_ns/2));

         tx_byte[0] = uart_tx;

         #uart_baudrate_period_ns;

         tx_byte[1] = uart_tx;

         #uart_baudrate_period_ns;

         tx_byte[2] = uart_tx;

         #uart_baudrate_period_ns;

         tx_byte[3] = uart_tx;

         #uart_baudrate_period_ns;

         tx_byte[4] = uart_tx;

         #uart_baudrate_period_ns;

         tx_byte[5] = uart_tx;

         #uart_baudrate_period_ns;

         tx_byte[6] = uart_tx;

         #uart_baudrate_period_ns;

         tx_byte[7] = uart_tx;

         #uart_baudrate_period_ns;

         //Check for stop bit

         if (uart_tx !== 1'b1)

           begin

              // Wait for return to idle

              while (uart_tx !== 1'b1)

                @(uart_tx);

           end

         // display the char

         $write("%c", tx_byte);

      end

   endtask // user_uart_read_byte

endmodule // uart_decoder