src/floppy.js

"use strict";

/** @constructor */
function FloppyController(cpu, fda_image, fdb_image)
{

    this.io = cpu.io;
    this.pic = cpu.devices.pic;
    this.dma = cpu.devices.dma;

    this.bytes_expecting = 0;
    this.receiving_command = new Uint8Array(10);
    this.receiving_index = 0;
    this.next_command = null;

    this.response_data = new Uint8Array(10);
    this.response_index = 0;
    this.response_length = 0;

    this.floppy_size = 0;

    this.buffer = fda_image;
    this.fda_image = fda_image;
    this.fdb_image = fdb_image;

    this.status_reg0 = 0;
    this.status_reg1 = 0;
    this.status_reg2 = 0;
    this.drive = 0;

    this.last_cylinder = 0;
    this.last_head = 0;
    this.last_sector = 1;

    if(!fda_image)
    {
        this.type = 4;
        return;
    }

    this.floppy_size = fda_image.byteLength;

    var floppy_types = {
        160  : { type: 1, tracks: 40, sectors: 8 , heads: 1 },
        180  : { type: 1, tracks: 40, sectors: 9 , heads: 1 },
        200  : { type: 1, tracks: 40, sectors: 10, heads: 1 },
        320  : { type: 1, tracks: 40, sectors: 8 , heads: 2 },
        360  : { type: 1, tracks: 40, sectors: 9 , heads: 2 },
        400  : { type: 1, tracks: 40, sectors: 10, heads: 2 },
        720  : { type: 3, tracks: 80, sectors: 9 , heads: 2 },
        1200 : { type: 2, tracks: 80, sectors: 15, heads: 2 },
        1440 : { type: 4, tracks: 80, sectors: 18, heads: 2 },
        1722 : { type: 5, tracks: 82, sectors: 21, heads: 2 },
        2880 : { type: 5, tracks: 80, sectors: 36, heads: 2 },
    };

    var number_of_cylinders,
        sectors_per_track,
        number_of_heads,
        floppy_type = floppy_types[this.floppy_size >> 10];

    if(floppy_type && (this.floppy_size & 0x3FF) === 0)
    {
        this.type = floppy_type.type;

        sectors_per_track = floppy_type.sectors;
        number_of_heads = floppy_type.heads;
        number_of_cylinders = floppy_type.tracks;
    }
    else
    {
        throw "Unknown floppy size: " + h(fda_image.byteLength);
    }

    this.sectors_per_track = sectors_per_track;
    this.number_of_heads = number_of_heads;
    this.number_of_cylinders = number_of_cylinders;

    this.io.register_read(0x3F0, this.port3F0_read, this);
    this.io.register_read(0x3F2, this.port3F2_read, this);
    this.io.register_read(0x3F4, this.port3F4_read, this);
    this.io.register_read(0x3F5, this.port3F5_read, this);
    this.io.register_read(0x3F7, this.port3F7_read, this);

    this.io.register_write(0x3F2, this.port3F2_write, this);
    this.io.register_write(0x3F5, this.port3F5_write, this);

}

FloppyController.prototype.port3F0_read = function()
{
    dbg_log("3F0 read", LOG_DISK);

    return 0;
};


FloppyController.prototype.port3F4_read = function()
{
    dbg_log("3F4 read", LOG_DISK);

    var return_byte = 0x80;

    if(this.response_index < this.response_length)
    {
        return_byte |= 0x40 | 0x10;
    }

    if((dor & 8) === 0)
    {
        return_byte |= 0x20;
    }

    return return_byte;
};

FloppyController.prototype.port3F7_read = function()
{
    dbg_log("3F7 read", LOG_DISK);
    return 0x00;
}

FloppyController.prototype.port3F5_read = function()
{
    if(this.response_index < this.response_length)
    {
        dbg_log("3F5 read: " + this.response_data[this.response_index], LOG_DISK);
        return this.response_data[this.response_index++];
    }
    else
    {
        dbg_log("3F5 read, empty", LOG_DISK);
        return 0xFF;
    }
};

FloppyController.prototype.port3F5_write = function(reg_byte)
{
    dbg_log("3F5 write " + h(reg_byte), LOG_DISK);

    if(this.bytes_expecting > 0)
    {
        this.receiving_command[this.receiving_index++] = reg_byte;

        this.bytes_expecting--;

        if(this.bytes_expecting === 0)
        {
            if(DEBUG)
            {
                var log = "3F5 command received: ";
                for(var i = 0; i < this.receiving_index; i++) 
                    log += h(this.receiving_command[i]) + " ";
                dbg_log(log, LOG_DISK);
            }

            this.next_command.call(this, this.receiving_command);
        }
    }
    else
    {
        switch(reg_byte)
        {
            // TODO
            //case 2:
                //this.next_command = read_complete_track;
                //this.bytes_expecting = 8;
                //break;
            case 0x03:
                this.next_command = this.fix_drive_data;
                this.bytes_expecting = 2;
                break;
            case 0x04:
                this.next_command = this.check_drive_status;
                this.bytes_expecting = 1;
                break;
            case 0x05:
            case 0xC5:
                this.next_command = function(args) { this.do_sector(true, args); };
                this.bytes_expecting = 8;
                break;
            case 0xE6:
                this.next_command = function(args) { this.do_sector(false, args); };
                this.bytes_expecting = 8;
                break;
            case 0x07:
                this.next_command = this.calibrate;
                this.bytes_expecting = 1;
                break;
            case 0x08:
                this.check_interrupt_status();
                break;
            case 0x4A:
                this.next_command = this.read_sector_id;
                this.bytes_expecting = 1;
                break;
            case 0x0F:
                this.bytes_expecting = 2;
                this.next_command = this.seek;
                break;
            case 0x0E:
                // dump regs 
                dbg_log("dump registers", LOG_DISK);
                this.response_data[0] = 0x80;
                this.response_index = 0;
                this.response_length = 1;

                this.bytes_expecting = 0;
                break;
            default:
                if(DEBUG) throw "unimpl floppy command call " + h(reg_byte);
        }

        this.receiving_index = 0;
    }
};


// this should actually be write-only ... but people read it anyway
var dor = 0;

FloppyController.prototype.port3F2_read = function()
{
    dbg_log("read 3F2: DOR", LOG_DISK);
    return dor;
}

FloppyController.prototype.port3F2_write = function(value)
{
    if((value & 4) === 4 && (dor & 4) === 0)
    {
        // reset
        this.pic.push_irq(6);
    }

    dbg_log("start motors: " + h(value >> 4), LOG_DISK);
    dbg_log("enable dma: " + !!(value & 8), LOG_DISK);
    dbg_log("reset fdc: " + !!(value & 4), LOG_DISK);
    dbg_log("drive select: " + (value & 3), LOG_DISK);
    dbg_log("DOR = " + h(value), LOG_DISK);

    dor = value;

}

FloppyController.prototype.check_drive_status = function(args)
{
    dbg_log("check drive status", LOG_DISK);

    this.response_index = 0;
    this.response_length = 1;
    this.response_data[0] = 1 << 5;
}

FloppyController.prototype.seek = function(args)
{
    dbg_log("seek", LOG_DISK);

    this.last_cylinder = args[1];
    this.last_head = args[0] >> 2 & 1;
    
    if(dor & 8)
    {
        this.pic.push_irq(6);
    }
}

FloppyController.prototype.calibrate = function(args)
{
    dbg_log("floppy calibrate", LOG_DISK);

    if(dor & 8)
    {
        this.pic.push_irq(6);
    }
}

FloppyController.prototype.check_interrupt_status = function()
{
    // do not trigger an interrupt here
    dbg_log("floppy check interrupt status", LOG_DISK);

    this.response_index = 0;
    this.response_length = 2;

    this.response_data[0] = 1 << 5;
    this.response_data[1] = this.last_cylinder;
}

FloppyController.prototype.do_sector = function(is_write, args)
{
    var head = args[2],
        cylinder = args[1],
        sector = args[3],
        sector_size = 128 << args[4],
        read_count = args[5] - args[3] + 1,

        read_offset = ((head + this.number_of_heads * cylinder) * this.sectors_per_track + sector - 1) * sector_size;
    
    dbg_log("Floppy Read", LOG_DISK);
    dbg_log("from " + h(read_offset) + " length " + h(read_count * sector_size), LOG_DISK);
    dbg_log(cylinder + " / " + head + " / " + sector, LOG_DISK);

    if(!args[4])
    {
        dbg_log("FDC: sector count is zero, use data length instead", LOG_DISK);
    }

    if(is_write)
    {
        this.dma.do_write(this.fda_image, read_offset, read_count * sector_size, 2, this.done.bind(this, args, cylinder, head, sector));
    }
    else
    {
        this.dma.do_read(this.fda_image, read_offset, read_count * sector_size, 2, this.done.bind(this, args, cylinder, head, sector));
    }
};

FloppyController.prototype.done = function(cylinder, args, head, sector, error)
{
    if(error)
    {
        // TODO: Set appropriate bits
        return;
    }

    sector++;

    if(sector > this.sectors_per_track)
    {
        sector = 1;
        head++;

        if(head >= this.number_of_heads)
        {
            head = 0;
            cylinder++;
        }
    }

    this.last_cylinder = cylinder;
    this.last_head = head;
    this.last_sector = sector;

    this.response_index = 0;
    this.response_length = 7;

    this.response_data[0] = head << 2 | 0x20; 
    this.response_data[1] = 0; 
    this.response_data[2] = 0; 
    this.response_data[3] = cylinder; 
    this.response_data[4] = head; 
    this.response_data[5] = sector; 
    this.response_data[6] = args[4];

    if(dor & 8)
    {
        this.pic.push_irq(6);
    }
}

FloppyController.prototype.fix_drive_data = function(args)
{
    dbg_log("floppy fix drive data " + args, LOG_DISK);
}

FloppyController.prototype.read_sector_id = function(args)
{
    dbg_log("floppy read sector id " + args, LOG_DISK);

    this.response_index = 0;
    this.response_length = 7;

    this.response_data[0] = 0;
    this.response_data[1] = 0;
    this.response_data[2] = 0;
    this.response_data[3] = 0;
    this.response_data[4] = 0;
    this.response_data[5] = 0;
    this.response_data[6] = 0;

    if(dor & 8)
    {
        this.pic.push_irq(6);
    }
}