Bochs/bochs/iodev/floppy.cc

  ///////////////////////////////////////////////////////////////////////////
// $Id: floppy.cc,v 1.39 2002-06-16 15:02:27 vruppert Exp $
/////////////////////////////////////////////////////////////////////////
//
//  Copyright (C) 2002  MandrakeSoft S.A.
//
//    MandrakeSoft S.A.
//    43, rue d'Aboukir
//    75002 Paris - France
//    http://www.linux-mandrake.com/
//    http://www.mandrakesoft.com/
//
//  This library 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 of the License, or (at your option) any later version.
//
//  This library 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 library; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
//
//
// Floppy Disk Controller Docs:
// Intel 82077A Data sheet
//   ftp://void-core.2y.net/pub/docs/fdc/82077AA_FloppyControllerDatasheet.pdf
// Intel 82078 Data sheet
//   ftp://download.intel.com/design/periphrl/datashts/29047403.PDF
// Other FDC references
//   http://debs.future.easyspace.com/Programming/Hardware/FDC/floppy.html
// And a port list:
//   http://mudlist.eorbit.net/~adam/pickey/ports.html
//

extern "C" {
#include <errno.h>
}
#include "bochs.h"
#ifdef WIN32
#include <windows.h>     // for wsprintf
#endif
#define LOG_THIS bx_floppy.


bx_floppy_ctrl_c bx_floppy;

#if BX_USE_FD_SMF
#define this (&bx_floppy)
#endif



/* for main status register */
#define FD_MS_MRQ  0x80
#define FD_MS_DIO  0x40
#define FD_MS_NDMA 0x20
#define FD_MS_BUSY 0x10
#define FD_MS_ACTD 0x08
#define FD_MS_ACTC 0x04
#define FD_MS_ACTB 0x02
#define FD_MS_ACTA 0x01

#define FROM_FLOPPY 10
#define TO_FLOPPY   11

#define FLOPPY_DMA_CHAN 2



bx_floppy_ctrl_c::bx_floppy_ctrl_c(void)
{
	put("FDD");
	settype(FDLOG);
}

bx_floppy_ctrl_c::~bx_floppy_ctrl_c(void)
{
	// nothing for now
	BX_DEBUG(("Exit."));
}


  void
bx_floppy_ctrl_c::init(bx_devices_c *d, bx_cmos_c *cmos)
{
	BX_DEBUG(("Init $Id: floppy.cc,v 1.39 2002-06-16 15:02:27 vruppert Exp $"));
  BX_FD_THIS devices = d;

  BX_REGISTER_DMA8_CHANNEL(2, bx_floppy.dma_read, bx_floppy.dma_write, "Floppy Drive");
  BX_FD_THIS devices->register_irq(6, "Floppy Drive");
  for (unsigned addr=0x03F2; addr<=0x03F7; addr++) {
    BX_FD_THIS devices->register_io_read_handler(this, read_handler,
                                      addr, "Floppy Drive");
    BX_FD_THIS devices->register_io_write_handler(this, write_handler,
                                      addr, "Floppy Drive");
    }


  cmos->s.reg[0x10] = 0x00; /* start out with: no drive 0, no drive 1 */

  BX_FD_THIS s.num_supported_floppies = 0;

  //
  // Floppy A setup
  //
  BX_FD_THIS s.media[0].sectors_per_track = 0;
  BX_FD_THIS s.media[0].tracks            = 0;
  BX_FD_THIS s.media[0].heads             = 0;
  BX_FD_THIS s.media[0].sectors           = 0;
  BX_FD_THIS s.media[0].type              = BX_FLOPPY_NONE;
  BX_FD_THIS s.media[0].fd = -1;
  BX_FD_THIS s.media_present[0] = 0;


  switch (bx_options.floppya.Otype->get ()) {
    case BX_FLOPPY_NONE:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0x0f) | 0x00;
      break;
    case BX_FLOPPY_1_2:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0x0f) | 0x20;
      break;
    case BX_FLOPPY_720K:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0x0f) | 0x30;
      break;
    case BX_FLOPPY_1_44:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0x0f) | 0x40;
      break;
    case BX_FLOPPY_2_88:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0x0f) | 0x50;
      break;
    default:
      BX_PANIC(("unknown floppya type"));
    }

  if (bx_options.floppya.Otype->get () != BX_FLOPPY_NONE) {
    BX_FD_THIS s.num_supported_floppies++;
    if ( bx_options.floppya.Oinitial_status->get () == BX_INSERTED) {
      if (evaluate_media(bx_options.floppya.Otype->get (), bx_options.floppya.Opath->getptr (),
                   & BX_FD_THIS s.media[0]))
        BX_FD_THIS s.media_present[0] = 1;
#define MED (BX_FD_THIS s.media[0])
    	BX_INFO(("fd0: '%s' ro=%d, h=%d,t=%d,spt=%d", bx_options.floppya.Opath->getptr(),
			MED.write_protected, MED.heads, MED.tracks, MED.sectors_per_track));
#undef MED
      }
    }


  //
  // Floppy B setup
  //
  BX_FD_THIS s.media[1].sectors_per_track = 0;
  BX_FD_THIS s.media[1].tracks            = 0;
  BX_FD_THIS s.media[1].heads             = 0;
  BX_FD_THIS s.media[1].sectors           = 0;
  BX_FD_THIS s.media[1].type              = BX_FLOPPY_NONE;
  BX_FD_THIS s.media[1].fd = -1;
  BX_FD_THIS s.media_present[1] = 0;

  switch (bx_options.floppyb.Otype->get ()) {
    case BX_FLOPPY_NONE:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0xf0) | 0x00;
      break;
    case BX_FLOPPY_1_2:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0xf0) | 0x02;
      break;
    case BX_FLOPPY_720K:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0xf0) | 0x03;
      break;
    case BX_FLOPPY_1_44:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0xf0) | 0x04;
      break;
    case BX_FLOPPY_2_88:
      cmos->s.reg[0x10] = (cmos->s.reg[0x10] & 0xf0) | 0x05;
      break;
    default:
      BX_PANIC(("unknown floppyb type"));
    }

  if (bx_options.floppyb.Otype->get () != BX_FLOPPY_NONE) {
    BX_FD_THIS s.num_supported_floppies++;
    if ( bx_options.floppyb.Oinitial_status->get () == BX_INSERTED) {
      if (evaluate_media(bx_options.floppyb.Otype->get (), bx_options.floppyb.Opath->getptr (),
                   & BX_FD_THIS s.media[1]))
        BX_FD_THIS s.media_present[1] = 1;
#define MED (BX_FD_THIS s.media[1])
    	BX_INFO(("fd1: '%s' ro=%d, h=%d,t=%d,spt=%d", bx_options.floppyb.Opath->getptr(),
			MED.write_protected, MED.heads, MED.tracks, MED.sectors_per_track));
#undef MED
      }
    }



  /* CMOS Equipment Byte register */
  if (BX_FD_THIS s.num_supported_floppies > 0)
    cmos->s.reg[0x14] = (cmos->s.reg[0x14] & 0x3e) |
                        ((BX_FD_THIS s.num_supported_floppies-1) << 6) |
                        1;
  else
    cmos->s.reg[0x14] = (cmos->s.reg[0x14] & 0x3e);


  BX_FD_THIS s.floppy_timer_index =
    bx_pc_system.register_timer( this, timer_handler,
      bx_options.Ofloppy_command_delay->get (), 0,0);

  BX_DEBUG(("bx_options.Ofloppy_command_delay = %u",
    (unsigned) bx_options.Ofloppy_command_delay->get ()));
}



  void
bx_floppy_ctrl_c::reset(unsigned source)
{
  Bit32u i;

  BX_FD_THIS s.command_complete = 1; /* waiting for new command */
  BX_FD_THIS s.command_index = 0;
  BX_FD_THIS s.command_size = 0;
  BX_FD_THIS s.pending_command = 0;

  BX_FD_THIS s.pending_irq = 0;
  BX_FD_THIS s.reset_sensei = 0; /* no reset result present */

  BX_FD_THIS s.result_index = 0;
  BX_FD_THIS s.result_size = 0;

  /* data register ready, not in DMA mode */
  BX_FD_THIS s.main_status_reg = FD_MS_MRQ;
  BX_FD_THIS s.status_reg0 = 0;
  BX_FD_THIS s.status_reg1 = 0;
  BX_FD_THIS s.status_reg2 = 0;
  BX_FD_THIS s.status_reg3 = 0;

  // software reset (via DOR port 0x3f2 bit 2) does not change DOR
  if (source == BX_RESET_HARDWARE) {
    BX_FD_THIS s.DOR = 0x0c;
    // motor off, drive 3..0
    // DMA/INT enabled
    // normal operation
    // drive select 0

    // DIR and CCR affected only by hard reset
    BX_FD_THIS s.DIR |= 0x80; // disk changed
    BX_FD_THIS s.data_rate = 0; /* 500 Kbps */
    }

  for (i=0; i<4; i++) {
    BX_FD_THIS s.cylinder[i] = 0;
    BX_FD_THIS s.head[i] = 0;
    BX_FD_THIS s.sector[i] = 0;
    }

  BX_FD_THIS s.floppy_buffer_index = 0;

  BX_FD_THIS devices->pic->lower_irq(6);
  BX_DMA_SET_DRQ(FLOPPY_DMA_CHAN, 0);
}


  // static IO port read callback handler
  // redirects to non-static class handler to avoid virtual functions

  Bit32u
bx_floppy_ctrl_c::read_handler(void *this_ptr, Bit32u address, unsigned io_len)
{
#if !BX_USE_FD_SMF
  bx_floppy_ctrl_c *class_ptr = (bx_floppy_ctrl_c *) this_ptr;

  return( class_ptr->read(address, io_len) );
}


  /* reads from the floppy io ports */
  Bit32u
bx_floppy_ctrl_c::read(Bit32u address, unsigned io_len)
{
#else
  UNUSED(this_ptr);
#endif  // !BX_USE_FD_SMF
  Bit8u status, value;

  if (io_len > 1)
    BX_PANIC(("io read from address %08x, len=%u",
             (unsigned) address, (unsigned) io_len));

  if (bx_dbg.floppy)
    BX_INFO(("read access to port %04x", (unsigned) address));

  switch (address) {
#if BX_DMA_FLOPPY_IO
    case 0x3F2: // diskette controller digital output register
      value = BX_FD_THIS s.DOR;
      return(value);
      break;

    case 0x3F4: /* diskette controller main status register */
      status = BX_FD_THIS s.main_status_reg;
      return(status);
      break;

    case 0x3F5: /* diskette controller data */
      if (BX_FD_THIS s.result_size == 0) {
        BX_ERROR(("port 0x3f5: no results to read"));
        BX_FD_THIS s.main_status_reg = 0;
        return BX_FD_THIS s.result[0];
        }

      value = BX_FD_THIS s.result[BX_FD_THIS s.result_index++];
      BX_FD_THIS s.main_status_reg &= 0xF0;
      if (BX_FD_THIS s.result_index >= BX_FD_THIS s.result_size) {
        BX_FD_THIS s.result_size = 0;
        BX_FD_THIS s.result_index = 0;
        BX_FD_THIS s.result[0] = value;
        BX_FD_THIS s.main_status_reg = FD_MS_MRQ;
        if (!BX_FD_THIS s.reset_sensei) BX_FD_THIS s.pending_irq = 0;
        BX_FD_THIS devices->pic->lower_irq(6);
        }
      return(value);
      break;
#endif  // #if BX_DMA_FLOPPY_IO

    case 0x3F3: // Tape Drive Register
      // see http://www.smsc.com/main/datasheets/37c93x.pdf page 18 for more details

      switch( BX_FD_THIS s.DOR & 0x03 )
      {
	case 0x00:
	  if( (BX_FD_THIS s.DOR & 0x10) == 0) break;
	  return(2);
	case 0x01:
	  if( (BX_FD_THIS s.DOR & 0x20) == 0) break;
	  return(1);
      }
      return(3);
      
    case 0x3F6: // Reserved for future floppy controllers
                // This address shared with the hard drive controller
      value = BX_FD_THIS devices->hard_drive->read_handler(BX_FD_THIS devices->hard_drive, address, io_len);
      return( value );
      break;

    case 0x3F7: // diskette controller digital input register
      // This address shared with the hard drive controller:
      //   Bit  7   : floppy
      //   Bits 6..0: hard drive
      value = BX_FD_THIS devices->hard_drive->read_handler(BX_FD_THIS devices->hard_drive, address, io_len);
      value &= 0x7f;
      // add in diskette change line
      value |= (BX_FD_THIS s.DIR & 0x80);
      return( value );
      break;
    default:
      BX_ERROR(("io_read: unsupported address 0x%04x", (unsigned) address));
      return(0);
      break;
    }
}


  // static IO port write callback handler
  // redirects to non-static class handler to avoid virtual functions

  void
bx_floppy_ctrl_c::write_handler(void *this_ptr, Bit32u address, Bit32u value, unsigned io_len)
{
#if !BX_USE_FD_SMF
  bx_floppy_ctrl_c *class_ptr = (bx_floppy_ctrl_c *) this_ptr;

  class_ptr->write(address, value, io_len);
}

  /* writes to the floppy io ports */
  void
bx_floppy_ctrl_c::write(Bit32u address, Bit32u value, unsigned io_len)
{
#else
  UNUSED(this_ptr);
#endif  // !BX_USE_FD_SMF
  Bit8u dma_and_interrupt_enable;
  Bit8u normal_operation, prev_normal_operation;
  Bit8u drive_select;
  Bit8u motor_on_drive0, motor_on_drive1;

  if (io_len > 1)
    BX_PANIC(("io write to address %08x, len=%u",
             (unsigned) address, (unsigned) io_len));

  if (bx_dbg.floppy)
    BX_INFO(("write access to port %04x, value=%02x",
      (unsigned) address, (unsigned) value));

  switch (address) {
#if BX_DMA_FLOPPY_IO
    case 0x3F2: /* diskette controller digital output register */
      motor_on_drive1 = value & 0x20;
      motor_on_drive0 = value & 0x10;
      dma_and_interrupt_enable = value & 0x08;
      if (!dma_and_interrupt_enable)
        BX_DEBUG(("DMA and interrupt capabilities disabled"));
      normal_operation = value & 0x04;
      drive_select = value & 0x03;

      prev_normal_operation = BX_FD_THIS s.DOR & 0x04;
      BX_FD_THIS s.DOR = value;

      if (prev_normal_operation==0 && normal_operation) {
        // transition from RESET to NORMAL
        bx_pc_system.activate_timer( BX_FD_THIS s.floppy_timer_index,
             bx_options.Ofloppy_command_delay->get (), 0 );
        }
      else if (prev_normal_operation && normal_operation==0) {
        // transition from NORMAL to RESET
        BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
        BX_FD_THIS s.pending_command = 0xfe; // RESET pending

        }
        BX_DEBUG(("io_write: digital output register"));
        BX_DEBUG(("  motor on, drive1 = %d", motor_on_drive1 > 0));
        BX_DEBUG(("  motor on, drive0 = %d", motor_on_drive0 > 0));
        BX_DEBUG(("  dma_and_interrupt_enable=%02x",
          (unsigned) dma_and_interrupt_enable));
        BX_DEBUG(("  normal_operation=%02x",
          (unsigned) normal_operation));
        BX_DEBUG(("  drive_select=%02x",
          (unsigned) drive_select));
      if (drive_select>1) {
	BX_DEBUG(("WARNING: applying mod(2) on drive_select"));
	drive_select &= 0x01;
	BX_DEBUG(("new drive_select=%d", (unsigned) drive_select));
        }
      break;

    case 0x3f4: /* diskette controller data rate select register */
      BX_ERROR(("io_write: data rate select register unsupported"));
      break;

    case 0x3F5: /* diskette controller data */
      BX_DEBUG(("command = %02x", (unsigned) value));
      if (BX_FD_THIS s.command_complete) {
        if (BX_FD_THIS s.pending_command!=0)
          BX_PANIC(("io: 3f5: receiving new comm, old one (%02x) pending",
            (unsigned) BX_FD_THIS s.pending_command));
        BX_FD_THIS s.command[0] = value;
        BX_FD_THIS s.command_complete = 0;
        BX_FD_THIS s.command_index = 1;
        /* read/write command in progress */
        BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_BUSY;
        switch (value) {
          case 0x03: /* specify */
            BX_FD_THIS s.command_size = 3;
            break;
          case 0x04: // get status
            BX_FD_THIS s.command_size = 2;
            break;
          case 0x07: /* recalibrate */
            BX_FD_THIS s.command_size = 2;
            break;
          case 0x08: /* sense interrupt status */
            BX_FD_THIS s.command_size = 1;
            break;
          case 0x0f: /* seek */
            BX_FD_THIS s.command_size = 3;
            break;
          case 0x4a: /* read ID */
            BX_FD_THIS s.command_size = 2;
            break;
          case 0x4d: /* format track */
            BX_FD_THIS s.command_size = 6;
            break;
          case 0x45:
          case 0xc5: /* write normal data */
            BX_FD_THIS s.command_size = 9;
            break;
          case 0x66:
          case 0xe6: /* read normal data */
            BX_FD_THIS s.command_size = 9;
            break;

          case 0x13: // Configure command (Enhanced)
            BX_FD_THIS s.command_size = 4;
            break;

          case 0x0e: // dump registers (Enhanced drives)
          case 0x10: // Version command, standard controller returns 80h
          case 0x18: // National Semiconductor version command; return 80h
            // These commands are not implemented on the standard
            // controller and return an error.  They are available on
            // the enhanced controller.
            BX_DEBUG(("io_write: 0x3f5: unsupported floppy command 0x%02x",
              (unsigned) value));
            BX_FD_THIS s.command_size = 1;
            BX_FD_THIS s.status_reg0 = 0x80; // status: invalid command
            break;

          default:
            BX_ERROR(("io_write: 0x3f5: invalid floppy command 0x%02x",
              (unsigned) value));
            BX_FD_THIS s.command_size = 1;
            BX_FD_THIS s.status_reg0 = 0x80; // status: invalid command
            break;
          }
        }
      else {
        BX_FD_THIS s.command[BX_FD_THIS s.command_index++] =
          value;
        }
      if (BX_FD_THIS s.command_index ==
        BX_FD_THIS s.command_size) {
        /* read/write command not in progress any more */
        floppy_command();
        BX_FD_THIS s.command_complete = 1;
        }
      BX_DEBUG(("io_write: diskette controller data"));
      return;
      break;
#endif  // #if BX_DMA_FLOPPY_IO

    case 0x3F6: /* diskette controller (reserved) */
      BX_DEBUG(("io_write: reserved register unsupported"));
      // this address shared with the hard drive controller
      BX_FD_THIS devices->hard_drive->write_handler(BX_FD_THIS devices->hard_drive, address, value, io_len);
      break;

#if BX_DMA_FLOPPY_IO
    case 0x3F7: /* diskette controller configuration control register */
      BX_DEBUG(("io_write: config control register"));
      BX_FD_THIS s.data_rate = value & 0x03;
      switch (BX_FD_THIS s.data_rate) {
        case 0: BX_DEBUG(("  500 Kbps")); break;
        case 1: BX_DEBUG(("  300 Kbps")); break;
        case 2: BX_DEBUG(("  250 Kbps")); break;
        case 3: BX_DEBUG(("  1 Mbps")); break;
      }
      return;
      break;

   default:
      BX_ERROR(("io_write ignored: 0x%04h = 0x%02h", (unsigned) address, (unsigned) value));
      break;
#endif  // #if BX_DMA_FLOPPY_IO
    }
}



  void
bx_floppy_ctrl_c::floppy_command(void)
{
#if BX_PROVIDE_CPU_MEMORY==0
  BX_PANIC(("floppy_command(): uses DMA: not supported for"
           " external environment"));
#else
  unsigned i;
  Bit8u step_rate_time;
  Bit8u head_unload_time;
  Bit8u head_load_time;
  Bit8u motor_on;
  Bit8u head, drive, cylinder, sector, eot;
  Bit8u sector_size, data_length;
  Bit32u logical_sector;


  BX_DEBUG(("FLOPPY COMMAND: "));
  for (i=0; i<BX_FD_THIS s.command_size; i++)
    BX_DEBUG(("[%02x] ", (unsigned) BX_FD_THIS s.command[i]));

#if 0
  /* execute phase of command is in progress (non DMA mode) */
  BX_FD_THIS s.main_status_reg |= 20;
#endif

  switch (BX_FD_THIS s.command[0]) {
    case 0x03: // specify
      // execution: specified parameters are loaded
      // result: no result bytes, no interrupt
      step_rate_time = BX_FD_THIS s.command[1] >> 4;
      head_unload_time = BX_FD_THIS s.command[1] & 0x0f;
      head_load_time = BX_FD_THIS s.command[2] >> 1;
      if (BX_FD_THIS s.command[2] & 0x01)
        BX_ERROR(("non DMA mode selected"));
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ;
      return;
      break;

    case 0x04: // get status
      drive = (BX_FD_THIS s.command[1] & 0x03);
      BX_FD_THIS s.result[0] = 0x28 | (BX_FD_THIS s.head[drive]<<2) | drive
        | (BX_FD_THIS s.media[drive].write_protected ? 0x40 : 0x00);
      if (BX_FD_THIS s.cylinder[drive] == 0) BX_FD_THIS s.result[0] |= 0x10;
      BX_FD_THIS s.result_size = 1;
      BX_FD_THIS s.result_index = 0;
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY;
      return;
      break;

    case 0x07: // recalibrate
      drive = (BX_FD_THIS s.command[1] & 0x03);
      BX_FD_THIS s.DOR &= 0xfc;
      BX_FD_THIS s.DOR |= drive;
      BX_DEBUG(("floppy_command(): recalibrate drive %u",
        (unsigned) drive));
      if (drive > 1)
        BX_PANIC(("floppy_command(): drive > 1"));
      //motor_on = BX_FD_THIS s.DOR & 0xf0;
      motor_on = ( (BX_FD_THIS s.DOR>>(drive+4))
                     & 0x01 );
      if (motor_on == 0) {
        BX_INFO(("floppy_command(): recal drive with motor off"));
        }
      if (drive==0)
        BX_FD_THIS s.DOR |= 0x10; // turn on MOTA
      else
        BX_FD_THIS s.DOR |= 0x20; // turn on MOTB
      BX_FD_THIS s.cylinder[drive] = 0;
      bx_pc_system.activate_timer( BX_FD_THIS s.floppy_timer_index,
        bx_options.Ofloppy_command_delay->get (), 0 );
      /* command head to track 0
       * controller set to non-busy
       * error condition noted in Status reg 0's equipment check bit
       * seek end bit set to 1 in Status reg 0 regardless of outcome
       */
      /* data reg not ready, controller busy */
      BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
      BX_FD_THIS s.pending_command = 0x07; // recalibrate pending
      return;
      break;

    case 0x08: /* sense interrupt status */
      /* execution:
       *   get status
       * result:
       *   no interupt
       *   byte0 = status reg0
       *   byte1 = current cylinder number (0 to 79)
       */
      drive = BX_FD_THIS s.DOR & 0x03;
      if (!BX_FD_THIS s.pending_irq) {
        BX_FD_THIS s.status_reg0 = 0x80;
        BX_FD_THIS s.result_size = 1;
        }
      else {
        if (BX_FD_THIS s.reset_sensei > 0) {
          drive = 4 - BX_FD_THIS s.reset_sensei;
          BX_FD_THIS s.status_reg0 &= 0xfc;
          BX_FD_THIS s.status_reg0 |= drive;
          BX_FD_THIS s.reset_sensei--;
	  }
        BX_FD_THIS s.result[1] = BX_FD_THIS s.cylinder[drive];
        BX_FD_THIS s.result_size = 2;
        }
      BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
      BX_FD_THIS s.result_index = 0;
      if (!BX_FD_THIS s.reset_sensei) BX_FD_THIS s.status_reg0 = 0;

      /* read ready */
      BX_FD_THIS s.main_status_reg &= 0x0f;
      BX_FD_THIS s.main_status_reg |= (FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY);
      BX_DEBUG(("sense interrupt status"));
      return;
      break;

    case 0x0f: /* seek */
      /* command:
       *   byte0 = 0F
       *   byte1 = drive & head select
       *   byte2 = cylinder number
       * execution:
       *   postion head over specified cylinder
       * result:
       *   no result bytes, issues an interrupt
       */
      drive = BX_FD_THIS s.command[1] & 0x03;
      BX_FD_THIS s.DOR &= 0xfc;
      BX_FD_THIS s.DOR |= drive;

      BX_FD_THIS s.head[drive] = (BX_FD_THIS s.command[1] >> 2) & 0x01;
      BX_FD_THIS s.cylinder[drive] = BX_FD_THIS s.command[2];
      if (drive > 1)
        BX_PANIC(("floppy_command(): seek: drive>1"));
      /* ??? should also check cylinder validity */
      bx_pc_system.activate_timer( BX_FD_THIS s.floppy_timer_index,
        bx_options.Ofloppy_command_delay->get (), 0 );
      /* data reg not ready, controller busy */
      BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
      BX_FD_THIS s.pending_command = 0x0f; /* seek pending */
      return;
      break;

    case 0x13: // Configure
      BX_DEBUG(("io: configure (mode=%02xh, pretrack=%02xh)",
(unsigned)(BX_FD_THIS s.command[2]), (unsigned)(BX_FD_THIS s.command[3]) ));
      BX_FD_THIS s.result_size = 0;
      BX_FD_THIS s.result_index = 0;
      BX_FD_THIS s.pending_command = 0;
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_BUSY;
      return;
      break;

    case 0x4a: // read ID
      drive = BX_FD_THIS s.command[1] & 0x03;
      BX_FD_THIS s.DOR &= 0xfc;
      BX_FD_THIS s.DOR |= drive;

      motor_on = (BX_FD_THIS s.DOR>>(drive+4)) & 0x01;
      if (motor_on == 0) {
        BX_ERROR(("floppy_command(): 0x4a: motor not on"));
        BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
        return;
        }
      if (drive > 1)
        BX_PANIC(("io: 4a: bad drive #"));
      BX_FD_THIS s.result_size = 7;
      BX_FD_THIS s.result_index = 0;
      // setting result[0] in timer handler
      BX_FD_THIS s.result[1] = BX_FD_THIS s.status_reg1;
      BX_FD_THIS s.result[2] = BX_FD_THIS s.status_reg2;
      BX_FD_THIS s.result[3] = BX_FD_THIS s.cylinder[drive];
      BX_FD_THIS s.result[4] = BX_FD_THIS s.head[drive];
      BX_FD_THIS s.result[5] = 1; /* sector at completion */
      BX_FD_THIS s.result[6] = 2; // sector size code
      bx_pc_system.activate_timer( BX_FD_THIS s.floppy_timer_index,
        bx_options.Ofloppy_command_delay->get (), 0 );
      /* data reg not ready, controller busy */
      BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
      BX_FD_THIS s.pending_command = 0x4a; /* read ID pending */
      return;
      break;

    case 0x4d: // format track
        drive = BX_FD_THIS s.command[1] & 0x03;
        BX_FD_THIS s.DOR &= 0xfc;
        BX_FD_THIS s.DOR |= drive;

        motor_on = (BX_FD_THIS s.DOR>>(drive+4)) & 0x01;
        if (motor_on == 0)
          BX_PANIC(("floppy_command(): format track: motor not on"));
        BX_FD_THIS s.head[drive] = (BX_FD_THIS s.command[1] >> 2) & 0x01;
        sector_size = BX_FD_THIS s.command[2];
        BX_FD_THIS s.format_count = BX_FD_THIS s.command[3];
        BX_FD_THIS s.format_fillbyte = BX_FD_THIS s.command[5];
        if (drive > 1)
          BX_PANIC(("format track: bad drive #%d", drive));

        if (sector_size != 0x02) { // 512 bytes
          BX_PANIC(("format track: sector_size not 512"));
          }
        if (BX_FD_THIS s.format_count != BX_FD_THIS s.media[drive].sectors_per_track) {
          BX_PANIC(("format track: wrong number of sectors/track"));
          }
        if ( BX_FD_THIS s.media_present[drive] == 0 ) {
          // media not in drive, return error
          BX_INFO(("attempt to format track with media not present"));
          BX_FD_THIS s.result_size = 7;
          BX_FD_THIS s.result_index = 0;
          BX_FD_THIS s.status_reg0 = 0x40 | (BX_FD_THIS s.head[drive]<<2) | drive; // abnormal termination
          BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
          BX_FD_THIS s.result[1] = 0x25; // 0010 0101
          BX_FD_THIS s.result[2] = 0x31; // 0011 0001
          // 4 result bytes are unused
          BX_FD_THIS s.pending_command = 0;
          BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY;
          raise_interrupt();
          return;
          }
        if (BX_FD_THIS s.media[drive].write_protected) {
          // media write-protected, return error
          BX_INFO(("attempt to format track with media write-protected"));
          BX_FD_THIS s.result_size = 7;
          BX_FD_THIS s.result_index = 0;
          BX_FD_THIS s.status_reg0 = 0x40 | (BX_FD_THIS s.head[drive]<<2) | drive; // abnormal termination
          BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
          BX_FD_THIS s.result[1] = 0x27; // 0010 0111
          BX_FD_THIS s.result[2] = 0x31; // 0011 0001
          // 4 result bytes are unused
          BX_FD_THIS s.pending_command = 0;
          BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY;
          raise_interrupt();
          return;
          }

      /* 4 header bytes per sector are required */
      BX_FD_THIS s.format_count <<= 2;

      BX_DMA_SET_DRQ(FLOPPY_DMA_CHAN, 1);

      /* data reg not ready, controller busy */
      BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
      BX_FD_THIS s.pending_command = 0x4d; /* format track pending */
      BX_DEBUG(("format track"));
      return;
      break;

    case 0x66: // read normal data, MT=0
    case 0xe6: // read normal data, MT=1
    case 0x45: // write normal data, MT=0
    case 0xc5: // write normal data, MT=1
      BX_FD_THIS s.multi_track = (BX_FD_THIS s.command[0] >> 7);
      if ( (BX_FD_THIS s.DOR & 0x08) == 0 )
        BX_PANIC(("read/write command with DMA and int disabled"));
      drive = BX_FD_THIS s.command[1] & 0x03;
      BX_FD_THIS s.DOR &= 0xfc;
      BX_FD_THIS s.DOR |= drive;

      motor_on = (BX_FD_THIS s.DOR>>(drive+4)) & 0x01;
      if (motor_on == 0)
        BX_PANIC(("floppy_command(): read/write: motor not on"));
      head = BX_FD_THIS s.command[3] & 0x01;
      cylinder = BX_FD_THIS s.command[2]; /* 0..79 depending */
      sector = BX_FD_THIS s.command[4];   /* 1..36 depending */
      eot = BX_FD_THIS s.command[6];      /* 1..36 depending */
      sector_size = BX_FD_THIS s.command[5];
      data_length = BX_FD_THIS s.command[8];
      BX_DEBUG(("read/write normal data"));
      BX_DEBUG(("BEFORE"));
      BX_DEBUG(("  drive    = %u", (unsigned) drive));
      BX_DEBUG(("  head     = %u", (unsigned) head));
      BX_DEBUG(("  cylinder = %u", (unsigned) cylinder));
      BX_DEBUG(("  sector   = %u", (unsigned) sector));
      BX_DEBUG(("  eot      = %u", (unsigned) eot));
      if (drive > 1)
        BX_PANIC(("io: bad drive #"));
      if (head > 1)
        BX_PANIC(("io: bad head #"));

      // check that head number in command[1] bit two matches the head
      // reported in the head number field.  Real floppy drives are
      // picky about this, as reported in SF bug #439945, (Floppy drive
      // read input error checking).
      if (head != (BX_FD_THIS s.command[1]>>2)&1) {
        BX_ERROR(("head number in command[1] doesn't match head field"));
        BX_FD_THIS s.result_size = 7;
        BX_FD_THIS s.result_index = 0;
        BX_FD_THIS s.status_reg0 = 0x40 | (BX_FD_THIS s.head[drive]<<2) | drive; // abnormal termination
        BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
        BX_FD_THIS s.result[1] = 0x04; // 0000 0100
        BX_FD_THIS s.result[2] = 0x00; // 0000 0000
        BX_FD_THIS s.result[3] = BX_FD_THIS s.cylinder[drive];
        BX_FD_THIS s.result[4] = BX_FD_THIS s.head[drive];
        BX_FD_THIS s.result[5] = BX_FD_THIS s.sector[drive];
        BX_FD_THIS s.result[6] = 2; // sector size = 512

        BX_FD_THIS s.pending_command = 0;
        BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY;
        raise_interrupt();
        return;
      }

      if ( BX_FD_THIS s.media_present[drive] == 0 ) {
        // media not in drive, return error

        BX_INFO(("attempt to read/write sector %u,"
                     " sectors/track=%u", (unsigned) sector,
                     (unsigned) BX_FD_THIS s.media[drive].sectors_per_track));
        BX_FD_THIS s.result_size = 7;
        BX_FD_THIS s.result_index = 0;
        BX_FD_THIS s.status_reg0 = 0x40 | (BX_FD_THIS s.head[drive]<<2) | drive; // abnormal termination
        BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
        BX_FD_THIS s.result[1] = 0x25; // 0010 0101
        BX_FD_THIS s.result[2] = 0x31; // 0011 0001
        BX_FD_THIS s.result[3] = BX_FD_THIS s.cylinder[drive];
        BX_FD_THIS s.result[4] = BX_FD_THIS s.head[drive];
        BX_FD_THIS s.result[5] = BX_FD_THIS s.sector[drive];
        BX_FD_THIS s.result[6] = 2; // sector size = 512

        BX_FD_THIS s.pending_command = 0;
        BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY;
        raise_interrupt();
        return;
        }

      if (sector_size != 0x02) { // 512 bytes
        BX_PANIC(("sector_size not 512"));
        }
      if ( cylinder >= BX_FD_THIS s.media[drive].tracks ) {
		BX_PANIC(("io: norm r/w parms out of range: sec#%02xh cyl#%02xh eot#%02h head#%02xh",
				(unsigned) sector, (unsigned) cylinder, (unsigned) eot,
				(unsigned) head));
        return;
      }

      if (sector > BX_FD_THIS s.media[drive].sectors_per_track) {
        // requested sector > last sector on track
        BX_INFO(("attempt to read/write sector %u,"
                     " sectors/track=%u", (unsigned) sector,
                     (unsigned) BX_FD_THIS s.media[drive].sectors_per_track));
        // set controller to where drive would have left off
        // after it discovered the sector was past EOT
        BX_FD_THIS s.cylinder[drive] = cylinder;
        BX_FD_THIS s.head[drive]     = head;
        BX_FD_THIS s.sector[drive]   = BX_FD_THIS s.media[drive].sectors_per_track;

        BX_FD_THIS s.result_size = 7;

        BX_FD_THIS s.result_index = 0;
        // 0100 0HDD abnormal termination
        BX_FD_THIS s.status_reg0 = 0x40 | (BX_FD_THIS s.head[drive]<<2) | drive;
        BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
        // 1000 0101 end of cyl/NDAT/NID
        BX_FD_THIS s.result[1] = 0x86;
        // 0000 0000
        BX_FD_THIS s.result[2] = 0x00;
        BX_FD_THIS s.result[3] = BX_FD_THIS s.cylinder[drive];
        BX_FD_THIS s.result[4] = BX_FD_THIS s.head[drive];
        BX_FD_THIS s.result[5] = BX_FD_THIS s.sector[drive];
        BX_FD_THIS s.result[6] = 2; // sector size = 512

        bx_pc_system.activate_timer( BX_FD_THIS s.floppy_timer_index,
          bx_options.Ofloppy_command_delay->get (), 0 );
        /* data reg not ready, controller busy */
        BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
        BX_FD_THIS s.pending_command = BX_FD_THIS s.command[0];
        return;
        }

#if 0
      if (eot != BX_FD_THIS s.media[drive].sectors_per_track)
        BX_DEBUG(("io: bad eot #%02xh", (unsigned) eot));
#endif

      if (cylinder != BX_FD_THIS s.cylinder[drive])
        BX_DEBUG(("io: cylinder request != current cylinder"));

      logical_sector = (cylinder * 2 * BX_FD_THIS s.media[drive].sectors_per_track) +
                       (head * BX_FD_THIS s.media[drive].sectors_per_track) +
                       (sector - 1);

      if (logical_sector >= BX_FD_THIS s.media[drive].sectors) {
        BX_PANIC(("io: logical sector out of bounds"));
        }

      BX_FD_THIS s.cylinder[drive] = cylinder;
      BX_FD_THIS s.sector[drive]   = sector;
      BX_FD_THIS s.head[drive]     = head;

      if ((BX_FD_THIS s.command[0] & 0x7f) == 0x66) { // read
        floppy_xfer(drive, logical_sector*512, BX_FD_THIS s.floppy_buffer,
                    512, FROM_FLOPPY);
        BX_FD_THIS s.floppy_buffer_index = 0;

        BX_DMA_SET_DRQ(FLOPPY_DMA_CHAN, 1);

        /* data reg not ready, controller busy */
        BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
        BX_FD_THIS s.pending_command = BX_FD_THIS s.command[0];
        return;
        }
      else if ((BX_FD_THIS s.command[0] & 0x7f) == 0x45) { // write
        BX_FD_THIS s.floppy_buffer_index = 0;

        BX_DMA_SET_DRQ(FLOPPY_DMA_CHAN, 1);

        /* data reg not ready, controller busy */
        BX_FD_THIS s.main_status_reg = FD_MS_BUSY;
        BX_FD_THIS s.pending_command = BX_FD_THIS s.command[0];
        return;
        }
      else
        BX_PANIC(("floppy_command(): unknown read/write command"));

      return;
      break;

    default: // invalid or unsupported command
      BX_FD_THIS s.result_size = 1;
      BX_FD_THIS s.result_index = 0;
      BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
      BX_FD_THIS s.status_reg0 = 0;
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY;
    }
#endif
}

  void
bx_floppy_ctrl_c::floppy_xfer(Bit8u drive, Bit32u offset, Bit8u *buffer,
            Bit32u bytes, Bit8u direction)
{
  int ret;

  if (drive > 1)
    BX_PANIC(("floppy_xfer: drive > 1"));

  if (bx_dbg.floppy) {
    BX_INFO(("drive=%u", (unsigned) drive));
    BX_INFO(("offset=%u", (unsigned) offset));
    BX_INFO(("bytes=%u", (unsigned) bytes));
    BX_INFO(("direction=%s", (direction==FROM_FLOPPY)? "from" : "to"));
    }

#if BX_WITH_MACOS
  if (strcmp(bx_options.floppya.Opath->getptr (), SuperDrive))
#endif
    {
    ret = lseek(BX_FD_THIS s.media[drive].fd, offset, SEEK_SET);
    if (ret < 0) {
      BX_PANIC(("could not perform lseek() on floppy image file"));
      }
    }

  if (direction == FROM_FLOPPY) {
#if BX_WITH_MACOS
    if (!strcmp(bx_options.floppya.Opath->getptr (), SuperDrive))
      ret = fd_read((char *) buffer, offset, bytes);
    else
#endif
      ret = ::read(BX_FD_THIS s.media[drive].fd, (bx_ptr_t) buffer, bytes);
    if (ret < int(bytes)) {
      /* ??? */
      if (ret > 0) {
        BX_INFO(("partial read() on floppy image returns %u/%u",
          (unsigned) ret, (unsigned) bytes));
        memset(buffer + ret, 0, bytes - ret);
        }
      else {
        BX_INFO(("read() on floppy image returns 0"));
        memset(buffer, 0, bytes);
        }
      }
    }

  else { // TO_FLOPPY
    BX_ASSERT (!BX_FD_THIS s.media[drive].write_protected);
#if BX_WITH_MACOS
    if (!strcmp(bx_options.floppya.Opath->getptr (), SuperDrive))
      ret = fd_write((char *) buffer, offset, bytes);
    else
#endif
      ret = ::write(BX_FD_THIS s.media[drive].fd, (bx_ptr_t) buffer, bytes);
    if (ret < int(bytes)) {
      BX_PANIC(("could not perform write() on floppy image file"));
    }
  }
}



  void
bx_floppy_ctrl_c::timer_handler(void *this_ptr)
{

  bx_floppy_ctrl_c *class_ptr = (bx_floppy_ctrl_c *) this_ptr;

  class_ptr->timer();
}

  void
bx_floppy_ctrl_c::timer()
{
  Bit8u drive;

  drive = BX_FD_THIS s.DOR & 0x03;
  switch ( BX_FD_THIS s.pending_command ) {
    case 0x07: // recal
      BX_FD_THIS s.pending_command = 0;
      /* write ready, not busy */
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | (1 << drive);
      BX_FD_THIS s.status_reg0 = 0x20 | drive;
      raise_interrupt();
      goto reset_changeline;
      break;

    case 0x0f: // seek
      BX_FD_THIS s.pending_command = 0;
      /* write ready, not busy */
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | (1 << drive);
      BX_FD_THIS s.status_reg0 = 0x20 | drive;
      raise_interrupt();
      goto reset_changeline;
      break;

    case 0x4a: /* read ID */
      BX_FD_THIS s.pending_command = 0;
      /* read ready, busy */
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO;
      BX_FD_THIS s.status_reg0 = 0x20 | drive;
      BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
      raise_interrupt();
      break;

    case 0x66: // read normal data
    case 0xe6:
    case 0x45: // write normal data
    case 0xc5:
      BX_FD_THIS s.pending_command = 0;
      /* read ready, busy */
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY | (1 << drive);
      BX_FD_THIS s.status_reg0 = 0x20 | drive;
      raise_interrupt();
      break;

    case 0xfe: // (contrived) RESET
      reset(BX_RESET_SOFTWARE);
      BX_FD_THIS s.pending_command = 0;
      BX_FD_THIS s.status_reg0 = 0xc0;
      raise_interrupt();
      BX_FD_THIS s.reset_sensei = 4;
      break;
    
    case 0x00: // nothing pending?
      break;

    default:
      BX_PANIC(("floppy:timer(): unknown case %02x",
        (unsigned) BX_FD_THIS s.pending_command));
    }
  return;

reset_changeline:
  if (drive > 1) return;
  if (BX_FD_THIS s.media_present[drive])
    BX_FD_THIS s.DIR &= ~0x80; // clear disk change line
}

  void
bx_floppy_ctrl_c::dma_write(Bit8u *data_byte)
{
  // A DMA write is from I/O to Memory
  // We need to return then next data byte from the floppy buffer
  // to be transfered via the DMA to memory. (read block from floppy)


  *data_byte = BX_FD_THIS s.floppy_buffer[BX_FD_THIS s.floppy_buffer_index++];

  if (BX_FD_THIS s.floppy_buffer_index >= 512) {
    Bit8u drive;

    drive = BX_FD_THIS s.DOR & 0x03;
    increment_sector(); // increment to next sector before retrieving next one
    BX_FD_THIS s.floppy_buffer_index = 0;
    if (BX_DMA_GET_TC()) { // Terminal Count line, done
      BX_FD_THIS s.pending_command = 0;
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY | (1 << drive);
      BX_FD_THIS s.result_size = 7;
      BX_FD_THIS s.result_index = 0;
      BX_FD_THIS s.status_reg0 = 0x20 | (BX_FD_THIS s.head[drive] << 2) | drive;
      BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
      BX_FD_THIS s.result[1] = 0;
      BX_FD_THIS s.result[2] = 0;
      BX_FD_THIS s.result[3] = BX_FD_THIS s.cylinder[drive];
      BX_FD_THIS s.result[4] = BX_FD_THIS s.head[drive];
      BX_FD_THIS s.result[5] = BX_FD_THIS s.sector[drive];
      BX_FD_THIS s.result[6] = 2;

      if (bx_dbg.floppy) {
        BX_INFO(("<<READ DONE>>"));
        BX_INFO(("AFTER"));
        BX_INFO(("  drive    = %u", (unsigned) drive));
        BX_INFO(("  head     = %u", (unsigned) BX_FD_THIS s.head[drive]));
        BX_INFO(("  cylinder = %u", (unsigned) BX_FD_THIS s.cylinder[drive]));
        BX_INFO(("  sector   = %u", (unsigned) BX_FD_THIS s.sector[drive]));
        }

      raise_interrupt();
      BX_DMA_SET_DRQ(FLOPPY_DMA_CHAN, 0);
      }
    else { // more data to transfer
      Bit32u logical_sector;
      logical_sector = (BX_FD_THIS s.cylinder[drive] * 2 *
                        BX_FD_THIS s.media[drive].sectors_per_track) +
                       (BX_FD_THIS s.head[drive] *
                        BX_FD_THIS s.media[drive].sectors_per_track) +
                       (BX_FD_THIS s.sector[drive] - 1);
      floppy_xfer(drive, logical_sector*512, BX_FD_THIS s.floppy_buffer,
                  512, FROM_FLOPPY);
      }
    }
}

  void
bx_floppy_ctrl_c::dma_read(Bit8u *data_byte)
{
  // A DMA read is from Memory to I/O
  // We need to write the data_byte which was already transfered from memory
  // via DMA to I/O (write block to floppy)

  Bit8u drive;
  Bit32u logical_sector;

  drive = BX_FD_THIS s.DOR & 0x03;
  if (BX_FD_THIS s.pending_command == 0x4d) { // format track in progress
    --BX_FD_THIS s.format_count;
    switch (3 - (BX_FD_THIS s.format_count & 0x03)) {
      case 0:
        BX_FD_THIS s.cylinder[drive] = *data_byte;
        break;
      case 1:
        if (*data_byte != BX_FD_THIS s.head[drive])
          BX_ERROR(("head number does not match head field"));
        break;
      case 2:
        BX_FD_THIS s.sector[drive] = *data_byte;
        break;
      case 3:
        if (*data_byte != 2) BX_ERROR(("sector size code not 2"));
        BX_DEBUG(("formatting cylinder %u head %u sector %u",
                  BX_FD_THIS s.cylinder[drive], BX_FD_THIS s.head[drive],
                  BX_FD_THIS s.sector[drive]));
        for (unsigned i = 0; i < 512; i++) {
          BX_FD_THIS s.floppy_buffer[i] = BX_FD_THIS s.format_fillbyte;
          }
        logical_sector = (BX_FD_THIS s.cylinder[drive] * 2 * BX_FD_THIS s.media[drive].sectors_per_track) +
                         (BX_FD_THIS s.head[drive] * BX_FD_THIS s.media[drive].sectors_per_track) +
                         (BX_FD_THIS s.sector[drive] - 1);
        floppy_xfer(drive, logical_sector*512, BX_FD_THIS s.floppy_buffer,
                    512, TO_FLOPPY);
        break;
      }
    if ((BX_FD_THIS s.format_count == 0) || (BX_DMA_GET_TC())) {
      BX_FD_THIS s.format_count = 0;
      BX_FD_THIS s.pending_command = 0;
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY | (1 << drive);
      BX_FD_THIS s.result_size = 7;
      BX_FD_THIS s.result_index = 0;
      BX_FD_THIS s.status_reg0 = (BX_FD_THIS s.head[drive] << 2) | drive;
      BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
      BX_FD_THIS s.result[1] = BX_FD_THIS s.status_reg1;
      BX_FD_THIS s.result[2] = BX_FD_THIS s.status_reg2;
      // 4 result bytes are unused
      raise_interrupt();
      BX_DMA_SET_DRQ(FLOPPY_DMA_CHAN, 0);
      }
    return;
    }

  BX_FD_THIS s.floppy_buffer[BX_FD_THIS s.floppy_buffer_index++] = *data_byte;

  if (BX_FD_THIS s.floppy_buffer_index >= 512) {
    logical_sector = (BX_FD_THIS s.cylinder[drive] * 2 * BX_FD_THIS s.media[drive].sectors_per_track) +
                     (BX_FD_THIS s.head[drive] * BX_FD_THIS s.media[drive].sectors_per_track) +
                     (BX_FD_THIS s.sector[drive] - 1);
  if ( BX_FD_THIS s.media[drive].write_protected ) {
    // write protected error
    BX_INFO(("tried to write disk %u, which is write-protected", drive));
    BX_FD_THIS s.result_size = 7;
    BX_FD_THIS s.result_index = 0;
    // ST0: IC1,0=01  (abnormal termination: started execution but failed)
    BX_FD_THIS s.result[0] = 0x40 | (BX_FD_THIS s.head[drive]<<2) | drive;
    // ST1: DataError=1, NDAT=1, NotWritable=1, NID=1
    BX_FD_THIS s.result[1] = 0x27; // 0010 0111
    // ST2: CRCE=1, SERR=1, BCYL=1, NDAM=1.
    BX_FD_THIS s.result[2] = 0x31; // 0011 0001
    BX_FD_THIS s.result[3] = BX_FD_THIS s.cylinder[drive];
    BX_FD_THIS s.result[4] = BX_FD_THIS s.head[drive];
    BX_FD_THIS s.result[5] = BX_FD_THIS s.sector[drive];
    BX_FD_THIS s.result[6] = 2; // sector size = 512

    BX_FD_THIS s.pending_command = 0;
    BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY | (1 << drive);
    raise_interrupt();
    return;
    }
    floppy_xfer(drive, logical_sector*512, BX_FD_THIS s.floppy_buffer,
                512, TO_FLOPPY);
    increment_sector(); // increment to next sector after writing current one
    BX_FD_THIS s.floppy_buffer_index = 0;
    if (BX_DMA_GET_TC()) { // Terminal Count line, done
      BX_FD_THIS s.pending_command = 0;
      BX_FD_THIS s.main_status_reg = FD_MS_MRQ | FD_MS_DIO | FD_MS_BUSY;
      BX_FD_THIS s.result_size = 7;
      BX_FD_THIS s.result_index = 0;
      BX_FD_THIS s.status_reg0 = 0x20 | (BX_FD_THIS s.head[drive] << 2) | drive;
      BX_FD_THIS s.result[0] = BX_FD_THIS s.status_reg0;
      BX_FD_THIS s.result[1] = 0;
      BX_FD_THIS s.result[2] = 0;
      BX_FD_THIS s.result[3] = BX_FD_THIS s.cylinder[drive];
      BX_FD_THIS s.result[4] = BX_FD_THIS s.head[drive];
      BX_FD_THIS s.result[5] = BX_FD_THIS s.sector[drive];
      BX_FD_THIS s.result[6] = 2;
      if (bx_dbg.floppy) {
        BX_INFO(("<<WRITE DONE>>"));
        BX_INFO(("AFTER"));
        BX_INFO(("  drive    = %u", (unsigned) drive));
        BX_INFO(("  head     = %u", (unsigned) BX_FD_THIS s.head[drive]));
        BX_INFO(("  cylinder = %u", (unsigned) BX_FD_THIS s.cylinder[drive]));
        BX_INFO(("  sector   = %u", (unsigned) BX_FD_THIS s.sector[drive]));
        }

      raise_interrupt();
      BX_DMA_SET_DRQ(FLOPPY_DMA_CHAN, 0);
      }
    else { // more data to transfer
      } // else
    } // if BX_FD_THIS s.floppy_buffer_index >= 512
}

  void
bx_floppy_ctrl_c::raise_interrupt(void)
{
  BX_FD_THIS devices->pic->raise_irq(6);
  BX_FD_THIS s.pending_irq = 1;
  BX_FD_THIS s.reset_sensei = 0;
}


  void
bx_floppy_ctrl_c::increment_sector(void)
{
  Bit8u drive;

  drive = BX_FD_THIS s.DOR & 0x03;

  // values after completion of data xfer
  // ??? calculation depends on base_count being multiple of 512
  BX_FD_THIS s.sector[drive] ++;
  if (BX_FD_THIS s.sector[drive] > BX_FD_THIS s.media[drive].sectors_per_track) {
    BX_FD_THIS s.sector[drive] = 1;
    if (BX_FD_THIS s.multi_track) {
      BX_FD_THIS s.head[drive] ++;
      if (BX_FD_THIS s.head[drive] > 1) {
        BX_FD_THIS s.head[drive] = 0;
        BX_FD_THIS s.cylinder[drive] ++;
        }
      }
    else {
      BX_FD_THIS s.cylinder[drive] ++;
      }
    if (BX_FD_THIS s.cylinder[drive] >= BX_FD_THIS s.media[drive].tracks) {
      // Set to 1 past last possible cylinder value.
      // I notice if I set it to tracks-1, prama linux won't boot.
      BX_FD_THIS s.cylinder[drive] = BX_FD_THIS s.media[drive].tracks;
      BX_INFO(("increment_sector: clamping cylinder to max"));
      }
    }
}

  unsigned
bx_floppy_ctrl_c::set_media_status(unsigned drive, unsigned status)
{
  char *path;
  unsigned type;

  // if setting to the current value, nothing to do
  if (status == BX_FD_THIS s.media_present[drive])
    return(status);

  if (status == 0) {
    // eject floppy
    if (BX_FD_THIS s.media[drive].fd >= 0) {
      close( BX_FD_THIS s.media[drive].fd );
      BX_FD_THIS s.media[drive].fd = -1;
      }
    BX_FD_THIS s.media_present[drive] = 0;
    if (drive == 0) {
      bx_options.floppya.Oinitial_status->set(BX_EJECTED);
    } else {
      bx_options.floppyb.Oinitial_status->set(BX_EJECTED);
    }
    BX_FD_THIS s.DIR |= 0x80; // disk changed line
    return(0);
    }
  else {
    // insert floppy
    if (drive == 0) {
      path = bx_options.floppya.Opath->getptr ();
      type = bx_options.floppya.Otype->get ();
      }
    else {
      path = bx_options.floppyb.Opath->getptr ();
      type = bx_options.floppyb.Otype->get ();
      }
    if (evaluate_media(type, path, & BX_FD_THIS s.media[drive])) {
      BX_FD_THIS s.media_present[drive] = 1;
      if (drive == 0) {
        bx_options.floppya.Oinitial_status->set(BX_INSERTED);
      } else {
        bx_options.floppyb.Oinitial_status->set(BX_INSERTED);
      }
      BX_FD_THIS s.DIR |= 0x80; // disk changed line
      return(1);
      }
    else {
      BX_FD_THIS s.media_present[drive] = 0;
      if (drive == 0) {
        bx_options.floppya.Oinitial_status->set(BX_EJECTED);
      } else {
        bx_options.floppyb.Oinitial_status->set(BX_EJECTED);
      }
      return(0);
      }
    }
}

  unsigned
bx_floppy_ctrl_c::get_media_status(unsigned drive)
{
  return( BX_FD_THIS s.media_present[drive] );
}

#ifdef O_BINARY
#define BX_RDONLY O_RDONLY | O_BINARY
#define BX_RDWR O_RDWR | O_BINARY
#else
#define BX_RDONLY O_RDONLY
#define BX_RDWR O_RDWR
#endif

  Boolean
bx_floppy_ctrl_c::evaluate_media(unsigned type, char *path, floppy_t *media)
{
  struct stat stat_buf;
  int ret;
#if BX_WITH_WIN32
  char sTemp[1024];
#endif

  if (type == BX_FLOPPY_NONE)
    return(0);

  //If media file is already open, close it before reopening.
  if(media->fd >=0) {
    close(media->fd);
    media->fd=-1;
  }

  // open media file (image file or device)
  media->write_protected = 0;
#ifdef macintosh
  media->fd = 0;
  if (strcmp(bx_options.floppya.Opath->getptr (), SuperDrive))
#endif
#if BX_WITH_WIN32
    if ( (path[1] == ':') && (strlen(path) == 2) ) {
	  wsprintf(sTemp, "\\\\.\\%s", path);
	  media->fd = open(sTemp, BX_RDWR);
	} else {
		media->fd = open(path, BX_RDWR);
	} 
#else
    media->fd = open(path, BX_RDWR);
#endif

  if (media->fd < 0) {
    BX_INFO(( "tried to open %s read/write: %s",path,strerror(errno) ));
    // try opening the file read-only
    media->write_protected = 1;
#ifdef macintosh
  media->fd = 0;
  if (strcmp(bx_options.floppya.Opath->getptr (), SuperDrive))
#endif
#if BX_WITH_WIN32
    if ( (path[1] == ':') && (strlen(path) == 2) ) {
	  wsprintf(sTemp, "\\\\.\\%s", path);
	  media->fd = open(sTemp, BX_RDONLY);
	} else {
		media->fd = open(path, BX_RDONLY);
	}
#else
    media->fd = open(path, BX_RDONLY);
#endif
    if (media->fd < 0) {
      // failed to open read-only too
      BX_INFO(( "tried to open %s read only: %s",path,strerror(errno) ));
      return(0);
    }
  }

#if BX_WITH_MACOS
  if (!strcmp(bx_options.floppya.Opath->getptr (), SuperDrive))
    ret = fd_stat(&stat_buf);
  else
    ret = fstat(media->fd, &stat_buf);
#elif BX_WITH_WIN32
//  if ( (path[1] == ':') && (strlen(path) == 2) ) {
    stat_buf.st_mode = S_IFCHR;
    // maybe replace with code that sets ret to -1 if the disk is not available
    ret = 0;
//  } else {
	// put code here for disk images
//	ret = fstat(media->fd, &stat_buf);
//  }
#else
  // unix
  ret = fstat(media->fd, &stat_buf);
#endif
  if (ret) {
    BX_PANIC(("fstat floppy 0 drive image file returns error: %s", strerror(errno)));
    return(0);
    }

  if ( S_ISREG(stat_buf.st_mode) ) {
    // regular file
    switch (type) {
      case BX_FLOPPY_720K: // 720K 3.5"
        media->type              = BX_FLOPPY_720K;
        media->sectors_per_track = 9;
        media->tracks            = 80;
        media->heads             = 2;
        break;
      case BX_FLOPPY_1_2: // 1.2M 5.25"
        media->type              = BX_FLOPPY_1_2;
        media->sectors_per_track = 15;
        media->tracks            = 80;
        media->heads             = 2;
        break;
      case BX_FLOPPY_1_44: // 1.44M 3.5"
        media->type              = BX_FLOPPY_1_44;
        if (stat_buf.st_size <= 1474560) {
          media->sectors_per_track = 18;
          media->tracks            = 80;
          media->heads             = 2;
          }
        else if (stat_buf.st_size == 1720320) {
          media->sectors_per_track = 21;
          media->tracks            = 80;
          media->heads             = 2;
          }
	else if (stat_buf.st_size == 1763328) {
          media->sectors_per_track = 21;
          media->tracks            = 82;
          media->heads             = 2;
	  }
        else {
          BX_INFO(("evaluate_media: file '%s' of unknown size %lu",
            path, (unsigned long) stat_buf.st_size));
          return(0);
          }
        break;
      case BX_FLOPPY_2_88: // 2.88M 3.5"
        media->type              = BX_FLOPPY_2_88;
        media->sectors_per_track = 36;
        media->tracks            = 80;
        media->heads             = 2;
        break;
      default:
        BX_PANIC(("evaluate_media: unknown media type"));
      }
    media->sectors = media->heads * media->tracks * media->sectors_per_track;
    return(1); // success
    }

  else if ( S_ISCHR(stat_buf.st_mode)
#if BX_WITH_MACOS == 0
#ifdef S_ISBLK
            || S_ISBLK(stat_buf.st_mode)
#endif
#endif
           ) {
    // character or block device
    // assume media is formatted to typical geometry for drive
    switch (type) {
      case BX_FLOPPY_720K: // 720K 3.5"
        media->type              = BX_FLOPPY_720K;
        media->sectors_per_track = 9;
        media->tracks            = 80;
        media->heads             = 2;
        break;
      case BX_FLOPPY_1_2: // 1.2M 5.25"
        media->type              = BX_FLOPPY_1_2;
        media->sectors_per_track = 15;
        media->tracks            = 80;
        media->heads             = 2;
        break;
      case BX_FLOPPY_1_44: // 1.44M 3.5"
        media->type              = BX_FLOPPY_1_44;
        media->sectors_per_track = 18;
        media->tracks            = 80;
        media->heads             = 2;
        break;
      case BX_FLOPPY_2_88: // 2.88M 3.5"
        media->type              = BX_FLOPPY_2_88;
        media->sectors_per_track = 36;
        media->tracks            = 80;
        media->heads             = 2;
        break;
      default:
        BX_PANIC(("evaluate_media: unknown media type"));
      }
    media->sectors = media->heads * media->tracks * media->sectors_per_track;
    return(1); // success
    }
  else {
    // unknown file type
    BX_INFO(("unknown mode type"));
    return(0);
    }
}