disk_pravetz.c

/*
**  Oricutron
**  Copyright (C) 2009-2014 Peter Gordon
**
**  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, version 2
**  of the License.
**
**  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, Fifth Floor, Boston, MA  02110-1301, USA.
**
 */

/*
**  Pravetz 8D disk drive emulation
**  Copyright (C) 2009-2013 iss
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "system.h"
#include "6502.h"
#include "via.h"
#include "8912.h"
#include "gui.h"
#include "disk.h"
#include "disk_pravetz.h"
#include "monitor.h"
#include "6551.h"
#include "machine.h"

#define GENERAL_DISK_DEBUG 0

#if GENERAL_DISK_DEBUG
static int last_track = -1;
static int last_sector = -1;
#endif

static Uint8  disk_pravetz_read_selected(struct machine *oric);
static void   disk_pravetz_write_selected(struct machine *oric, Uint8 data);
static void   disk_pravetz_switch(struct machine *oric, Uint16 addr);

Uint8 disk_pravetz_read(struct machine *oric, Uint16 addr)
{
    disk_pravetz_switch(oric, addr-PRAV_DISK_OFFSET);
    /* odd addresses don't produce anything */
    return (!(addr & 1))? disk_pravetz_read_selected(oric) : 0;
}

void disk_pravetz_write(struct machine *oric, Uint16 addr, Uint8 data)
{
    disk_pravetz_switch(oric, addr-PRAV_DISK_OFFSET);
    /* even addresses don't write anything */
    if(addr & 1)
    {
        disk_pravetz_write_selected(oric, data);
    }
}

/* Skewing-Table */
static int interleave[16] =
{
    0, 7, 14, 6, 13, 5, 12, 4, 11, 3, 10, 2, 9, 1, 8, 15
};

/* Translation Table */
static int  translate[256] =
{
    0x96, 0x97, 0x9a, 0x9b, 0x9d, 0x9e, 0x9f, 0xa6,
    0xa7, 0xab, 0xac, 0xad, 0xae, 0xaf, 0xb2, 0xb3,
    0xb4, 0xb5, 0xb6, 0xb7, 0xb9, 0xba, 0xbb, 0xbc,
    0xbd, 0xbe, 0xbf, 0xcb, 0xcd, 0xce, 0xcf, 0xd3,
    0xd6, 0xd7, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde,
    0xdf, 0xe5, 0xe6, 0xe7, 0xe9, 0xea, 0xeb, 0xec,
    0xed, 0xee, 0xef, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6,
    0xf7, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x00, 0x01,
    0x80, 0x80, 0x02, 0x03, 0x80, 0x04, 0x05, 0x06,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x07, 0x08,
    0x80, 0x80, 0x80, 0x09, 0x0a, 0x0b, 0x0c, 0x0d,
    0x80, 0x80, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13,
    0x80, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
    0x80, 0x80, 0x80, 0x1b, 0x80, 0x1c, 0x1d, 0x1e,
    0x80, 0x80, 0x80, 0x1f, 0x80, 0x80, 0x20, 0x21,
    0x80, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
    0x80, 0x80, 0x80, 0x80, 0x80, 0x29, 0x2a, 0x2b,
    0x80, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32,
    0x80, 0x80, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
    0x80, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f
};

static void  disk_pravetz_update_position (struct pravetz_drive *drv)
{
    if (drv->motor_on)
    {
        drv->byte = (1 + drv->byte) % PRAV_RAW_TRACK_SIZE;
    }
}

Uint8  disk_pravetz_image_raw_byte(struct machine *oric, int drive,  Uint16 t_idx, Uint16 s_idx, Uint16 b_idx)
{
    long  f_pos;

    static Uint8  old;
    static Uint8  eor;
    static Uint8  raw;
    static Uint8  check;

    struct pravetz_drive *drv = &oric->pravetz.drv[drive];

    raw = 0xFF;

    switch (b_idx)
    {
    case 0:
    case 1:
    case 2:
    case 3:
    case 4:
    case 5:
    case 20:
    case 21:
    case 22:
    case 23:
    case 24:
        /* sync bytes */
        return 0xFF;

    case 6:
    case 25:
        /* sector header byte #1 */
        return 0xD5;

    case 7:
    case 26:
        /* sector header byte #2 */
        return 0xAA;

    case 8:
        /* address header byte */
        return 0x96;

    case 9:
        /* volume byte #1 */
        check = drv->volume;
        return 0xAA | (drv->volume >> 1);

    case 10:
        /* volume */
        return 0xAA | drv->volume;

    case 11:
        /* track byte #1 */
        check ^= t_idx;
        return 0xAA | (t_idx >> 1);

    case 12:
        /* track byte #2 */
        return 0xAA | t_idx;

    case 13:
        /* sector byte #1 */
        check ^= s_idx;
        return 0xAA | (s_idx >> 1);

    case 14:
        /* sector byte #2 */
        return 0xAA | s_idx;

    case 15:
        /* checksum byte #1 */
        return 0xAA | (check >> 1);

    case 16:
        /* checksum byte #2 */
        return 0xAA | check;

    case 17:
    case 371:
        /* address/data trailer byte #1 */
        return 0xDE;

    case 18:
    case 372:
        /* address/data trailer byte #2 */
        return 0xAA;

    case 19:
    case 373:
        /* address/data trailer byte #3 */
        return 0xEB;

    case 27:
        /* data header */
        eor = 0;

        /* Read the coming sector */
        f_pos = (256 * 16 * t_idx) + (256 * interleave[s_idx]);
        if (drv->pimg)
          drv->sector_ptr = &drv->pimg->rawimage[f_pos];
        else
          drv->sector_ptr = NULL;
        return 0xAD;

    case 370:
        /* checksum */
        return translate[eor & 0x3F];

    default:
        b_idx -= 28;

        if (b_idx >= 0x56)
        {
            /* 6 Bit */
            old  = drv->sector_ptr[b_idx - 0x56];
            old  = old >> 2;
            eor ^= old;
            raw  = translate[eor & 0x3F];
            eor  = old;
        }
        else
        {
            /* 3 * 2 Bit */
            old  = (drv->sector_ptr[b_idx] & 0x01) << 1;
            old |= (drv->sector_ptr[b_idx] & 0x02) >> 1;
            old |= (drv->sector_ptr[b_idx + 0x56] & 0x01) << 3;
            old |= (drv->sector_ptr[b_idx + 0x56] & 0x02) << 1;
            old |= (drv->sector_ptr[b_idx + 0xAC] & 0x01) << 5;
            old |= (drv->sector_ptr[b_idx + 0xAC] & 0x02) << 3;
            eor ^= old;
            raw  = translate[eor & 0x3F];
            eor  = old;
        }
        break;
    }

    return raw;
}


/**
** Returns the next byte from the 'disk'
*/

static Uint8  disk_pravetz_readbyte(struct machine *oric)
{
    struct pravetz_drive *drv = &oric->pravetz.drv[oric->wddisk.c_drive];

    /* make sure there's a 'disk in the drive' */
    if (!drv->pimg)
        return 0xFF;

    disk_pravetz_update_position(drv);

    /**/
#if GENERAL_DISK_DEBUG
    if(last_sector != drv->byte / PRAV_RAW_BYTES_PER_SECTOR || last_track != drv->half_track)
    {
      printf("{R} fdu: T:%.2d S:%.2X.%.3d [%.2X]\n",
            drv->half_track / 2,
            drv->byte / PRAV_RAW_BYTES_PER_SECTOR,
            drv->byte % PRAV_RAW_BYTES_PER_SECTOR,
            drv->image[drv->half_track / 2][drv->byte]);
      last_sector = drv->byte / PRAV_RAW_BYTES_PER_SECTOR;
      last_track = drv->half_track;
    }
#endif
    /**/

    return drv->image[drv->half_track / 2][drv->byte];
}

/**
** Returns the appropriate disk controller (IWM) register based on the
** state of the Q6 and Q7 select bits.
*/

static Uint8 disk_pravetz_read_selected(struct machine *oric)
{
    struct pravetz_drive *drv = &oric->pravetz.drv[oric->wddisk.c_drive];

    if (!drv->write_ready)
    {
        drv->write_ready = 0x80;
    }

    switch (drv->select)
    {
    case 0:
        return disk_pravetz_readbyte(oric);

    case 1:
        return drv->prot | drv->motor_on;

    case 2:
        return drv->write_ready;
    }

    return 0;
}

static Uint8 temp_sector_buffer[PRAV_BYTES_PER_SECTOR + 2];

void disk_pravetz_write_image(struct pravetz_drive *d_ptr)
{
    Uint8   eor;
    Uint8   s_idx;

    int  sector_search_count;

    int  t_idx;
    int  b_idx;
    int  tb_idx;
    int  sector_count, f_pos;

    if (!d_ptr)
      return;
    
    if (!d_ptr->dirty)
      return;
    
    tb_idx = 0;
    for (t_idx = 0; t_idx < PRAV_TRACKS_PER_DISK; t_idx++)
    {
        sector_count = 16;

find_sector:

        /* look for the sector header */

        sector_search_count = 0;
        while (0xD5 != d_ptr->image[t_idx][tb_idx])
        {
            tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
            if (++sector_search_count > PRAV_RAW_TRACK_SIZE) return;
        }

        tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
        if (0xAA != d_ptr->image[t_idx][tb_idx])
        {
            tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
            goto find_sector;
        }

        tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
        if (0x96 != d_ptr->image[t_idx][tb_idx])
        {
            tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
            goto find_sector;
        }

        /* found the sector header */

        /* skip 'volume' and 'track' */
        tb_idx = (tb_idx + 5) % PRAV_RAW_TRACK_SIZE;

        /* sector byte #1 */
        s_idx  = 0x55 | (d_ptr->image[t_idx][tb_idx] << 1);
        tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
        s_idx &= d_ptr->image[t_idx][tb_idx];
        tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;

        /* look for the sector data */

        while (0xD5 != d_ptr->image[t_idx][tb_idx])
            tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;

        tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
        if (0xAA != d_ptr->image[t_idx][tb_idx])
        {
            tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
            goto find_sector;
        }

        tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
        if (0xAD != d_ptr->image[t_idx][tb_idx])
        {
            tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
            goto find_sector;
        }

        /* found the sector data */

        tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;
        eor = 0;

        for (b_idx = 0; b_idx < 342; b_idx++)
        {
            eor ^= translate[d_ptr->image[t_idx][tb_idx]];
            tb_idx = (tb_idx + 1) % PRAV_RAW_TRACK_SIZE;

            if (b_idx >= 0x56)
            {
                /* 6 Bit */
                temp_sector_buffer[b_idx - 0x56] |= (eor << 2);
            }
            else
            {
                /* 3 * 2 Bit */
                temp_sector_buffer[b_idx]         = (eor & 0x01) << 1;
                temp_sector_buffer[b_idx]        |= (eor & 0x02) >> 1;
                temp_sector_buffer[b_idx + 0x56]  = (eor & 0x04) >> 1;
                temp_sector_buffer[b_idx + 0x56] |= (eor & 0x08) >> 3;
                temp_sector_buffer[b_idx + 0xAC]  = (eor & 0x10) >> 3;
                temp_sector_buffer[b_idx + 0xAC] |= (eor & 0x20) >> 5;
            }
        }

        /* write the sector */
        f_pos = (PRAV_BYTES_PER_SECTOR * PRAV_SECTORS_PER_TRACK * t_idx) +
                (PRAV_BYTES_PER_SECTOR * interleave[s_idx]);

        memcpy(&d_ptr->pimg->rawimage[f_pos], temp_sector_buffer, PRAV_BYTES_PER_SECTOR);
        d_ptr->pimg->modified = SDL_TRUE;
        d_ptr->pimg->modified_time = 0;
        sector_count--;

        if (sector_count)
            goto find_sector;
    }

    d_ptr->dirty = SDL_FALSE;
}

/**
** Writes a byte to the next position on the 'disk'
*/

static void  disk_pravetz_writebyte(struct machine *oric, Uint8  w_byte)
{
    struct pravetz_drive *drv = &oric->pravetz.drv[oric->wddisk.c_drive];
    disk_pravetz_update_position(drv);

    /* make sure there's a 'disk in the drive' */
    if (!drv->pimg)
        return;

    if (drv->prot)
        return;

    /* don't allow impossible bytes */
    if (w_byte < 0x96)
        return;

    drv->dirty = SDL_TRUE;
    drv->image[drv->half_track / 2][drv->byte] = w_byte;

    /**/
#if GENERAL_DISK_DEBUG
    if(last_sector != drv->byte / PRAV_RAW_BYTES_PER_SECTOR || last_track != drv->half_track)
    {
      printf("{W} fdu: T:%.2d S:%.2X.%.3d [%.2X]\n",
            drv->half_track / 2,
            drv->byte / PRAV_RAW_BYTES_PER_SECTOR,
            drv->byte % PRAV_RAW_BYTES_PER_SECTOR,
            w_byte);
      last_sector = drv->byte / PRAV_RAW_BYTES_PER_SECTOR;
      last_track = drv->half_track;
    }
#endif
    /**/
}

/**
** Writes to the appropriate disk controller (IWM) register based on the
** state of the Q6 and Q7 select bits.
*/

static void  disk_pravetz_write_selected(struct machine *oric, Uint8  w_byte)
{
    struct pravetz_drive *drv = &oric->pravetz.drv[oric->wddisk.c_drive];

    if (3 == drv->select)
    {
        if (drv->motor_on)
        {
            if (drv->write_ready)
            {
                disk_pravetz_writebyte(oric, w_byte);
                drv->write_ready = 0;
            }
        }
    }
}

static void  disk_pravetz_switch (struct machine *oric, Uint16  addr)
{
    struct pravetz_drive *drv = &oric->pravetz.drv[oric->wddisk.c_drive];

    switch (addr & 0xF)
    {
    case 0x08:
        drv->motor_on = 0;
        disk_pravetz_write_image(drv);
        break;

    case 0x09:
        drv->motor_on = 0x20;
        break;

    /* select drive 0/1 */
    case 0x0A:
    case 0x0B:
        if (oric->wddisk.c_drive != (addr&1))
        {
            disk_pravetz_write_image(drv);
            oric->wddisk.c_drive = addr&1;
        }
        break;

    case 0x0C:
        drv->select &= 0xFE;
        break;

    case 0x0D:
        drv->select |= 0x01;
        break;

    case 0x0E:
        drv->select &= 0xFD;
        break;

    case 0x0F:
        drv->select |= 0x02;
        break;

    default:
    {
        int phase = (addr & 0x06) >> 1;

        /* move the head in and out by stepping motor */
        if (addr & 0x01)
        {
            phase += 4;
            phase -= (drv->half_track % 4);
            phase %= 4;

            if (1 == phase)
            {
                if (drv->half_track < (2 * PRAV_TRACKS_PER_DISK - 2))
                {
                    drv->half_track++;
                }
            }
            else if (3 == phase)
            {
                if (drv->half_track > 0)
                {
                    drv->half_track--;
                }
            }
        }
    }
    break;
    }
}