Subversion Repositories openrisc_2011-10-31

// ----------------------------------------------------------------------------

// SystemC Uart: implementation

// This file is part of the cycle accurate model of the OpenRISC 1000 based

// system-on-chip, ORPSoC, built using Verilator.

// This program 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 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 Lesser General Public

// License for more details.

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

// along with this program.  If not, see <http://www.gnu.org/licenses/>.

// ----------------------------------------------------------------------------

// $Id: $

#include <iostream>

#include <iomanip>

#include <cmath>

#include "UartSC.h"

//#define UART_SC_DEBUG

SC_HAS_PROCESS( UartSC );

//! Constructor for the Uart system C model

//! @param[in] name  Name of this module, passed to the parent constructor.

// Todo: Probably some sort of scaler parameter

UartSC::UartSC (sc_core::sc_module_name   name):

  sc_module (name)

{

  SC_METHOD (checkTx);

  dont_initialize();

  sensitive << clk.pos();

  //sensitive << uarttx;

}       // UartSC ()

void

UartSC::initUart (int clk_freq_hz, // Presume in NS

                  int uart_baud

                  )

{

  // Calculate number of clocks per UART bit

  clocks_per_bit = (int)(clk_freq_hz/uart_baud);

  bits_received=0;

#ifdef UART_SC_DEBUG

  printf("UartSC Initialised: Sys. clk. freq.: %d Hz, Baud: %d, cpb: %d\n", clk_freq_hz, uart_baud, clocks_per_bit);

#endif

}

// Maybe do this with threads instead?!

void

UartSC::checkTx () {

#ifdef UART_SC_DEBUG

  //printf("Uart TX activity: level is : 0x%x\n", uarttx.read()&1);

#endif

  // Check the number of bits received

  if (bits_received==0)

    {

      // Check if tx is low

      if ((uarttx.read()&1) == 0)

        {

          // Line pulled low, begin receive of new char

          current_char = 0;

          // Start 

          counter = 1;

          bits_received++; // We got the start bit

#ifdef UART_SC_DEBUG

          cout << "UartSC checkTx: got start bit at time " << sc_time_stamp() << endl;

#endif

        }

    }

  else if (bits_received > 0 && bits_received < 9)

    {

      // Check the counter - see if it's time to sample the line

      // We do an extra half-bit delay on first bit read

      if ( ((bits_received==1) &&

            (counter == (clocks_per_bit + (clocks_per_bit/2)))) ||

           ((bits_received > 1) && (counter == clocks_per_bit)) )

        {

          //printf("UartSC checkTx: read bit %d as 0x%x at time", bits_received, uarttx.read()&1);

          //cout << sc_time_stamp() << endl;

          // Shift in the current value of the tx into our char

          current_char |= ((uarttx.read() & 1) << (bits_received-1));

          // Reset the counter

          counter = 1;

          // Increment bit number

          bits_received++;

        }

      else

        counter++;

    }

  else if (bits_received == 9)

    {

      // Now check for stop bit 1

      if (counter == clocks_per_bit)

        {

          // Check that the value is 1 - this should be the stop bit

          if ((uarttx.read() & 1) != 1)

            {

              printf("UART TX framing error at time\n");

              cout << sc_time_stamp() << endl;

              // Perhaps do something else here to deal with this

              bits_received = 0;

              counter = 0;

            }

          else

            {

              // Print the char

#ifdef UART_SC_DEBUG

              printf("Char received: 0x%2x time: ", current_char);

              cout << sc_time_stamp() << endl;

#endif

              // cout'ing the char didn't work for some systems - jb 090613ol

              //cout << current_char;

              printf("%c",current_char);

              bits_received = 0;

              counter = 0;

            }

        }

      else

        counter++;

    }

}