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                                       ////

////                                                              ////

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//// 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                     ////

////                                                              ////

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

// Decodes UART signals sent over the line defined by UART_TX_LINE

// `include this file in the testbench and define UART_TX_LINE

// Uses define CLOCK_RATE as the frequency of the clock in Hz

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

// Requires definition of:

// CLK_RATE - frequency of system clock in Hz

// CLK_PERIOD - period of clock frequency in ns

// UART_BAUDRATE - otherwise defaults to 115200

// UART_TX_LINE - name of the UART output signal (normally a wire)

// if it's not already defined, uses UART_BAUDRATE as baud to receive

// bytes at

`ifndef UART_BAUDRATE

 `define UART_BAUDRATE 115200

`endif

`ifndef CLOCK_RATE

initial

  begin

     $display("* WARNING: uart_decoder included but CLOCK_RATE not defined.");

  end

`else

 `ifdef UART_TX_LINE

   parameter UART_TX_WAIT = (`CLOCK_RATE / `UART_BAUDRATE) * `CLOCK_PERIOD;

   // Something to trigger the task

   always @(posedge clk)

     uart_decoder;

   task uart_decoder;

      reg [7:0] tx_byte;

      begin

         // Wait for start bit

         while (`UART_TX_LINE == 1'b1)

           @(`UART_TX_LINE);

         #(UART_TX_WAIT+(UART_TX_WAIT/2));

         tx_byte[0] = `UART_TX_LINE;

         #UART_TX_WAIT;

         tx_byte[1] = `UART_TX_LINE;

         #UART_TX_WAIT;

         tx_byte[2] = `UART_TX_LINE;

         #UART_TX_WAIT;

         tx_byte[3] = `UART_TX_LINE;

         #UART_TX_WAIT;

         tx_byte[4] = `UART_TX_LINE;

         #UART_TX_WAIT;

         tx_byte[5] = `UART_TX_LINE;

         #UART_TX_WAIT;

         tx_byte[6] = `UART_TX_LINE;

         #UART_TX_WAIT;

         tx_byte[7] = `UART_TX_LINE;

         #UART_TX_WAIT;

         //Check for stop bit

         if (`UART_TX_LINE == 1'b0)

           begin

              //$display("* WARNING: user stop bit not received when expected at time %d__", $time);

              // Wait for return to idle

              while (`UART_TX_LINE == 1'b0)

                @(`UART_TX_LINE);

              //$display("* USER UART returned to idle at time %d",$time);

           end

         // display the char

         $write("%c", tx_byte);

      end

   endtask // user_uart_read_byte

 `else // !`ifdef UART_TX_LINE

   // If this file was included but not setup properly

   initial

     begin

        $display("* WARNING: uart_decoder included but UART_TX_LINE not defined.");

     end

 `endif // !`ifdef UART_TX_LINE

`endif // !`ifndef CLOCK_RATE