Version 1.0.10 - changes by Nick

- fixed disk stepping bug for Mabel's Mansion using my code from AppleWin - patch loaded ROM's empty slots with faux-floating bus data so Mabel's Mansion works - revert CPU status bug introduced in 1.0.9 - V and R used the same bit - fixed BRK bug by adding extra PC increment
Update README.md
2015-08-10 00:11:49 +12:00 · 2015-08-01 20:25:49 +12:00 · 2015-08-01 20:09:35 +12:00
9 changed files with 164 additions and 105 deletions
--- a/README.md
+++ b/README.md
@ -1,6 +1,10 @@
 # AppleIIGo
 Apple //e emulator Java applet

-Original version: Copyright 2006 Marc S. Ressl
+Original version: Copyright 2006 Marc S. Ressl, with parts adapted from code by
+- Steven E. Hugg
+- Doug Kwan
+- Randy Frank
+- Ben Koning

 Subsequent versions: Copyright 2008-2015 Nick Westgate
--- a/Source/AppleDisplay.java
+++ b/Source/AppleDisplay.java
@ -2,7 +2,7 @@
 /**
 * AppleIIGo
 * Display processing
- * (C) 2006 by Marc S. Ressl (mressl@gmail.com)
+ * Copyright 2006 by Marc S. Ressl (mressl@gmail.com)
 * Released under the GPL
 */

--- a/Source/AppleIIGo.java
+++ b/Source/AppleIIGo.java
@ -2,13 +2,25 @@
 /**
 * AppleIIGo
 * The Java Apple II Emulator 
- * Copyright 2011 by Nick Westgate (Nick.Westgate@gmail.com)
+ * Copyright 2015 by Nick Westgate (Nick.Westgate@gmail.com)
 * Copyright 2006 by Marc S. Ressl (mressl@gmail.com)
 * Released under the GNU General Public License version 2 
 * See http://www.gnu.org/licenses/
 * 
 * Change list:
 * 
+ * Version 1.0.10 - changes by Nick:
+ * - fixed disk stepping bug for Mabel's Mansion using my code from AppleWin
+ * - patch loaded ROM's empty slots with faux-floating bus data so Mabel's Mansion works
+ * - revert CPU status bug introduced in 1.0.9 - V and R used the same bit
+ * - fixed BRK bug by adding extra PC increment
+ * - NOTE: decimal mode arithmetic fails some tests and should be fixed someday
+ * 
+ * Version 1.0.9 - changes by Nick:
+ * - fixed disk speed-up bug (Sherwood Forest reads with the drive motor off)
+ * - added check for 2IMG header ID
+ * - fixed processor status bugs in BRK, PLP, RTI, NMI, IRQ 
+ * 
 * Version 1.0.8 - changes by Nick:
 * - implemented disk writing (only in memory, not persisted)
 * - added support for .2MG (2IMG) disk images, including lock flag and volume number
@ -80,7 +92,7 @@ public class AppleIIGo extends Applet implements KeyListener, ComponentListener,

 	private static final long serialVersionUID = -3302282815441501352L;
 	
-	final String version = "1.0.8";
+	final String version = "1.0.10";
 	final String versionString = "AppleIIGo Version " + version;
 	final String metaStart = "_meta_";

--- a/Source/AppleSpeaker.java
+++ b/Source/AppleSpeaker.java
@ -2,7 +2,7 @@
 /**
 * AppleIIGo
 * Speaker processing
- * (C) 2006 by Marc S. Ressl(mressl@gmail.com)
+ * Copyright 2006 by Marc S. Ressl(mressl@gmail.com)
 * Released under the GPL
 */

--- a/Source/DiskII.java
+++ b/Source/DiskII.java
@ -2,8 +2,8 @@
 /**
 * AppleIIGo
 * Disk II Emulator
- * (C) 2006 by Marc S. Ressl(mressl@gmail.com)
- * (C) 2011 by Nick Westgate (Nick.Westgate@gmail.com)
+ * Copyright 2015 by Nick Westgate (Nick.Westgate@gmail.com)
+ * Copyright 2006 by Marc S. Ressl(mressl@gmail.com)
 * Released under the GPL
 * Based on work by Doug Kwan
 */
@ -36,13 +36,16 @@ public class DiskII extends Peripheral {
 	private static final int NUM_DRIVES = 2;
 	private static final int DOS_NUM_SECTORS = 16;
 	private static final int DOS_NUM_TRACKS = 35;
+	private static final int MAX_PHYS_TRACK = (2 * DOS_NUM_TRACKS) - 1;
 	private static final int DOS_TRACK_BYTES = 256 * DOS_NUM_SECTORS;
 	private static final int RAW_TRACK_BYTES = 0x1A00; // 0x1A00 (6656) for .NIB (was 6250)
+	private static final int STANDARD_2IMG_HEADER_ID = 0x32494D47;
 	private static final int STANDARD_2IMG_HEADER_SIZE = 64;
 	private static final int STANDARD_PRODOS_BLOCKS = 280;
 	
 	// Disk II direct access variables
 	private int drive = 0;
+	private int phases = 0;
 	private boolean isMotorOn = false;

 	private byte[][][] diskData = new byte[NUM_DRIVES][DOS_NUM_TRACKS][];
@ -71,7 +74,7 @@ public class DiskII extends Peripheral {
 	private int latchData;
 	private boolean writeMode;
 	private boolean loadMode;
-	private boolean driveSpin;
+	private int driveSpin;
 	
 	// GCR encoding and decoding tables
 	private static final int[] gcrEncodingTable = {
@ -168,20 +171,8 @@ public class DiskII extends Peripheral {
 				break;
 		}
 		
-        if ((address & 1) == 0)
-        {
-        	// only even addresses return the latch
-        	if (isMotorOn)
-        	{
-        		return latchData;
-        	}
-
-        	// simple hack to fool DOS SAMESLOT drive spin check (usually at $BD34)
-        	driveSpin = !driveSpin;
-        	return driveSpin ? 0x7E : 0x7F;
-        }
-
-		return rand.nextInt(256); // TODO: floating bus
+		// only even addresses return the latch
+		return ((address & 1) == 0) ? latchData : rand.nextInt(256); // TODO: floating bus
    }
 	
 	/**
@ -247,7 +238,10 @@ public class DiskII extends Peripheral {
 	 * Reset peripheral
 	 */
 	public void reset() {
-		ioRead(0x8);
+		drive = 0;
+		isMotorOn = false;
+		loadMode = false;
+		writeMode = false;
 	}

 	/**
@ -266,6 +260,10 @@ public class DiskII extends Peripheral {
 				byte[] header = new byte[STANDARD_2IMG_HEADER_SIZE];
 				is.readFully(header, 0, STANDARD_2IMG_HEADER_SIZE);

+				int id = (header[0x00] << 24) | (header[0x01] << 16) | (header[0x02] << 8) | (header[0x03]);
+				if (id != STANDARD_2IMG_HEADER_ID)
+					return false;
+
 				int headerSize = (header[0x09] << 8) | (header[0x08]);
 				if (headerSize != STANDARD_2IMG_HEADER_SIZE)
 					return false;
@ -352,17 +350,29 @@ public class DiskII extends Peripheral {
 		loadMode = false;
 		if (!writeMode)
 		{
+			if (!isMotorOn)
+			{
+				// simple hack to fool RWTS SAMESLOT drive spin check (usually at $BD34)
+				driveSpin = (driveSpin + 1) & 0xF;
+				if (driveSpin == 0)
+				{
+					latchData = 0x7F;
+					return;
+				}
+			}
+
 			// Read data: C0xE, C0xC
 			latchData = (realTrack[currNibble] & 0xff);

-			// simple hack to help DOS find address prologues ($B94F)
+			// is RWTS looking for an address prologue? (RDADR)
 			if (/* fastDisk && */ // TODO: fastDisk property to enable/disable 
 				apple.memoryRead(apple.PC + 3) == 0xD5 && // #$D5
-				apple.memoryRead(apple.PC + 2) == 0xC9 && // CMP
+				apple.memoryRead(apple.PC + 2) == 0xC9 && // CMP (usually at $B94F)
 				apple.memoryRead(apple.PC + 1) == 0xFB && // PC - 3
 				apple.memoryRead(apple.PC + 0) == 0x10 &&  // BPL
 				latchData != 0xD5) 
 			{
+				// Y: find the next address prologues
 				int count = RAW_TRACK_BYTES / 16;
 				do
 				{
@ -373,8 +383,8 @@ public class DiskII extends Peripheral {
 				}
 				while (latchData != 0xD5 && --count > 0);
 			}
-			// skip invalid nibbles we padded the track buffer with 
-			else if (latchData == 0x7F) // TODO: maybe the above covers this?
+			// N: skip invalid nibbles we padded the track buffer with 
+			else if (latchData == 0x7F)
 			{
 				int count = RAW_TRACK_BYTES / 16;
 				do
@ -399,68 +409,42 @@ public class DiskII extends Peripheral {
 	}

 	private void setPhase(int address) {
-		int phase;
-		
-		switch (address & 0xf) {
-			case 0x0:
-			case 0x2:			
-			case 0x4:
-			case 0x6:
-				// Q0, Q1, Q2, Q3 off
-				break;
-			case 0x1:
-				// Q0 on
-				phase = currPhysTrack & 3;
-				if (phase == 1) {
-					if (currPhysTrack > 0)
-						currPhysTrack--;
-				} else if (phase == 3) {
-					if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
-						currPhysTrack++;
-				}
-				//System.out.println("half track=" + currPhysTrack);
-				realTrack = diskData[drive][currPhysTrack >> 1];
-				break;
-			case 0x3:
-				// Q1 on
-				phase = currPhysTrack & 3;
-				if (phase == 2) {
-					if (currPhysTrack > 0)
-						currPhysTrack--;
-				} else if (phase == 0) {
-					if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
-						currPhysTrack++;
-				}
-				//System.out.println("half track=" + currPhysTrack);
-				realTrack = diskData[drive][currPhysTrack >> 1];
-				break;
-			case 0x5:
-				// Q2 on
-				phase = currPhysTrack & 3;
-				if (phase == 3) {
-					if (currPhysTrack > 0)
-						currPhysTrack--;
-				} else if (phase == 1) {
-					if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
-						currPhysTrack++;
-				}
-				//System.out.println("half track=" + currPhysTrack);
-				realTrack = diskData[drive][currPhysTrack >> 1];
-				break;
-			case 0x7:
-				// Q3 on
-				phase = currPhysTrack & 3;
-				if (phase == 0) {
-					if (currPhysTrack > 0)
-						currPhysTrack--;
-				} else if (phase == 2) {
-					if (currPhysTrack < ((2 * DOS_NUM_TRACKS) - 1))
-						currPhysTrack++;
-				}
-				//System.out.println("half track=" + currPhysTrack);
-				realTrack = diskData[drive][currPhysTrack >> 1];
-				break;
+		int phase = (address >> 1) & 3;
+		int phase_bit = (1 << phase);
+
+		// update the magnet states
+		if ((address & 1) != 0)
+		{
+			// phase on
+			phases |= phase_bit;
 		}
+		else
+		{
+			// phase off
+			phases &= ~phase_bit;
+		}
+
+		// check for any stepping effect from a magnet
+		// - move only when the magnet opposite the cog is off
+		// - move in the direction of an adjacent magnet if one is on
+		// - do not move if both adjacent magnets are on
+		// momentum and timing are not accounted for ... maybe one day!
+		int direction = 0;
+		if ((phases & (1 << ((currPhysTrack + 1) & 3))) != 0)
+			direction += 1;
+		if ((phases & (1 << ((currPhysTrack + 3) & 3))) != 0)
+			direction -= 1;
+
+		// apply magnet step, if any
+		if (direction != 0)
+		{
+			currPhysTrack += direction;
+			if (currPhysTrack < 0)
+				currPhysTrack = 0;
+			else if (currPhysTrack > MAX_PHYS_TRACK)
+				currPhysTrack = MAX_PHYS_TRACK;
+		}
+		realTrack = diskData[drive][currPhysTrack >> 1];
 	}

 	private void setDrive(int newDrive) {
--- a/Source/Em6502.java
+++ b/Source/Em6502.java
@ -1,12 +1,14 @@
+import java.io.PrintWriter;
+

 /**
 * AppleIIGo
 * Apple II Emulator for J2SE
- * (C) 2006 by Marc S. Ressl(mressl@gmail.com)
+ * Copyright 2006 by Marc S. Ressl(mressl@gmail.com)
 * Released under the GPL
 * Adapted from code by Doug Kwan
 * Adapted from code by Randy Frank randy@tessa.iaf.uiowa.edu
- * Adapted from code (C) 1989 Ben Koning [556498717 408/738-1763 ben@apple.com]
+ * Adapted from code Copyright 1989 Ben Koning [556498717 408/738-1763 ben@apple.com]
 */

 public class Em6502 {
@ -78,6 +80,7 @@ public class Em6502 {
 	public static final int FLAG_I = (1 << 2);
 	public static final int FLAG_D = (1 << 3);
 	public static final int FLAG_B = (1 << 4);
+	public static final int FLAG_R = (1 << 5);
 	public static final int FLAG_V = (1 << 6);
 	public static final int FLAG_N = (1 << 7);
 	/*
@ -120,6 +123,8 @@ public class Em6502 {
 	 * Constructor
 	 */
 	public Em6502() {
+//		createRunFile(); // TODO: for debugging - disable
+		
 		// Init BCD tables
 		BCDTableAdd = new int[512];
 		BCDTableSub = new int[512];
@ -133,6 +138,10 @@ public class Em6502 {
 			BCDTableSub[i] = ((i & 0x0f) <= 0x09) ? i : (i - 0x06);
 			BCDTableSub[i] -= ((BCDTableSub[i] & 0xf0) <= 0x90) ? 0 : 0x60;
 		}
+
+		// Init CPU
+        S = 0xFF;
+		P = FLAG_B | FLAG_R;
 	}
 	
 	/*
@ -154,7 +163,7 @@ public class Em6502 {
 	 */
 	private final void setN(boolean b) {if (b) P |= FLAG_N; else P &= ~FLAG_N;}
 	private final void setV(boolean b) {if (b) P |= FLAG_V; else P &= ~FLAG_V;}
-	private final void setB(boolean b) {if (b) P |= FLAG_B; else P &= ~FLAG_B;}
+//	private final void setB(boolean b) {if (b) P |= FLAG_B; else P &= ~FLAG_B;}
 	private final void setD(boolean b) {if (b) P |= FLAG_D; else P &= ~FLAG_D;}
 	private final void setI(boolean b) {if (b) P |= FLAG_I; else P &= ~FLAG_I;}
 	private final void setZ(boolean b) {if (b) P |= FLAG_Z; else P &= ~FLAG_Z;}
@ -294,9 +303,48 @@ public class Em6502 {
 		clock++;
 	}

+//	private PrintWriter runFile;
+//	private boolean runFlag = false;
+//
+//	private void createRunFile()
+//	{
+//		try
+//		{
+//			//runFile = new PrintWriter("C:\\Dev\\Emulators\\AppleIIGo\\AppleIIGoRun.txt");
+//		}
+//		catch (Exception ex)
+//		{
+//			// swallow
+//		}
+//	}
+//
+//	private final void writeRunFile(int opcode)
+//	{
+//		if (PC == 0x2000)
+//			runFlag = true;
+//		if (
+//				runFlag &&
+//				(PC > 0x1000)
+//				&&
+//				(PC < 0xC000)
+//			)
+//		{
+//			if (runFile != null)
+//			{
+//				setN(getFN());
+//				setZ(getFZ());
+//				setC(getFC());
+//
+//				runFile.printf("%04X-%02X P=%02X A=%02X\r\n", PC, opcode, P, A);
+//				runFile.flush();
+//			}
+//		}
+//	}
+	
 	/** This executes a single instruction. */
 	private final void executeInstruction() {
 		opcode = memoryRead(PC);
+//		writeRunFile(opcode); // TODO: for debugging = disable
 		PC++;
 		
 		switch(opcode) {
@ -530,13 +578,13 @@ public class Em6502 {
 			break;
 			
 		case 0x00:	// BRK
+			PC++;
 			push(PC >> 8);	// save PCH, PCL & P
 			push(PC);
 			setN(getFN());
 			setZ(getFZ());
 			setC(getFC());
-			setB(true);
-			push(P);
+			push(P); // B and R always set
 			setI(true);
 			PC = memoryRead(0xfffe);
 			PC |= memoryRead(0xffff) << 8;
@ -1043,7 +1091,7 @@ public class Em6502 {
 			break;
 			
 		case 0x28:	// PLP
-			P = pop() | 0x20; // fix bug in bit5 of P
+			P = pop() | FLAG_B | FLAG_R; // B and R always set
 			setFC(getC());
 			setFNZ(getN(), getZ());
 			clock += 4;
@ -1144,7 +1192,7 @@ public class Em6502 {
 			break;
 			
 		case 0x40:	// RTI
-			P = pop() | 0x20; // bit 5 bug of 6502
+			P = pop() | FLAG_B | FLAG_R; // B and R always set
 			setFC(getC());
 			setFNZ(getN(), getZ());
 			PC = pop();	// splitting is necessary
@ -1570,13 +1618,13 @@ public class Em6502 {
 		if ((exceptionRegister & SIG_6502_RESET) != 0) {
 			onReset();
 			
-			PC = memoryRead(0xfffc);
-			PC |= (memoryRead(0xfffd) << 8);
-			S = (S - 3) & 0xff;
-			setI(true);
 			setD(false); // not on NMOS 6502
 			setFC(getC());
 			setFNZ(getN(), getZ());
+			S = (S - 3) & 0xff;
+			setI(true);
+			PC = memoryRead(0xfffc);
+			PC |= (memoryRead(0xfffd) << 8);
 			clock += 7;
 			exceptionRegister &= ~SIG_6502_RESET;
 		}
@ -1590,7 +1638,8 @@ public class Em6502 {
 			setN(getFN());
 			setZ(getFZ());
 			setC(getFC());
-			push(P);
+			push(P & ~FLAG_B);
+			setI(true);
 			PC = memoryRead(0xfffa);
 			PC |= memoryRead(0xfffb) << 8;
 			clock += 7;
@ -1608,8 +1657,7 @@ public class Em6502 {
 				setN(getFN());
 				setZ(getFZ());
 				setC(getFC());
-				setB(false);
-				push(P);
+				push(P & ~FLAG_B);
 				setI(true);
 				PC = memoryRead(0xfffe);
 				PC |= memoryRead(0xffff) << 8;
--- a/Source/EmAppleII.java
+++ b/Source/EmAppleII.java
@ -2,7 +2,7 @@
 /**
 * AppleIIGo
 * Apple II Emulator for J2ME
- * (C) 2006 by Marc S. Ressl(mressl@gmail.com)
+ * Copyright 2006 by Marc S. Ressl(mressl@gmail.com)
 * Released under the GPL
 */

@ -264,6 +264,17 @@ public class EmAppleII extends Em6502 implements Runnable {
 		System.arraycopy(rom, offset + 0x3000, mem, MEM_ROM_INTERNAL + 0x00000, 0x01000);
 		System.arraycopy(rom, offset + 0x3800, mem, MEM_ROM_EXTERNAL + 0x00800, 0x00800);

+		for (int slot = 0x100; slot <= 0x700; slot += 0x100)
+		{
+			if (mem[MEM_ROM_EXTERNAL + slot] == 0)
+			{
+				// 0 data is a bad default for empty external slots (e.g. Mabel's Mansion reboots)
+				// so ideally we would emulate the floating bus, but for now we just hardcode 0xA0
+				for (int i = 0; i <= 0xFF; i++)
+					mem[MEM_ROM_EXTERNAL + slot + i] = (byte)0xA0;
+			}
+		}
+
 		return true;
 	}

--- a/Source/Paddle.java
+++ b/Source/Paddle.java
@ -2,7 +2,7 @@
 /**
 * AppleIIGo
 * Apple II Emulator for J2ME
- * (C) 2006 by Marc S. Ressl(mressl@gmail.com)
+ * Copyright 2006 by Marc S. Ressl(mressl@gmail.com)
 * Released under the GPL
 */

--- a/Source/Peripheral.java
+++ b/Source/Peripheral.java
@ -2,7 +2,7 @@
 /**
 * AppleIIGo
 * Slot interface
- * (C) 2006 by Marc S. Ressl(mressl@gmail.com)
+ * Copyright 2006 by Marc S. Ressl(mressl@gmail.com)
 * Released under the GPL
 * Based on work by Steven E. Hugg
 */