504 lines
11 KiB
Java
504 lines
11 KiB
Java
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/**
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* AppleIIGo
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* Disk II Emulator
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* (C) 2006 by Marc S. Ressl(ressl@lonetree.com)
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* Released under the GPL
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* Based on work by Doug Kwan
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*/
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import java.io.*;
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public class DiskII extends Peripheral {
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// ROM (with boot wait cycle optimization)
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private static final int[] rom = {
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0xA2,0x20,0xA0,0x00,0xA2,0x03,0x86,0x3C,0x8A,0x0A,0x24,0x3C,0xF0,0x10,0x05,0x3C,
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0x49,0xFF,0x29,0x7E,0xB0,0x08,0x4A,0xD0,0xFB,0x98,0x9D,0x56,0x03,0xC8,0xE8,0x10,
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0xE5,0x20,0x58,0xFF,0xBA,0xBD,0x00,0x01,0x0A,0x0A,0x0A,0x0A,0x85,0x2B,0xAA,0xBD,
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0x8E,0xC0,0xBD,0x8C,0xC0,0xBD,0x8A,0xC0,0xBD,0x89,0xC0,0xA0,0x50,0xBD,0x80,0xC0,
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0x98,0x29,0x03,0x0A,0x05,0x2B,0xAA,0xBD,0x81,0xC0,0xA9,0x56,0xa9,0x00,0xea,0x88,
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0x10,0xEB,0x85,0x26,0x85,0x3D,0x85,0x41,0xA9,0x08,0x85,0x27,0x18,0x08,0xBD,0x8C,
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0xC0,0x10,0xFB,0x49,0xD5,0xD0,0xF7,0xBD,0x8C,0xC0,0x10,0xFB,0xC9,0xAA,0xD0,0xF3,
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0xEA,0xBD,0x8C,0xC0,0x10,0xFB,0xC9,0x96,0xF0,0x09,0x28,0x90,0xDF,0x49,0xAD,0xF0,
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0x25,0xD0,0xD9,0xA0,0x03,0x85,0x40,0xBD,0x8C,0xC0,0x10,0xFB,0x2A,0x85,0x3C,0xBD,
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0x8C,0xC0,0x10,0xFB,0x25,0x3C,0x88,0xD0,0xEC,0x28,0xC5,0x3D,0xD0,0xBE,0xA5,0x40,
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0xC5,0x41,0xD0,0xB8,0xB0,0xB7,0xA0,0x56,0x84,0x3C,0xBC,0x8C,0xC0,0x10,0xFB,0x59,
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0xD6,0x02,0xA4,0x3C,0x88,0x99,0x00,0x03,0xD0,0xEE,0x84,0x3C,0xBC,0x8C,0xC0,0x10,
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0xFB,0x59,0xD6,0x02,0xA4,0x3C,0x91,0x26,0xC8,0xD0,0xEF,0xBC,0x8C,0xC0,0x10,0xFB,
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0x59,0xD6,0x02,0xD0,0x87,0xA0,0x00,0xA2,0x56,0xCA,0x30,0xFB,0xB1,0x26,0x5E,0x00,
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0x03,0x2A,0x5E,0x00,0x03,0x2A,0x91,0x26,0xC8,0xD0,0xEE,0xE6,0x27,0xE6,0x3D,0xA5,
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0x3D,0xCD,0x00,0x08,0xA6,0x2B,0x90,0xDB,0x4C,0x01,0x08,0x00,0x00,0x00,0x00,0x00,
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};
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// Constants
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private static final int NUM_DRIVES = 2;
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private static final int DOS_NUM_SECTORS = 16;
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private static final int DOS_NUM_TRACKS = 35;
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private static final int DOS_TRACK_BYTES = 256 * DOS_NUM_SECTORS;
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private static final int RAW_TRACK_BYTES = 6250;
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// Disk II direct access variables
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private int drive = 0;
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private boolean isMotorOn = false;
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private byte[][][] disk = new byte[NUM_DRIVES][DOS_NUM_TRACKS][];
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private boolean[] isWriteProtected = new boolean[NUM_DRIVES];
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private int currPhysTrack;
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private int currNibble;
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// Caches
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private int[] driveCurrPhysTrack = new int[NUM_DRIVES];
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private byte[] realTrack;
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/*
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* Disk II emulation:
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*
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* C0xD, C0xE -> Read write protect
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* C0xE, C0xC -> Read data from disk
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* Write data to disk -> C0xF, C0xC
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* Write data to disk -> C0xD, C0xC
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*
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* We use 'fast mode', i.e. no 65(C)02 clock reference
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* We use simplified track handling (only adjacent phases)
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*/
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// Internal registers
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private int latchAddress;
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private int latchData;
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private boolean writeMode;
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// GCR encoding and decoding tables
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private static final int[] gcrEncodingTable = {
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0x96, 0x97, 0x9A, 0x9B, 0x9D, 0x9E, 0x9F, 0xA6,
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0xA7, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF, 0xB2, 0xB3,
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0xB4, 0xB5, 0xB6, 0xB7, 0xB9, 0xBA, 0xBB, 0xBC,
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0xBD, 0xBE, 0xBF, 0xCB, 0xCD, 0xCE, 0xCF, 0xD3,
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0xD6, 0xD7, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE,
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0xDF, 0xE5, 0xE6, 0xE7, 0xE9, 0xEA, 0xEB, 0xEC,
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0xED, 0xEE, 0xEF, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6,
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0xF7, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF,
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};
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private int[] gcrDecodingTable = new int[256];
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private int[] gcrSwapBit = {0, 2, 1, 3};
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private int[] gcrBuffer = new int[256];
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private int[] gcrBuffer2 = new int[86];
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// Physical sector to DOS 3.3 logical sector table
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private static final int[] gcrLogicalSector = {
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0x0, 0x7, 0xE, 0x6, 0xD, 0x5, 0xC, 0x4,
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0xB, 0x3, 0xA, 0x2, 0x9, 0x1, 0x8, 0xF };
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// Temporary variables for conversion
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private byte[] gcrNibbles = new byte[RAW_TRACK_BYTES];
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private int gcrNibblesPos;
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/**
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* Constructor
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*/
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public DiskII() {
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super();
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readDisk(0, null, 254, false);
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readDisk(1, null, 254, false);
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}
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/**
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* I/O read
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*
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* @param address Address
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*/
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public int ioRead(int address) {
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int phase;
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switch (address & 0xf) {
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case 0x0:
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case 0x2:
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case 0x4:
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case 0x6:
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// Q0, Q1, Q2, Q3 off
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break;
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case 0x1:
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// Q0 on
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phase = currPhysTrack & 3;
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if (phase == 1) {
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if (currPhysTrack > 0)
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currPhysTrack--;
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} else if (phase == 3) {
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if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
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currPhysTrack++;
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}
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realTrack = disk[drive][currPhysTrack >> 1];
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break;
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case 0x3:
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// Q1 on
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phase = currPhysTrack & 3;
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if (phase == 2) {
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if (currPhysTrack > 0)
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currPhysTrack--;
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} else if (phase == 0) {
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if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
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currPhysTrack++;
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}
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realTrack = disk[drive][currPhysTrack >> 1];
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break;
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case 0x5:
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// Q2 on
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phase = currPhysTrack & 3;
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if (phase == 3) {
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if (currPhysTrack > 0)
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currPhysTrack--;
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} else if (phase == 1) {
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if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
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currPhysTrack++;
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}
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realTrack = disk[drive][currPhysTrack >> 1];
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break;
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case 0x7:
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// Q3 on
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phase = currPhysTrack & 3;
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if (phase == 0) {
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if (currPhysTrack > 0)
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currPhysTrack--;
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} else if (phase == 2) {
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if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
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currPhysTrack++;
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}
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realTrack = disk[drive][currPhysTrack >> 1];
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break;
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case 0x8:
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// Motor off
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isMotorOn = false;
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break;
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case 0x9:
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// Motor on
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isMotorOn = true;
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break;
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case 0xa:
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// Drive 1
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driveCurrPhysTrack[drive] = currPhysTrack;
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drive = 0;
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currPhysTrack = driveCurrPhysTrack[drive];
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realTrack = disk[drive][currPhysTrack >> 1];
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break;
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case 0xb:
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// Drive 2
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driveCurrPhysTrack[drive] = currPhysTrack;
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drive = 1;
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currPhysTrack = driveCurrPhysTrack[drive];
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realTrack = disk[drive][currPhysTrack >> 1];
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break;
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case 0xc:
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return ioLatchC();
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case 0xd:
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ioLatchD(0xff);
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break;
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case 0xe:
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return ioLatchE();
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case 0xf:
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ioLatchF(0xff);
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break;
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}
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return rand.nextInt(256);
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}
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/**
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* I/O write
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*
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* @param address Address
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*/
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public void ioWrite(int address, int value) {
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switch (address & 0xf) {
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case 0x0:
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case 0x1:
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case 0x2:
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case 0x3:
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case 0x4:
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case 0x5:
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case 0x6:
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case 0x7:
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case 0x8:
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case 0x9:
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case 0xa:
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case 0xb:
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ioRead(address);
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break;
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case 0xc:
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ioLatchC();
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break;
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case 0xd:
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ioLatchD(value);
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break;
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case 0xe:
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ioLatchE();
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break;
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case 0xf:
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ioLatchF(value);
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break;
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}
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}
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/**
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* Memory read
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*
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* @param address Address
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*/
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public int memoryRead(int address) {
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return rom[address & 0xff];
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}
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/**
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* Reset peripheral
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*/
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public void reset() {
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ioRead(0x8);
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}
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/**
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* Loads a disk
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*
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* @param is InputStream
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* @param drive Disk II drive
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*/
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public boolean readDisk(int drive, InputStream is, int volume, boolean isWriteProtected) {
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byte[] track = new byte[RAW_TRACK_BYTES];
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try {
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for (int trackNum = 0; trackNum < DOS_NUM_TRACKS; trackNum++) {
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disk[drive][trackNum] = new byte[RAW_TRACK_BYTES];
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if (is != null) {
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is.read(track, 0, DOS_TRACK_BYTES);
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trackToNibbles(track, disk[drive][trackNum], volume, trackNum);
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}
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}
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this.realTrack = disk[drive][currPhysTrack >> 1];
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this.isWriteProtected[drive] = isWriteProtected;
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return true;
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} catch (IOException e) {
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}
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return false;
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}
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/**
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* Writes a disk
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*
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* @param is InputStream
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* @param drive Disk II drive
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*/
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public boolean writeDisk(int drive, OutputStream os) {
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return true;
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}
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/**
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* Motor on indicator
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*/
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public boolean isMotorOn() {
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return isMotorOn;
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}
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/**
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* I/O read Latch C
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*
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* @param address Address
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*/
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private int ioLatchC() {
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if (writeMode)
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// Write data: C0xD, C0xC
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realTrack[currNibble] = (byte) latchData;
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else
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// Read data: C0xE, C0xC
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latchData = (realTrack[currNibble] & 0xff);
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currNibble++;
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if (currNibble >= RAW_TRACK_BYTES)
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currNibble = 0;
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latchAddress = 0xc;
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return latchData;
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}
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/**
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* I/O write Latch D
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*
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* @param address Address
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*/
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private void ioLatchD(int value) {
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// Prepare write
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writeMode = true;
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latchData = value;
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latchAddress = 0xd;
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}
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/**
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* I/O read Latch E
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*
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* @param address Address
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*/
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private int ioLatchE() {
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// Read write-protect: C0xD, C0xE
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if (latchAddress == 0xd) {
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latchAddress = 0xe;
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return isWriteProtected[drive] ? 0x80 : 0x00;
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}
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writeMode = false;
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latchAddress = 0xe;
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return 0x3c;
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}
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/**
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* I/O write Latch F
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*
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* @param address Address
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*/
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private void ioLatchF(int value) {
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// Prepare write
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writeMode = true;
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latchData = value;
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latchAddress = 0xf;
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}
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/**
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* TRACK CONVERSION ROUTINES
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*/
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/**
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* Writes a nibble
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*
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* @param value Value
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*/
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private final void gcrWriteNibble(int value) {
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gcrNibbles[gcrNibblesPos] = (byte) value;
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gcrNibblesPos++;
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}
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/**
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* Writes sync bits
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*
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* @param length Number of bits
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*/
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private final void writeSync(int length) {
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while(length > 0) {
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length--;
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gcrWriteNibble(0xff);
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}
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}
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/**
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* Write an FM encoded value, used in writing address fields
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*
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* @param value Value
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*/
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private final void encode44(int value) {
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gcrWriteNibble((value >> 1) | 0xaa);
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gcrWriteNibble(value | 0xaa);
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}
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/**
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* Encode in 6:2
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*
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* @param track Sectorized track data
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* @param offset Offset in this data
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*/
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private void encode62(byte[] track, int offset) {
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// 86 * 3 = 258, so the first two byte are encoded twice
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gcrBuffer2[0] = gcrSwapBit[track[offset + 1] & 0x03];
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gcrBuffer2[1] = gcrSwapBit[track[offset] & 0x03];
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// Save higher 6 bits in gcrBuffer and lower 2 bits in gcrBuffer2
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for(int i = 255, j = 2; i >= 0; i--, j = j == 85 ? 0: j + 1) {
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gcrBuffer2[j] = ((gcrBuffer2[j] << 2) | gcrSwapBit[track[offset + i] & 0x03]);
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gcrBuffer[i] = (track[offset + i] & 0xff) >> 2;
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}
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// Clear off higher 2 bits of GCR_buffer2 set in the last call
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for(int i = 0; i < 86; i++)
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gcrBuffer2[i] &= 0x3f;
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}
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/**
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* Write address field
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*
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* @param track Sectorized track data
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* @param offset Offset in this data
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*/
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private final void writeAddressField(int volumeNum, int trackNum, int sectorNum) {
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// Write address mark
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gcrWriteNibble(0xd5);
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gcrWriteNibble(0xaa);
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gcrWriteNibble(0x96);
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// Write volume, trackNum, sector & checksum
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encode44(volumeNum);
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encode44(trackNum);
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encode44(sectorNum);
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encode44(volumeNum ^ trackNum ^ sectorNum);
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// Write epilogue
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gcrWriteNibble(0xde);
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gcrWriteNibble(0xaa);
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gcrWriteNibble(0xeb);
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}
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/**
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* Write data field
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*/
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private void writeDataField() {
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int last = 0;
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int checksum;
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// Write prologue
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gcrWriteNibble(0xd5);
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gcrWriteNibble(0xaa);
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gcrWriteNibble(0xad);
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// Write GCR encoded data
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for(int i = 0x55; i >= 0; i--) {
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checksum = last ^ gcrBuffer2[i];
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gcrWriteNibble(gcrEncodingTable[checksum]);
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last = gcrBuffer2[i];
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}
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for(int i = 0; i < 256; i++) {
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checksum = last ^ gcrBuffer[i];
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gcrWriteNibble(gcrEncodingTable[checksum]);
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last = gcrBuffer[i];
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}
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// Write checksum
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gcrWriteNibble(gcrEncodingTable[last]);
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// Write epilogue
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gcrWriteNibble(0xde);
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gcrWriteNibble(0xaa);
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gcrWriteNibble(0xeb);
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}
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/**
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* Converts a track to nibbles
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*/
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private void trackToNibbles(byte[] track, byte[] nibbles, int volumeNum, int trackNum) {
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this.gcrNibbles = nibbles;
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gcrNibblesPos = 0;
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for (int sectorNum = 0; sectorNum < DOS_NUM_SECTORS; sectorNum++) {
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encode62(track, gcrLogicalSector[sectorNum] << 8);
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writeSync(12);
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writeAddressField(volumeNum, trackNum, sectorNum);
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writeSync(8);
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writeDataField();
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}
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writeSync(RAW_TRACK_BYTES - gcrNibblesPos);
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}
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}
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