Initial 65C02 Support

First pass at adding CMOS 65C02 support for the following instructions
and addressing modes:

   * ORA (ZP Indirect)
   * AND (ZP Indirect)
   * EOR (ZP Indirect)
   * ADC (ZP Indirect)
   * STA (ZP Indirect)
   * LDA (ZP Indirect)
   * CMP (ZP Indirect)
   * SBC (ZP Indirect)

README.md

@@ -1,9 +1,9 @@
 SYMON - A 6502 System Simulator
 ===============================
 
-**Version:** 1.1.1
+**Version:** 1.2.1
 
-**Last Updated:** 2 January, 2016
+**Last Updated:** 8 January, 2016
 
 See the file COPYING for license.
 
@@ -188,7 +188,7 @@ Maven will build Symon, run unit tests, and produce a jar file in the
 Symon is meant to be invoked directly from the jar file. To run with
 Java 1.8 or greater, just type:
 
-    $ java -jar symon-1.1.1.jar
+    $ java -jar symon-1.2.0.jar
 
 When Symon is running, you should be presented with a simple graphical
 interface.
@@ -235,6 +235,12 @@ running.
 
 ## 5.0 Revision History
 
+  - **1.2.1:** 8 January, 2016 - Remove dependency on Java 8. Now
+    supports compiling and running under Java 1.7.
+
+  - **1.2.0:** 3 January, 2016 - Add symbolic disassembly to breakpoints
+    window.
+  
   - **1.1.1:** 2 January, 2016 - Minor enhancement: Allows breakpoints
     to be added with the Enter key.
 
@@ -286,7 +292,15 @@ running.
 
   - **0.1:** 20 January, 2010
 
-## 6.0 To Do
+## 6.0 Roadmap
+
+  - **1.2:** Better breakpoint support. Symbolic debugging of breakpoints.
+
+  - **2.0:** Complete rewrite of the UI in JavaFX instead of Swing. Complete
+    assembler and disassembler built in. Ability to attach source code for
+    symbolic debugging.
+
+## 7.0 To Do
 
   - Feedback (in the form of dialogs, status bar, etc).
 
@@ -310,7 +324,7 @@ running.
 
   - Symbolic debugging.
 
-## 7.0 Copyright and Acknowledgements
+## 8.0 Copyright and Acknowledgements
 
 **Copyright (c) 2014 Seth J. Morabito <web@loomcom.com>**
 
@@ -330,7 +344,7 @@ This project would not have been possible without the following resources:
   - [Neil Parker's "The 6502/65C02/65C816 Instruction Set Decoded"] (http://www.llx.com/~nparker/a2/opcodes.html),
     for information about how instructions are coded
 
-## 8.0 Licensing
+## 9.0 Licensing
 
 Symon is free software.  It is distributed under the MIT License.
 Please see the file 'COPYING' for full details of the license.

pom.xml

@@ -4,7 +4,7 @@
     <groupId>com.loomcom.symon</groupId>
     <artifactId>symon</artifactId>
     <packaging>jar</packaging>
-    <version>1.1.1</version>
+    <version>1.3.0-SNAPSHOT</version>
     <name>symon</name>
     <url>http://www.loomcom.com/symon</url>
     <properties>
@@ -91,8 +91,8 @@
                 <version>3.1</version>
                 <configuration>
                     <compilerArgument>-Xlint:unchecked</compilerArgument>
-                    <source>1.8</source>
-                    <target>1.8</target>
+                    <source>1.7</source>
+                    <target>1.7</target>
                 </configuration>
             </plugin>
 

samples/echo_irq/Makefile

@@ -7,7 +7,7 @@ echo_irq: echo_irq.o
 	$(LD) -C symon.config -vm -m echo_irq.map -o echo_irq.rom echo_irq.o
 
 echo_irq.o:
-	$(CA) --listing -o echo_irq.o echo_irq.asm
+	$(CA) --listing echo_irq.lst -o echo_irq.o echo_irq.asm
 
 clean:
 	rm -f *.o *.rom *.map *.lst

samples/echo_irq/symon.config

@@ -1,5 +1,5 @@
 MEMORY {
-RAM1: start = $0000, size = $8000;
+RAM1: start = $0000, size = $8000 - __STACKSIZE__;
 ROM1: start = $C000, size = $3FFA, fill = yes;
 ROMV: start = $FFFA, size = $6, file = %O, fill = yes;
 }
@@ -11,6 +11,6 @@ VECTORS:  load = ROMV, type = ro;
 }
 
 SYMBOLS {
-__STACKSIZE__ = $0300;
+__STACKSIZE__: type = weak, value = $0300;
 }
 

samples/ehbasic/Makefile

@@ -7,7 +7,7 @@ ehbasic: ehbasic.o
 	$(LD) -C symon.config -vm -m ehbasic.map -o ehbasic.rom ehbasic.o
 
 ehbasic.o:
-	$(CA) --listing -o ehbasic.o min_mon.asm
+	$(CA) --listing ehbasic.lst -o ehbasic.o min_mon.asm
 
 clean:
 	rm -f *.o *.rom *.map *.lst

samples/ehbasic/symon.config

@@ -1,5 +1,5 @@
 MEMORY {
-RAM1: start = $0000, size = $8000;
+RAM1: start = $0000, size = $8000 - __STACKSIZE__;
 ROM1: start = $C000, size = $3F00, fill = yes;
 MONITOR: start = $FF00, size = $FA, fill = yes;
 ROMV: start = $FFFA, size = $6, file = %O, fill = yes;
@@ -13,6 +13,6 @@ VECTORS:  load = ROMV, type = ro;
 }
 
 SYMBOLS {
-__STACKSIZE__ = $0300;
+__STACKSIZE__: type = weak, value = $0300;
 }
 

samples/ehbasic_crtc/Makefile

@@ -7,7 +7,7 @@ ehbasic: ehbasic.o
 	$(LD) -C symon.config -vm -m ehbasic.map -o ehbasic.rom ehbasic.o
 
 ehbasic.o:
-	$(CA) --listing -o ehbasic.o min_mon.asm
+	$(CA) --listing ehbasic.lst -o ehbasic.o min_mon.asm
 
 clean:
 	rm -f *.o *.rom *.map *.lst

samples/ehbasic_crtc/symon.config

@@ -1,5 +1,5 @@
 MEMORY {
-RAM1: start = $0000, size = $8000;
+RAM1: start = $0000, size = $8000 - __STACKSIZE__;
 ROM1: start = $C000, size = $3C00, fill = yes;
 MONITOR: start = $FC00, size = $3FA, fill = yes;
 ROMV: start = $FFFA, size = $6, file = %O, fill = yes;
@@ -13,6 +13,6 @@ VECTORS:  load = ROMV, type = ro;
 }
 
 SYMBOLS {
-__STACKSIZE__ = $0300;
+__STACKSIZE__: type = weak, value = $0300;
 }
 

src/main/java/com/loomcom/symon/Breakpoints.java

@@ -0,0 +1,85 @@
+package com.loomcom.symon;
+
+import com.loomcom.symon.exceptions.MemoryAccessException;
+import com.loomcom.symon.util.Utils;
+
+import javax.swing.table.AbstractTableModel;
+import java.util.ArrayList;
+import java.util.TreeSet;
+
+public class Breakpoints extends AbstractTableModel {
+
+    private TreeSet<Integer> breakpoints;
+    private Simulator simulator;
+
+    public Breakpoints(Simulator simulator) {
+        this.breakpoints = new TreeSet<>();
+        this.simulator = simulator;
+    }
+
+    public boolean contains(int address) {
+        return this.breakpoints.contains(address);
+    }
+
+    public void addBreakpoint(int address) {
+        this.breakpoints .add(address);
+        fireTableDataChanged();
+    }
+
+    public void removeBreakpoint(int address) {
+        this.breakpoints.remove(address);
+        fireTableDataChanged();
+    }
+
+    public void removeBreakpointAtIndex(int index) {
+        if (index < 0) {
+            return;
+        }
+
+        ArrayList<Integer> values = new ArrayList<>(breakpoints);
+        int value = values.get(index);
+        this.breakpoints.remove(value);
+        fireTableDataChanged();
+    }
+
+    public void refresh() {
+        fireTableDataChanged();
+    }
+
+    @Override
+    public String getColumnName(int index) {
+        if (index == 0) {
+            return "Address";
+        } else {
+            return "Inst";
+        }
+    }
+
+    @Override
+    public int getRowCount() {
+        return breakpoints.size();
+    }
+
+    @Override
+    public int getColumnCount() {
+        return 2;
+    }
+
+    @Override
+    public Object getValueAt(int rowIndex, int columnIndex) {
+        ArrayList<Integer> values = new ArrayList<>(breakpoints);
+
+        if (columnIndex == 0) {
+            return "$" + Utils.wordToHex(values.get(rowIndex));
+        } else if (columnIndex == 1) {
+            int address = values.get(rowIndex);
+            try {
+                return simulator.disassembleOpAtAddress(address);
+            } catch (MemoryAccessException ex) {
+                return "???";
+            }
+        } else {
+            return null;
+        }
+    }
+}

src/main/java/com/loomcom/symon/Bus.java

@@ -26,6 +26,7 @@ package com.loomcom.symon;
 import com.loomcom.symon.devices.Device;
 import com.loomcom.symon.exceptions.MemoryAccessException;
 import com.loomcom.symon.exceptions.MemoryRangeException;
+
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -34,7 +35,6 @@ import java.util.Map;
 
 import java.util.SortedSet;
 import java.util.TreeSet;
-import java.util.stream.Collectors;
 
 /**
  * The Bus ties the whole thing together, man.
@@ -43,7 +43,7 @@ public class Bus {
 
     // The default address at which to load programs
     public static int DEFAULT_LOAD_ADDRESS = 0x0200;
-	
+
     // By default, our bus starts at 0, and goes up to 64K
     private int startAddress = 0x0000;
     private int endAddress = 0xffff;
@@ -53,10 +53,10 @@ public class Bus {
 
     // Ordered sets of IO devices, associated with their priority
     private Map<Integer, SortedSet<Device>> deviceMap;
-    
+
     // an array for quick lookup of adresses, brute-force style
     private Device[] deviceAddressArray;
-    
+
 
     public Bus(int size) {
         this(0, size - 1);
@@ -75,30 +75,30 @@ public class Bus {
     public int endAddress() {
         return endAddress;
     }
-    
+
     private void buildDeviceAddressArray() {
         int size = (this.endAddress - this.startAddress) + 1;
         deviceAddressArray = new Device[size];
-   
+
         // getDevices() provides an OrderedSet with devices ordered by priorities
-        for(Device device : getDevices()) {
+        for (Device device : getDevices()) {
             MemoryRange range = device.getMemoryRange();
-            for(int address = range.startAddress; address <= range.endAddress; ++address) {
+            for (int address = range.startAddress; address <= range.endAddress; ++address) {
                 deviceAddressArray[address - this.startAddress] = device;
             }
         }
-        
+
     }
 
     /**
      * Add a device to the bus.
      *
-     * @param device Device to add
+     * @param device   Device to add
      * @param priority Bus prioirity.
      * @throws MemoryRangeException
      */
     public void addDevice(Device device, int priority) throws MemoryRangeException {
-        
+
         MemoryRange range = device.getMemoryRange();
 
         if (range.startAddress() < this.startAddress || range.startAddress() > this.endAddress) {
@@ -115,12 +115,12 @@ public class Bus {
             deviceSet = new TreeSet<>();
             deviceMap.put(priority, deviceSet);
         }
-        
+
         device.setBus(this);
         deviceSet.add(device);
         buildDeviceAddressArray();
     }
-    
+
     /**
      * Add a device to the bus. Throws a MemoryRangeException if the device overlaps with any others.
      *
@@ -130,7 +130,7 @@ public class Bus {
     public void addDevice(Device device) throws MemoryRangeException {
         addDevice(device, 0);
     }
-    
+
 
     /**
      * Remove a device from the bus.
@@ -138,7 +138,7 @@ public class Bus {
      * @param device Device to remove
      */
     public void removeDevice(Device device) {
-        for(SortedSet<Device> deviceSet : deviceMap.values()) {
+        for (SortedSet<Device> deviceSet : deviceMap.values()) {
             deviceSet.remove(device);
         }
         buildDeviceAddressArray();
@@ -155,39 +155,39 @@ public class Bus {
      * device.
      */
     public boolean isComplete() {
-        if(deviceAddressArray == null) {
+        if (deviceAddressArray == null) {
             buildDeviceAddressArray();
         }
-        
-        for(int address = startAddress; address <= endAddress; ++address) {
-            if(deviceAddressArray[address - startAddress] == null) {
+
+        for (int address = startAddress; address <= endAddress; ++address) {
+            if (deviceAddressArray[address - startAddress] == null) {
                 return false;
             }
         }
-        
+
         return true;
     }
 
     public int read(int address) throws MemoryAccessException {
         Device d = deviceAddressArray[address - this.startAddress];
-        if(d != null) {
+        if (d != null) {
             MemoryRange range = d.getMemoryRange();
             int devAddr = address - range.startAddress();
             return d.read(devAddr) & 0xff;
         }
-        
+
         throw new MemoryAccessException("Bus read failed. No device at address " + String.format("$%04X", address));
     }
 
     public void write(int address, int value) throws MemoryAccessException {
         Device d = deviceAddressArray[address - this.startAddress];
-        if(d != null) {
+        if (d != null) {
             MemoryRange range = d.getMemoryRange();
             int devAddr = address - range.startAddress();
             d.write(devAddr, value);
             return;
         }
-        
+
         throw new MemoryAccessException("Bus write failed. No device at address " + String.format("$%04X", address));
     }
 
@@ -218,15 +218,17 @@ public class Bus {
     public SortedSet<Device> getDevices() {
         // create an ordered set of devices, ordered by device priorities
         SortedSet<Device> devices = new TreeSet<>();
-        
+
         List<Integer> priorities = new ArrayList<>(deviceMap.keySet());
         Collections.sort(priorities);
-        
-        for(int priority : priorities) {
+
+        for (int priority : priorities) {
             SortedSet<Device> deviceSet = deviceMap.get(priority);
-            devices.addAll(deviceSet.stream().collect(Collectors.toList()));
+            for (Device device : deviceSet) {
+                devices.add(device);
+            }
         }
-        
+
         return devices;
     }
 

src/main/java/com/loomcom/symon/Cpu.java

@@ -24,7 +24,7 @@
 package com.loomcom.symon;
 
 import com.loomcom.symon.exceptions.MemoryAccessException;
-import com.loomcom.symon.util.HexUtil;
+import com.loomcom.symon.util.Utils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -70,7 +70,7 @@ public class Cpu implements InstructionTable {
     private Bus bus;
 
     /* The CPU state */
-    private static final CpuState state = new CpuState();
+    private final CpuState state = new CpuState();
 
     /* start time of op execution, needed for speed simulation */
     private long opBeginTime;
@@ -79,7 +79,7 @@ public class Cpu implements InstructionTable {
      * Construct a new CPU.
      */
     public Cpu() {
-        this(CpuBehavior.NMOS_WITH_INDIRECT_JMP_BUG);
+        this(CpuBehavior.NMOS_6502);
     }
 
     public Cpu(CpuBehavior behavior) {
@@ -114,7 +114,7 @@ public class Cpu implements InstructionTable {
         state.sp = 0xff;
 
         // Set the PC to the address stored in the reset vector
-        state.pc = address(bus.read(RST_VECTOR_L), bus.read(RST_VECTOR_H));
+        state.pc = Utils.address(bus.read(RST_VECTOR_L), bus.read(RST_VECTOR_H));
 
         // Clear instruction register.
         state.ir = 0;
@@ -202,7 +202,14 @@ public class Cpu implements InstructionTable {
                     case 2: // Accumulator - ignored
                         break;
                     case 3: // Absolute
-                        effectiveAddress = address(state.args[0], state.args[1]);
+                        effectiveAddress = Utils.address(state.args[0], state.args[1]);
+                        break;
+                    case 4: // 65C02 (Zero Page)
+                        if (behavior == CpuBehavior.CMOS_6502 ||
+                            behavior == CpuBehavior.CMOS_65816) {
+                            effectiveAddress = Utils.address(bus.read(state.args[0]),
+                                                             bus.read((state.args[0] + 1) & 0xff));
+                        }
                         break;
                     case 5: // Zero Page,X / Zero Page,Y
                         if (state.ir == 0x96 || state.ir == 0xb6) {
@@ -224,7 +231,7 @@ public class Cpu implements InstructionTable {
                 switch (irAddressMode) {
                     case 0: // (Zero Page,X)
                         tmp = (state.args[0] + state.x) & 0xff;
-                        effectiveAddress = address(bus.read(tmp), bus.read(tmp + 1));
+                        effectiveAddress = Utils.address(bus.read(tmp), bus.read(tmp + 1));
                         break;
                     case 1: // Zero Page
                         effectiveAddress = state.args[0];
@@ -233,10 +240,10 @@ public class Cpu implements InstructionTable {
                         effectiveAddress = -1;
                         break;
                     case 3: // Absolute
-                        effectiveAddress = address(state.args[0], state.args[1]);
+                        effectiveAddress = Utils.address(state.args[0], state.args[1]);
                         break;
                     case 4: // (Zero Page),Y
-                        tmp = address(bus.read(state.args[0]),
+                        tmp = Utils.address(bus.read(state.args[0]),
                                       bus.read((state.args[0] + 1) & 0xff));
                         effectiveAddress = (tmp + state.y) & 0xffff;
                         break;
@@ -258,13 +265,11 @@ public class Cpu implements InstructionTable {
 
             /** Single Byte Instructions; Implied and Relative **/
             case 0x00: // BRK - Force Interrupt - Implied
-                if (!getIrqDisableFlag()) {
-                    handleIrq(state.pc + 1);
-                }
+                handleBrk(state.pc + 1);
                 break;
             case 0x08: // PHP - Push Processor Status - Implied
                 // Break flag is always set in the stack value.
-                stackPush(state.getStatusFlag() | 0x10); 
+                stackPush(state.getStatusFlag() | 0x10);
                 break;
             case 0x10: // BPL - Branch if Positive - Relative
                 if (!getNegativeFlag()) {
@@ -277,7 +282,7 @@ public class Cpu implements InstructionTable {
             case 0x20: // JSR - Jump to Subroutine - Implied
                 stackPush((state.pc - 1 >> 8) & 0xff); // PC high byte
                 stackPush(state.pc - 1 & 0xff);        // PC low byte
-                state.pc = address(state.args[0], state.args[1]);
+                state.pc = Utils.address(state.args[0], state.args[1]);
                 break;
             case 0x28: // PLP - Pull Processor Status - Implied
                 setProcessorStatus(stackPop());
@@ -294,7 +299,7 @@ public class Cpu implements InstructionTable {
                 setProcessorStatus(stackPop());
                 int lo = stackPop();
                 int hi = stackPop();
-                setProgramCounter(address(lo, hi));
+                setProgramCounter(Utils.address(lo, hi));
                 break;
             case 0x48: // PHA - Push Accumulator - Implied
                 stackPush(state.a);
@@ -310,7 +315,7 @@ public class Cpu implements InstructionTable {
             case 0x60: // RTS - Return from Subroutine - Implied
                 lo = stackPop();
                 hi = stackPop();
-                setProgramCounter((address(lo, hi) + 1) & 0xffff);
+                setProgramCounter((Utils.address(lo, hi) + 1) & 0xffff);
                 break;
             case 0x68: // PLA - Pull Accumulator - Implied
                 state.a = stackPop();
@@ -398,20 +403,21 @@ public class Cpu implements InstructionTable {
 
             /** JMP *****************************************************************/
             case 0x4c: // JMP - Absolute
-                state.pc = address(state.args[0], state.args[1]);
+                state.pc = Utils.address(state.args[0], state.args[1]);
                 break;
+            // TODO: 65C02 instruction 0x7C, JMP (Indirect,X)
             case 0x6c: // JMP - Indirect
-                lo = address(state.args[0], state.args[1]); // Address of low byte
+                lo = Utils.address(state.args[0], state.args[1]); // Address of low byte
 
                 if (state.args[0] == 0xff &&
-                    (behavior == CpuBehavior.NMOS_WITH_INDIRECT_JMP_BUG ||
+                    (behavior == CpuBehavior.NMOS_6502 ||
                      behavior == CpuBehavior.NMOS_WITH_ROR_BUG)) {
-                    hi = address(0x00, state.args[1]);
+                    hi = Utils.address(0x00, state.args[1]);
                 } else {
                     hi = lo + 1;
                 }
 
-                state.pc = address(bus.read(lo), bus.read(hi));
+                state.pc = Utils.address(bus.read(lo), bus.read(hi));
                 /* TODO: For accuracy, allow a flag to enable broken behavior of early 6502s:
                  *
                  * "An original 6502 has does not correctly fetch the target
@@ -424,13 +430,20 @@ public class Cpu implements InstructionTable {
                  * (http://www.obelisk.demon.co.uk/6502/reference.html#JMP)
                  */
                 break;
-
+            case 0x7C: // 65C02 JMP - Absolute,X
+                state.pc = (Utils.address(state.args[0], state.args[1]) + state.x) & 0xffff;
+                break;
 
             /** ORA - Logical Inclusive Or ******************************************/
             case 0x09: // #Immediate
                 state.a |= state.args[0];
                 setArithmeticFlags(state.a);
                 break;
+            case 0x12: // 65C02 ORA (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0x01: // (Zero Page,X)
             case 0x05: // Zero Page
             case 0x0d: // Absolute
@@ -473,6 +486,11 @@ public class Cpu implements InstructionTable {
                 state.a &= state.args[0];
                 setArithmeticFlags(state.a);
                 break;
+            case 0x32: // 65C02 AND (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0x21: // (Zero Page,X)
             case 0x25: // Zero Page
             case 0x2d: // Absolute
@@ -505,6 +523,11 @@ public class Cpu implements InstructionTable {
                 state.a ^= state.args[0];
                 setArithmeticFlags(state.a);
                 break;
+            case 0x52: // 65C02 EOR (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0x41: // (Zero Page,X)
             case 0x45: // Zero Page
             case 0x4d: // Absolute
@@ -540,6 +563,11 @@ public class Cpu implements InstructionTable {
                     state.a = adc(state.a, state.args[0]);
                 }
                 break;
+            case 0x72: // 65C02 ADC (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0x61: // (Zero Page,X)
             case 0x65: // Zero Page
             case 0x6d: // Absolute
@@ -571,6 +599,11 @@ public class Cpu implements InstructionTable {
 
 
             /** STA - Store Accumulator *********************************************/
+            case 0x92: // 65C02 STA (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0x81: // (Zero Page,X)
             case 0x85: // Zero Page
             case 0x8d: // Absolute
@@ -631,6 +664,11 @@ public class Cpu implements InstructionTable {
                 state.a = state.args[0];
                 setArithmeticFlags(state.a);
                 break;
+            case 0xb2: // 65C02 LDA (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0xa1: // (Zero Page,X)
             case 0xa5: // Zero Page
             case 0xad: // Absolute
@@ -657,6 +695,11 @@ public class Cpu implements InstructionTable {
             case 0xc9: // #Immediate
                 cmp(state.a, state.args[0]);
                 break;
+            case 0xd2: // 65C02 CMP (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0xc1: // (Zero Page,X)
             case 0xc5: // Zero Page
             case 0xcd: // Absolute
@@ -697,6 +740,11 @@ public class Cpu implements InstructionTable {
                     state.a = sbc(state.a, state.args[0]);
                 }
                 break;
+            case 0xf2: // 65C02 SBC (ZP)
+                if (behavior == CpuBehavior.NMOS_6502 ||
+                    behavior == CpuBehavior.NMOS_WITH_ROR_BUG) {
+                    break;
+                }
             case 0xe1: // (Zero Page,X)
             case 0xe5: // Zero Page
             case 0xed: // Absolute
@@ -744,13 +792,18 @@ public class Cpu implements InstructionTable {
         }
     }
 
+    private void handleBrk(int returnPc) throws MemoryAccessException {
+        handleInterrupt(returnPc, IRQ_VECTOR_L, IRQ_VECTOR_H, true);
+        clearIrq();
+    }
+
     private void handleIrq(int returnPc) throws MemoryAccessException {
-        handleInterrupt(returnPc, IRQ_VECTOR_L, IRQ_VECTOR_H);
+        handleInterrupt(returnPc, IRQ_VECTOR_L, IRQ_VECTOR_H, false);
         clearIrq();
     }
 
     private void handleNmi() throws MemoryAccessException {
-        handleInterrupt(state.pc, NMI_VECTOR_L, NMI_VECTOR_H);
+        handleInterrupt(state.pc, NMI_VECTOR_L, NMI_VECTOR_H, false);
         clearNmi();
     }
 
@@ -759,9 +812,19 @@ public class Cpu implements InstructionTable {
      *
      * @throws MemoryAccessException
      */
-    private void handleInterrupt(int returnPc, int vectorLow, int vectorHigh) throws MemoryAccessException {
-        // Set the break flag before pushing.
-        setBreakFlag();
+    private void handleInterrupt(int returnPc, int vectorLow, int vectorHigh, boolean isBreak) throws MemoryAccessException {
+
+        if (isBreak)
+        {
+            // Set the break flag before pushing.
+            setBreakFlag();
+        }
+        else
+        {
+            // IRQ & NMI clear break flag
+            clearBreakFlag();
+        }
+
         // Push program counter + 1 onto the stack
         stackPush((returnPc >> 8) & 0xff); // PC high byte
         stackPush(returnPc & 0xff);        // PC low byte
@@ -770,7 +833,7 @@ public class Cpu implements InstructionTable {
         setIrqDisableFlag();
 
         // Load interrupt vector address into PC
-        state.pc = address(bus.read(vectorLow), bus.read(vectorHigh));
+        state.pc = Utils.address(bus.read(vectorLow), bus.read(vectorHigh));
     }
 
     /**
@@ -1198,23 +1261,23 @@ public class Cpu implements InstructionTable {
     }
 
     public String getAccumulatorStatus() {
-        return "$" + HexUtil.byteToHex(state.a);
+        return "$" + Utils.byteToHex(state.a);
     }
 
     public String getXRegisterStatus() {
-        return "$" + HexUtil.byteToHex(state.x);
+        return "$" + Utils.byteToHex(state.x);
     }
 
     public String getYRegisterStatus() {
-        return "$" + HexUtil.byteToHex(state.y);
+        return "$" + Utils.byteToHex(state.y);
     }
 
     public String getProgramCounterStatus() {
-        return "$" + HexUtil.wordToHex(state.pc);
+        return "$" + Utils.wordToHex(state.pc);
     }
 
     public String getStackPointerStatus() {
-        return "$" + HexUtil.byteToHex(state.sp);
+        return "$" + Utils.byteToHex(state.sp);
     }
 
     public int getProcessorStatus() {
@@ -1298,19 +1361,12 @@ public class Cpu implements InstructionTable {
         }
     }
 
-    /**
-     * Given two bytes, return an address.
-     */
-    int address(int lowByte, int hiByte) {
-        return ((hiByte << 8) | lowByte) & 0xffff;
-    }
-
     /**
      * Given a hi byte and a low byte, return the Absolute,X
      * offset address.
      */
     int xAddress(int lowByte, int hiByte) {
-        return (address(lowByte, hiByte) + state.x) & 0xffff;
+        return (Utils.address(lowByte, hiByte) + state.x) & 0xffff;
     }
 
     /**
@@ -1318,7 +1374,7 @@ public class Cpu implements InstructionTable {
      * offset address.
      */
     int yAddress(int lowByte, int hiByte) {
-        return (address(lowByte, hiByte) + state.y) & 0xffff;
+        return (Utils.address(lowByte, hiByte) + state.y) & 0xffff;
     }
 
     /**
@@ -1328,6 +1384,13 @@ public class Cpu implements InstructionTable {
         return (zp + state.x) & 0xff;
     }
 
+    /**
+     * Given a single byte, compute the Zero Page,Y offset address.
+     */
+    int zpyAddress(int zp) {
+        return (zp + state.y) & 0xff;
+    }
+
     /**
      * Given a single byte, compute the offset address.
      */
@@ -1336,21 +1399,21 @@ public class Cpu implements InstructionTable {
         return (state.pc + (byte) offset) & 0xffff;
     }
 
-    /**
-     * Given a single byte, compute the Zero Page,Y offset address.
-     */
-    int zpyAddress(int zp) {
-        return (zp + state.y) & 0xff;
-    }
-
     /*
      * Perform a busy-loop until the instruction should complete on the wall clock
      */
     private void delayLoop(int opcode) {
-        int clockSteps = Cpu.instructionClocks[0xff & opcode];
+        final int clockSteps;
+
+        if (behavior == CpuBehavior.NMOS_WITH_ROR_BUG ||
+            behavior == CpuBehavior.NMOS_6502) {
+            clockSteps = Cpu.instructionClocksNmos[0xff & opcode];
+        } else {
+            clockSteps = Cpu.instructionClocksCmos[0xff & opcode];
+        }
 
         if (clockSteps == 0) {
-            logger.warn("Opcode {} has clock step of 0!", opcode);
+            logger.warn("Opcode {} has clock step of 0!", String.format("0x%02x", opcode));
             return;
         }
 
@@ -1362,249 +1425,81 @@ public class Cpu implements InstructionTable {
         } while (opBeginTime + interval >= end);
     }
 
+    /**
+     * Return a formatted string representing the last instruction and
+     * operands that were executed.
+     *
+     * @return A string representing the mnemonic and operands of the instruction
+     */
+    public static String disassembleOp(int opCode, int[] args) {
+        String mnemonic = opcodeNames[opCode];
+
+        if (mnemonic == null) {
+            return "???";
+        }
+
+        StringBuilder sb = new StringBuilder(mnemonic);
+
+        switch (instructionModes[opCode]) {
+            case ABS:
+                sb.append(" $").append(Utils.wordToHex(Utils.address(args[0], args[1])));
+                break;
+            case ABX:
+                sb.append(" $").append(Utils.wordToHex(Utils.address(args[0], args[1]))).append(",X");
+                break;
+            case ABY:
+                sb.append(" $").append(Utils.wordToHex(Utils.address(args[0], args[1]))).append(",Y");
+                break;
+            case IMM:
+                sb.append(" #$").append(Utils.byteToHex(args[0]));
+                break;
+            case IND:
+                sb.append(" ($").append(Utils.wordToHex(Utils.address(args[0], args[1]))).append(")");
+                break;
+            case XIN:
+                sb.append(" ($").append(Utils.byteToHex(args[0])).append(",X)");
+                break;
+            case INY:
+                sb.append(" ($").append(Utils.byteToHex(args[0])).append("),Y");
+                break;
+            case REL:
+            case ZPG:
+                sb.append(" $").append(Utils.byteToHex(args[0]));
+                break;
+            case ZPX:
+                sb.append(" $").append(Utils.byteToHex(args[0])).append(",X");
+                break;
+            case ZPY:
+                sb.append(" $").append(Utils.byteToHex(args[0])).append(",Y");
+                break;
+        }
+
+        return sb.toString();
+    }
 
     /**
-     * A compact, struct-like representation of CPU state.
+     * Return a formatted string representing the next instruction and
+     * operands to be executed.
+     *
+     * @return A string representing the mnemonic and operands of the instruction
      */
-    public static class CpuState {
-        /**
-         * Accumulator
-         */
-        public int a;
-        /**
-         * X index regsiter
-         */
-        public int x;
-        /**
-         * Y index register
-         */
-        public int y;
-        /**
-         * Stack Pointer
-         */
-        public int sp;
-        /**
-         * Program Counter
-         */
-        public int pc;
-        /**
-         * Last Loaded Instruction Register
-         */
-        public int ir;
-        /**
-         * Peek-Ahead to next IR
-         */
-        public int nextIr;
-        public int[] args = new int[2];
-        public int[] nextArgs = new int[2];
-        public int instSize;
-        public boolean opTrap;
-        public boolean irqAsserted;
-        public boolean nmiAsserted;
-        public int lastPc;
+    public String disassembleNextOp() {
+        return Cpu.disassembleOp(state.nextIr, state.nextArgs);
+    }
 
-        /* Status Flag Register bits */
-        public boolean carryFlag;
-        public boolean negativeFlag;
-        public boolean zeroFlag;
-        public boolean irqDisableFlag;
-        public boolean decimalModeFlag;
-        public boolean breakFlag;
-        public boolean overflowFlag;
-        public long stepCounter = 0L;
-
-        /**
-         * Create an empty CPU State.
-         */
-        public CpuState() {}
-
-        /**
-         * Snapshot a copy of the CpuState.
-         *
-         * (This is a copy constructor rather than an implementation of <code>Cloneable</code>
-         * based on Josh Bloch's recommendation)
-         *
-         * @param s The CpuState to copy.
-         */
-        public CpuState(CpuState s) {
-            this.a = s.a;
-            this.x = s.x;
-            this.y = s.y;
-            this.sp = s.sp;
-            this.pc = s.pc;
-            this.ir = s.ir;
-            this.nextIr = s.nextIr;
-            this.lastPc = s.lastPc;
-            this.args[0] = s.args[0];
-            this.args[1] = s.args[1];
-            this.nextArgs[0] = s.nextArgs[0];
-            this.nextArgs[1] = s.nextArgs[1];
-            this.instSize = s.instSize;
-            this.opTrap = s.opTrap;
-            this.irqAsserted = s.irqAsserted;
-            this.carryFlag = s.carryFlag;
-            this.negativeFlag = s.negativeFlag;
-            this.zeroFlag = s.zeroFlag;
-            this.irqDisableFlag = s.irqDisableFlag;
-            this.decimalModeFlag = s.decimalModeFlag;
-            this.breakFlag = s.breakFlag;
-            this.overflowFlag = s.overflowFlag;
-            this.stepCounter = s.stepCounter;
+    /**
+     * @param address Address to disassemble
+     * @return String containing the disassembled instruction and operands.
+     */
+    public String disassembleOpAtAddress(int address) throws MemoryAccessException {
+        int opCode = bus.read(address);
+        int args[] = new int[2];
+        int size = Cpu.instructionSizes[opCode];
+        for (int i = 1; i < size; i++) {
+            int nextRead = (address + i) % bus.endAddress();
+            args[i-1] = bus.read(nextRead);
         }
 
-        /**
-         * Returns a string formatted for the trace log.
-         *
-         * @return a string formatted for the trace log.
-         */
-        public String toTraceEvent() {
-            String opcode = disassembleLastOp();
-            return getInstructionByteStatus() + "  " +
-                    String.format("%-14s", opcode) +
-                    "A:" + HexUtil.byteToHex(a) + " " +
-                    "X:" + HexUtil.byteToHex(x) + " " +
-                    "Y:" + HexUtil.byteToHex(y) + " " +
-                    "F:" + HexUtil.byteToHex(getStatusFlag()) + " " +
-                    "S:1" + HexUtil.byteToHex(sp) + " " +
-                    getProcessorStatusString() + "\n";
-        }
-
-        /**
-         * @return The value of the Process Status Register, as a byte.
-         */
-        public int getStatusFlag() {
-            int status = 0x20;
-            if (carryFlag) {
-                status |= P_CARRY;
-            }
-            if (zeroFlag) {
-                status |= P_ZERO;
-            }
-            if (irqDisableFlag) {
-                status |= P_IRQ_DISABLE;
-            }
-            if (decimalModeFlag) {
-                status |= P_DECIMAL;
-            }
-            if (breakFlag) {
-                status |= P_BREAK;
-            }
-            if (overflowFlag) {
-                status |= P_OVERFLOW;
-            }
-            if (negativeFlag) {
-                status |= P_NEGATIVE;
-            }
-            return status;
-        }
-
-        public String getInstructionByteStatus() {
-            switch (Cpu.instructionSizes[ir]) {
-                case 0:
-                case 1:
-                    return HexUtil.wordToHex(lastPc) + "  " +
-                           HexUtil.byteToHex(ir) + "      ";
-                case 2:
-                    return HexUtil.wordToHex(lastPc) + "  " +
-                           HexUtil.byteToHex(ir) + " " +
-                           HexUtil.byteToHex(args[0]) + "   ";
-                case 3:
-                    return HexUtil.wordToHex(lastPc) + "  " +
-                           HexUtil.byteToHex(ir) + " " +
-                           HexUtil.byteToHex(args[0]) + " " +
-                           HexUtil.byteToHex(args[1]);
-                default:
-                    return null;
-            }
-        }
-
-        /**
-         * Return a formatted string representing the last instruction and
-         * operands that were executed.
-         *
-         * @return A string representing the mnemonic and operands of the instruction
-         */
-        private String disassembleOp(int ir, int[] args) {
-            String mnemonic = opcodeNames[ir];
-
-            if (mnemonic == null) {
-                return "???";
-            }
-
-            StringBuilder sb = new StringBuilder(mnemonic);
-
-            switch (instructionModes[ir]) {
-                case ABS:
-                    sb.append(" $").append(HexUtil.wordToHex(address(args[0], args[1])));
-                    break;
-                case ABX:
-                    sb.append(" $").append(HexUtil.wordToHex(address(args[0], args[1]))).append(",X");
-                    break;
-                case ABY:
-                    sb.append(" $").append(HexUtil.wordToHex(address(args[0], args[1]))).append(",Y");
-                    break;
-                case IMM:
-                    sb.append(" #$").append(HexUtil.byteToHex(args[0]));
-                    break;
-                case IND:
-                    sb.append(" ($").append(HexUtil.wordToHex(address(args[0], args[1]))).append(")");
-                    break;
-                case XIN:
-                    sb.append(" ($").append(HexUtil.byteToHex(args[0])).append(",X)");
-                    break;
-                case INY:
-                    sb.append(" ($").append(HexUtil.byteToHex(args[0])).append("),Y");
-                    break;
-                case REL:
-                case ZPG:
-                    sb.append(" $").append(HexUtil.byteToHex(args[0]));
-                    break;
-                case ZPX:
-                    sb.append(" $").append(HexUtil.byteToHex(args[0])).append(",X");
-                    break;
-                case ZPY:
-                    sb.append(" $").append(HexUtil.byteToHex(args[0])).append(",Y");
-                    break;
-            }
-
-            return sb.toString();
-        }
-
-        public String disassembleLastOp() {
-            return disassembleOp(ir, args);
-        }
-
-        /**
-         * Return a formatted string representing the next instruction and
-         * operands to be executed.
-         *
-         * @return A string representing the mnemonic and operands of the instruction
-         */
-        public String disassembleNextOp() {
-            return disassembleOp(nextIr, nextArgs);
-        }
-
-        /**
-         * Given two bytes, return an address.
-         */
-        private int address(int lowByte, int hiByte) {
-            return ((hiByte << 8) | lowByte) & 0xffff;
-        }
-
-
-        /**
-         * @return A string representing the current status register state.
-         */
-        public String getProcessorStatusString() {
-            return "[" + (negativeFlag ? 'N' : '.') +
-                    (overflowFlag ? 'V' : '.') +
-                    "-" +
-                    (breakFlag ? 'B' : '.') +
-                    (decimalModeFlag ? 'D' : '.') +
-                    (irqDisableFlag ? 'I' : '.') +
-                    (zeroFlag ? 'Z' : '.') +
-                    (carryFlag ? 'C' : '.') +
-                    "]";
-        }
+        return disassembleOp(opCode, args);
     }
 }

src/main/java/com/loomcom/symon/CpuState.java

@@ -0,0 +1,177 @@
+package com.loomcom.symon;
+
+import com.loomcom.symon.util.Utils;
+
+/**
+ * A compact, struct-like representation of CPU state.
+ */
+public class CpuState {
+    /**
+     * Accumulator
+     */
+    public int a;
+
+    /**
+     * X index regsiter
+     */
+    public int x;
+
+    /**
+     * Y index register
+     */
+    public int y;
+
+    /**
+     * Stack Pointer
+     */
+    public int sp;
+
+    /**
+     * Program Counter
+     */
+    public int pc;
+
+    /**
+     * Last Loaded Instruction Register
+     */
+    public int ir;
+
+    /**
+     * Peek-Ahead to next IR
+     */
+    public int nextIr;
+    public int[] args = new int[2];
+    public int[] nextArgs = new int[2];
+    public int instSize;
+    public boolean opTrap;
+    public boolean irqAsserted;
+    public boolean nmiAsserted;
+    public int lastPc;
+
+    /* Status Flag Register bits */
+    public boolean carryFlag;
+    public boolean negativeFlag;
+    public boolean zeroFlag;
+    public boolean irqDisableFlag;
+    public boolean decimalModeFlag;
+    public boolean breakFlag;
+    public boolean overflowFlag;
+    public long stepCounter = 0L;
+
+    public CpuState() {}
+
+    /**
+     * Snapshot a copy of the CpuState.
+     *
+     * (This is a copy constructor rather than an implementation of <code>Cloneable</code>
+     * based on Josh Bloch's recommendation)
+     *
+     * @param s The CpuState to copy.
+     */
+    public CpuState(CpuState s) {
+        this.a = s.a;
+        this.x = s.x;
+        this.y = s.y;
+        this.sp = s.sp;
+        this.pc = s.pc;
+        this.ir = s.ir;
+        this.nextIr = s.nextIr;
+        this.lastPc = s.lastPc;
+        this.args[0] = s.args[0];
+        this.args[1] = s.args[1];
+        this.nextArgs[0] = s.nextArgs[0];
+        this.nextArgs[1] = s.nextArgs[1];
+        this.instSize = s.instSize;
+        this.opTrap = s.opTrap;
+        this.irqAsserted = s.irqAsserted;
+        this.carryFlag = s.carryFlag;
+        this.negativeFlag = s.negativeFlag;
+        this.zeroFlag = s.zeroFlag;
+        this.irqDisableFlag = s.irqDisableFlag;
+        this.decimalModeFlag = s.decimalModeFlag;
+        this.breakFlag = s.breakFlag;
+        this.overflowFlag = s.overflowFlag;
+        this.stepCounter = s.stepCounter;
+    }
+
+    /**
+     * Returns a string formatted for the trace log.
+     *
+     * @return a string formatted for the trace log.
+     */
+    public String toTraceEvent() {
+        String opcode = Cpu.disassembleOp(ir, args);
+        return getInstructionByteStatus() + "  " +
+                String.format("%-14s", opcode) +
+                "A:" + Utils.byteToHex(a) + " " +
+                "X:" + Utils.byteToHex(x) + " " +
+                "Y:" + Utils.byteToHex(y) + " " +
+                "F:" + Utils.byteToHex(getStatusFlag()) + " " +
+                "S:1" + Utils.byteToHex(sp) + " " +
+                getProcessorStatusString() + "\n";
+    }
+
+    /**
+     * @return The value of the Process Status Register, as a byte.
+     */
+    public int getStatusFlag() {
+        int status = 0x20;
+        if (carryFlag) {
+            status |= Cpu.P_CARRY;
+        }
+        if (zeroFlag) {
+            status |= Cpu.P_ZERO;
+        }
+        if (irqDisableFlag) {
+            status |= Cpu.P_IRQ_DISABLE;
+        }
+        if (decimalModeFlag) {
+            status |= Cpu.P_DECIMAL;
+        }
+        if (breakFlag) {
+            status |= Cpu.P_BREAK;
+        }
+        if (overflowFlag) {
+            status |= Cpu.P_OVERFLOW;
+        }
+        if (negativeFlag) {
+            status |= Cpu.P_NEGATIVE;
+        }
+        return status;
+    }
+
+    public String getInstructionByteStatus() {
+        switch (Cpu.instructionSizes[ir]) {
+            case 0:
+            case 1:
+                return Utils.wordToHex(lastPc) + "  " +
+                       Utils.byteToHex(ir) + "      ";
+            case 2:
+                return Utils.wordToHex(lastPc) + "  " +
+                       Utils.byteToHex(ir) + " " +
+                       Utils.byteToHex(args[0]) + "   ";
+            case 3:
+                return Utils.wordToHex(lastPc) + "  " +
+                       Utils.byteToHex(ir) + " " +
+                       Utils.byteToHex(args[0]) + " " +
+                       Utils.byteToHex(args[1]);
+            default:
+                return null;
+        }
+    }
+
+    /**
+     * @return A string representing the current status register state.
+     */
+    public String getProcessorStatusString() {
+        return "[" + (negativeFlag ? 'N' : '.') +
+                (overflowFlag ? 'V' : '.') +
+                "-" +
+                (breakFlag ? 'B' : '.') +
+                (decimalModeFlag ? 'D' : '.') +
+                (irqDisableFlag ? 'I' : '.') +
+                (zeroFlag ? 'Z' : '.') +
+                (carryFlag ? 'C' : '.') +
+                "]";
+    }
+}

src/main/java/com/loomcom/symon/InstructionTable.java

@@ -46,20 +46,17 @@ public interface InstructionTable {
          *
          * NB: Does NOT implement "unimplemented" NMOS instructions.
          */
-        NMOS_WITH_INDIRECT_JMP_BUG,
-
-        /**
-         * Emulate an NMOS 6502 without the indirect JMP bug. This type of 6502
-         * does not actually exist in the wild.
-         *
-         * NB: Does NOT implement "unimplemented" NMOS instructions.
-         */
-        NMOS_WITHOUT_INDIRECT_JMP_BUG,
+        NMOS_6502,
 
         /**
          * Emulate a CMOS 65C02, with all CMOS instructions and addressing modes.
          */
-        CMOS
+        CMOS_6502,
+
+        /**
+         * Emulate a CMOS 65C816.
+         */
+        CMOS_65816
     }
 
     /**
@@ -128,19 +125,25 @@ public interface InstructionTable {
 
         ZPG {
             public String toString() {
-                return "Zeropage";
+                return "Zero Page";
             }
         },
 
         ZPX {
             public String toString() {
-                return "Zeropage, X-indexed";
+                return "Zero Page, X-indexed";
             }
         },
 
         ZPY {
             public String toString() {
-                return "Zeropage, Y-indexed";
+                return "Zero Page, Y-indexed";
+            }
+        },
+
+        ZPI {
+            public String toString() {
+                return "Zero Page Indirect";
             }
         },
 
@@ -154,52 +157,55 @@ public interface InstructionTable {
     // 6502 opcodes.  No 65C02 opcodes implemented.
 
     /**
-     * Instruction opcode names.
+     * Instruction opcode names. This lists all opcodes for
+     * NMOS 6502, CMOS 65C02, and CMOS 65C816
      */
     String[] opcodeNames = {
-        "BRK", "ORA",  null,  null,  null, "ORA", "ASL",  null,
-        "PHP", "ORA", "ASL",  null,  null, "ORA", "ASL",  null,
-        "BPL", "ORA",  null,  null,  null, "ORA", "ASL",  null,
-        "CLC", "ORA",  null,  null,  null, "ORA", "ASL",  null,
-        "JSR", "AND",  null,  null, "BIT", "AND", "ROL",  null,
-        "PLP", "AND", "ROL",  null, "BIT", "AND", "ROL",  null,
-        "BMI", "AND",  null,  null,  null, "AND", "ROL",  null,
-        "SEC", "AND",  null,  null,  null, "AND", "ROL",  null,
-        "RTI", "EOR",  null,  null,  null, "EOR", "LSR",  null,
-        "PHA", "EOR", "LSR",  null, "JMP", "EOR", "LSR",  null,
-        "BVC", "EOR",  null,  null,  null, "EOR", "LSR",  null,
-        "CLI", "EOR",  null,  null,  null, "EOR", "LSR",  null,
-        "RTS", "ADC",  null,  null,  null, "ADC", "ROR",  null,
-        "PLA", "ADC", "ROR",  null, "JMP", "ADC", "ROR",  null,
-        "BVS", "ADC",  null,  null,  null, "ADC", "ROR",  null,
-        "SEI", "ADC",  null,  null,  null, "ADC", "ROR",  null,
-        "BCS", "STA",  null,  null, "STY", "STA", "STX",  null,
-        "DEY",  null, "TXA",  null, "STY", "STA", "STX",  null,
-        "BCC", "STA",  null,  null, "STY", "STA", "STX",  null,
-        "TYA", "STA", "TXS",  null,  null, "STA",  null,  null,
-        "LDY", "LDA", "LDX",  null, "LDY", "LDA", "LDX",  null,
-        "TAY", "LDA", "TAX",  null, "LDY", "LDA", "LDX",  null,
-        "BCS", "LDA",  null,  null, "LDY", "LDA", "LDX",  null,
-        "CLV", "LDA", "TSX",  null, "LDY", "LDA", "LDX",  null,
-        "CPY", "CMP",  null,  null, "CPY", "CMP", "DEC",  null,
-        "INY", "CMP", "DEX",  null, "CPY", "CMP", "DEC",  null,
-        "BNE", "CMP",  null,  null,  null, "CMP", "DEC",  null,
-        "CLD", "CMP",  null,  null,  null, "CMP", "DEC",  null,
-        "CPX", "SBC",  null,  null, "CPX", "SBC", "INC",  null,
-        "INX", "SBC", "NOP",  null, "CPX", "SBC", "INC",  null,
-        "BEQ", "SBC",  null,  null,  null, "SBC", "INC",  null,
-        "SED", "SBC",  null,  null,  null, "SBC", "INC",  null
+        "BRK", "ORA",  null,  null,  null, "ORA", "ASL",  null,  // 0x00-0x07
+        "PHP", "ORA", "ASL",  null,  null, "ORA", "ASL",  null,  // 0x08-0x0f
+        "BPL", "ORA", "ORA",  null,  null, "ORA", "ASL",  null,  // 0x10-0x17
+        "CLC", "ORA",  null,  null,  null, "ORA", "ASL",  null,  // 0x18-0x1f
+        "JSR", "AND",  null,  null, "BIT", "AND", "ROL",  null,  // 0x20-0x27
+        "PLP", "AND", "ROL",  null, "BIT", "AND", "ROL",  null,  // 0x28-0x2f
+        "BMI", "AND", "AND",  null,  null, "AND", "ROL",  null,  // 0x30-0x37
+        "SEC", "AND",  null,  null,  null, "AND", "ROL",  null,  // 0x38-0x3f
+        "RTI", "EOR",  null,  null,  null, "EOR", "LSR",  null,  // 0x40-0x47
+        "PHA", "EOR", "LSR",  null, "JMP", "EOR", "LSR",  null,  // 0x48-0x4f
+        "BVC", "EOR", "EOR",  null,  null, "EOR", "LSR",  null,  // 0x50-0x57
+        "CLI", "EOR",  null,  null,  null, "EOR", "LSR",  null,  // 0x58-0x5f
+        "RTS", "ADC",  null,  null,  null, "ADC", "ROR",  null,  // 0x60-0x67
+        "PLA", "ADC", "ROR",  null, "JMP", "ADC", "ROR",  null,  // 0x68-0x6f
+        "BVS", "ADC", "ADC",  null,  null, "ADC", "ROR",  null,  // 0x70-0x77
+        "SEI", "ADC",  null,  null, "JMP", "ADC", "ROR",  null,  // 0x78-0x7f
+        "BCS", "STA",  null,  null, "STY", "STA", "STX",  null,  // 0x80-0x87
+        "DEY",  null, "TXA",  null, "STY", "STA", "STX",  null,  // 0x88-0x8f
+        "BCC", "STA", "STA",  null, "STY", "STA", "STX",  null,  // 0x90-0x97
+        "TYA", "STA", "TXS",  null,  null, "STA",  null,  null,  // 0x98-0x9f
+        "LDY", "LDA", "LDX",  null, "LDY", "LDA", "LDX",  null,  // 0xa0-0xa7
+        "TAY", "LDA", "TAX",  null, "LDY", "LDA", "LDX",  null,  // 0xa8-0xaf
+        "BCS", "LDA", "LDA",  null, "LDY", "LDA", "LDX",  null,  // 0xb0-0xb7
+        "CLV", "LDA", "TSX",  null, "LDY", "LDA", "LDX",  null,  // 0xb8-0xbf
+        "CPY", "CMP",  null,  null, "CPY", "CMP", "DEC",  null,  // 0xc0-0xc7
+        "INY", "CMP", "DEX",  null, "CPY", "CMP", "DEC",  null,  // 0xc8-0xcf
+        "BNE", "CMP", "CMP",  null,  null, "CMP", "DEC",  null,  // 0xd0-0xd7
+        "CLD", "CMP",  null,  null,  null, "CMP", "DEC",  null,  // 0xd8-0xdf
+        "CPX", "SBC",  null,  null, "CPX", "SBC", "INC",  null,  // 0xe0-0xe7
+        "INX", "SBC", "NOP",  null, "CPX", "SBC", "INC",  null,  // 0xe8-0xef
+        "BEQ", "SBC", "SBC",  null,  null, "SBC", "INC",  null,  // 0xf0-0xf7
+        "SED", "SBC",  null,  null,  null, "SBC", "INC",  null   // 0xf8-0xff
     };
 
     /**
-     * Instruction addressing modes.
+     * Instruction addressing modes. This table includes sizes
+     * for all instructions for NMOS 6502, CMOS 65C02,
+     * and CMOS 65C816
      */
     Mode[] instructionModes = {
         Mode.IMP, Mode.XIN, Mode.NUL, Mode.NUL,   // 0x00-0x03
         Mode.NUL, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0x04-0x07
         Mode.IMP, Mode.IMM, Mode.ACC, Mode.NUL,   // 0x08-0x0b
         Mode.NUL, Mode.ABS, Mode.ABS, Mode.NUL,   // 0x0c-0x0f
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0x10-0x13
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0x10-0x13
         Mode.NUL, Mode.ZPX, Mode.ZPX, Mode.NUL,   // 0x14-0x17
         Mode.IMP, Mode.ABY, Mode.NUL, Mode.NUL,   // 0x18-0x1b
         Mode.NUL, Mode.ABX, Mode.ABX, Mode.NUL,   // 0x1c-0x1f
@@ -207,7 +213,7 @@ public interface InstructionTable {
         Mode.ZPG, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0x24-0x27
         Mode.IMP, Mode.IMM, Mode.ACC, Mode.NUL,   // 0x28-0x2b
         Mode.ABS, Mode.ABS, Mode.ABS, Mode.NUL,   // 0x2c-0x2f
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0x30-0x33
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0x30-0x33
         Mode.NUL, Mode.ZPX, Mode.ZPX, Mode.NUL,   // 0x34-0x37
         Mode.IMP, Mode.ABY, Mode.NUL, Mode.NUL,   // 0x38-0x3b
         Mode.NUL, Mode.ABX, Mode.ABX, Mode.NUL,   // 0x3c-0x3f
@@ -215,7 +221,7 @@ public interface InstructionTable {
         Mode.NUL, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0x44-0x47
         Mode.IMP, Mode.IMM, Mode.ACC, Mode.NUL,   // 0x48-0x4b
         Mode.ABS, Mode.ABS, Mode.ABS, Mode.NUL,   // 0x4c-0x4f
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0x50-0x53
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0x50-0x53
         Mode.NUL, Mode.ZPX, Mode.ZPX, Mode.NUL,   // 0x54-0x57
         Mode.IMP, Mode.ABY, Mode.NUL, Mode.NUL,   // 0x58-0x5b
         Mode.NUL, Mode.ABX, Mode.ABX, Mode.NUL,   // 0x5c-0x5f
@@ -223,15 +229,15 @@ public interface InstructionTable {
         Mode.NUL, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0x64-0x67
         Mode.IMP, Mode.IMM, Mode.ACC, Mode.NUL,   // 0x68-0x6b
         Mode.IND, Mode.ABS, Mode.ABS, Mode.NUL,   // 0x6c-0x6f
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0x70-0x73
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0x70-0x73
         Mode.NUL, Mode.ZPX, Mode.ZPX, Mode.NUL,   // 0x74-0x77
         Mode.IMP, Mode.ABY, Mode.NUL, Mode.NUL,   // 0x78-0x7b
-        Mode.NUL, Mode.ABX, Mode.ABX, Mode.NUL,   // 0x7c-0x7f
+        Mode.ABX, Mode.ABX, Mode.ABX, Mode.NUL,   // 0x7c-0x7f
         Mode.REL, Mode.XIN, Mode.NUL, Mode.NUL,   // 0x80-0x83
         Mode.ZPG, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0x84-0x87
         Mode.IMP, Mode.NUL, Mode.IMP, Mode.NUL,   // 0x88-0x8b
         Mode.ABS, Mode.ABS, Mode.ABS, Mode.NUL,   // 0x8c-0x8f
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0x90-0x93
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0x90-0x93
         Mode.ZPX, Mode.ZPX, Mode.ZPY, Mode.NUL,   // 0x94-0x97
         Mode.IMP, Mode.ABY, Mode.IMP, Mode.NUL,   // 0x98-0x9b
         Mode.NUL, Mode.ABX, Mode.NUL, Mode.NUL,   // 0x9c-0x9f
@@ -239,7 +245,7 @@ public interface InstructionTable {
         Mode.ZPG, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0xa4-0xa7
         Mode.IMP, Mode.IMM, Mode.IMP, Mode.NUL,   // 0xa8-0xab
         Mode.ABS, Mode.ABS, Mode.ABS, Mode.NUL,   // 0xac-0xaf
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0xb0-0xb3
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0xb0-0xb3
         Mode.ZPX, Mode.ZPX, Mode.ZPY, Mode.NUL,   // 0xb4-0xb7
         Mode.IMP, Mode.ABY, Mode.IMP, Mode.NUL,   // 0xb8-0xbb
         Mode.ABX, Mode.ABX, Mode.ABY, Mode.NUL,   // 0xbc-0xbf
@@ -247,7 +253,7 @@ public interface InstructionTable {
         Mode.ZPG, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0xc4-0xc7
         Mode.IMP, Mode.IMM, Mode.IMP, Mode.NUL,   // 0xc8-0xcb
         Mode.ABS, Mode.ABS, Mode.ABS, Mode.NUL,   // 0xcc-0xcf
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0xd0-0xd3
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0xd0-0xd3
         Mode.NUL, Mode.ZPX, Mode.ZPX, Mode.NUL,   // 0xd4-0xd7
         Mode.IMP, Mode.ABY, Mode.NUL, Mode.NUL,   // 0xd8-0xdb
         Mode.NUL, Mode.ABX, Mode.ABX, Mode.NUL,   // 0xdc-0xdf
@@ -255,7 +261,7 @@ public interface InstructionTable {
         Mode.ZPG, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0xe4-0xe7
         Mode.IMP, Mode.IMM, Mode.IMP, Mode.NUL,   // 0xe8-0xeb
         Mode.ABS, Mode.ABS, Mode.ABS, Mode.NUL,   // 0xec-0xef
-        Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0xf0-0xf3
+        Mode.REL, Mode.INY, Mode.ZPI, Mode.NUL,   // 0xf0-0xf3
         Mode.NUL, Mode.ZPX, Mode.ZPX, Mode.NUL,   // 0xf4-0xf7
         Mode.IMP, Mode.ABY, Mode.NUL, Mode.NUL,   // 0xf8-0xfb
         Mode.NUL, Mode.ABX, Mode.ABX, Mode.NUL    // 0xfc-0xff
@@ -263,47 +269,73 @@ public interface InstructionTable {
 
 
     /**
-     * Size, in bytes, required for each instruction.
+     * Size, in bytes, required for each instruction. This table
+     * includes sizes for all instructions for NMOS 6502, CMOS 65C02,
+     * and CMOS 65C816
      */
     int[] instructionSizes = {
-        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 0, 3, 3, 0,
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
-        3, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
-        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
-        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
-        2, 2, 0, 0, 2, 2, 2, 0, 1, 0, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 2, 2, 2, 0, 1, 3, 1, 0, 0, 3, 0, 0,
-        2, 2, 2, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 2, 2, 2, 0, 1, 3, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
-        2, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0
+        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 0, 3, 3, 0,   // 0x00-0x0f
+        2, 2, 2, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,   // 0x10-0x1f
+        3, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0x20-0x2f
+        2, 2, 2, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,   // 0x30-0x3f
+        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0x40-0x4f
+        2, 2, 2, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,   // 0x50-0x5f
+        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0x60-0x6f
+        2, 2, 2, 0, 0, 2, 2, 0, 1, 3, 0, 0, 3, 3, 3, 0,   // 0x70-0x7f
+        2, 2, 0, 0, 2, 2, 2, 0, 1, 0, 1, 0, 3, 3, 3, 0,   // 0x80-0x8f
+        2, 2, 2, 0, 2, 2, 2, 0, 1, 3, 1, 0, 0, 3, 0, 0,   // 0x90-0x9f
+        2, 2, 2, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0xa0-0xaf
+        2, 2, 2, 0, 2, 2, 2, 0, 1, 3, 1, 0, 3, 3, 3, 0,   // 0xb0-0xbf
+        2, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0xc0-0xcf
+        2, 2, 2, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,   // 0xd0-0xdf
+        2, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0xe0-0xef
+        2, 2, 2, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0    // 0xf0-0xff
     };
 
     /**
-     * Number of clock cycles required for each instruction
+     * Number of clock cycles required for each instruction when
+     * in NMOS mode.
      */
-    int[] instructionClocks = {
-        7, 6, 0, 0, 0, 3, 5, 0, 3, 2, 2, 0, 0, 4, 6, 0,
-        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,
-        6, 6, 0, 0, 3, 3, 5, 0, 4, 2, 2, 0, 4, 4, 6, 0,
-        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,
-        6, 6, 0, 0, 0, 3, 5, 0, 3, 2, 2, 0, 3, 4, 6, 0,
-        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,
-        6, 6, 0, 0, 0, 3, 5, 0, 4, 2, 2, 0, 5, 4, 6, 0,
-        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,
-        2, 6, 0, 0, 3, 3, 3, 0, 2, 0, 2, 0, 4, 4, 4, 0,
-        2, 6, 0, 0, 4, 4, 4, 0, 2, 5, 2, 0, 0, 5, 0, 0,
-        2, 6, 2, 0, 3, 3, 3, 0, 2, 2, 2, 0, 4, 4, 4, 0,
-        2, 5, 0, 0, 4, 4, 4, 0, 2, 4, 2, 0, 4, 4, 4, 0,
-        2, 6, 0, 0, 3, 3, 5, 0, 2, 2, 2, 0, 4, 4, 6, 0,
-        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,
-        2, 6, 0, 0, 3, 3, 5, 0, 2, 2, 2, 0, 4, 4, 6, 0,
-        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0
+    int[] instructionClocksNmos = {
+        7, 6, 0, 0, 0, 3, 5, 0, 3, 2, 2, 0, 0, 4, 6, 0,   // 0x00-0x0f
+        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x10-0x1f
+        6, 6, 0, 0, 3, 3, 5, 0, 4, 2, 2, 0, 4, 4, 6, 0,   // 0x20-0x2f
+        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x30-0x3f
+        6, 6, 0, 0, 0, 3, 5, 0, 3, 2, 2, 0, 3, 4, 6, 0,   // 0x40-0x4f
+        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x50-0x5f
+        6, 6, 0, 0, 0, 3, 5, 0, 4, 2, 2, 0, 5, 4, 6, 0,   // 0x60-0x6f
+        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x70-0x7f
+        2, 6, 0, 0, 3, 3, 3, 0, 2, 0, 2, 0, 4, 4, 4, 0,   // 0x80-0x8f
+        2, 6, 0, 0, 4, 4, 4, 0, 2, 5, 2, 0, 0, 5, 0, 0,   // 0x90-0x9f
+        2, 6, 2, 0, 3, 3, 3, 0, 2, 2, 2, 0, 4, 4, 4, 0,   // 0xa0-0xaf
+        2, 5, 0, 0, 4, 4, 4, 0, 2, 4, 2, 0, 4, 4, 4, 0,   // 0xb0-0xbf
+        2, 6, 0, 0, 3, 3, 5, 0, 2, 2, 2, 0, 4, 4, 6, 0,   // 0xc0-0xcf
+        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0xd0-0xdf
+        2, 6, 0, 0, 3, 3, 5, 0, 2, 2, 2, 0, 4, 4, 6, 0,   // 0xe0-0xef
+        2, 5, 0, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0    // 0xf0-0xff
+    };
+
+    /**
+     * Number of clock cycles required for each instruction when
+     * in CMOS mode
+     */
+    int[] instructionClocksCmos = {
+        7, 6, 0, 0, 0, 3, 5, 0, 3, 2, 2, 0, 0, 4, 6, 0,   // 0x00-0x0f
+        2, 5, 5, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x10-0x1f
+        6, 6, 0, 0, 3, 3, 5, 0, 4, 2, 2, 0, 4, 4, 6, 0,   // 0x20-0x2f
+        2, 5, 5, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x30-0x3f
+        6, 6, 0, 0, 0, 3, 5, 0, 3, 2, 2, 0, 3, 4, 6, 0,   // 0x40-0x4f
+        2, 5, 5, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x50-0x5f
+        6, 6, 0, 0, 0, 3, 5, 0, 4, 2, 2, 0, 5, 4, 6, 0,   // 0x60-0x6f
+        2, 5, 5, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0x70-0x7f
+        2, 6, 0, 0, 3, 3, 3, 0, 2, 0, 2, 0, 4, 4, 4, 0,   // 0x80-0x8f
+        2, 6, 5, 0, 4, 4, 4, 0, 2, 5, 2, 0, 0, 5, 0, 0,   // 0x90-0x9f
+        2, 6, 2, 0, 3, 3, 3, 0, 2, 2, 2, 0, 4, 4, 4, 0,   // 0xa0-0xaf
+        2, 5, 5, 0, 4, 4, 4, 0, 2, 4, 2, 0, 4, 4, 4, 0,   // 0xb0-0xbf
+        2, 6, 0, 0, 3, 3, 5, 0, 2, 2, 2, 0, 4, 4, 6, 0,   // 0xc0-0xcf
+        2, 5, 5, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0,   // 0xd0-0xdf
+        2, 6, 0, 0, 3, 3, 5, 0, 2, 2, 2, 0, 4, 4, 6, 0,   // 0xe0-0xef
+        2, 5, 5, 0, 0, 4, 6, 0, 2, 4, 0, 0, 0, 4, 7, 0    // 0xf0-0xff
     };
 
 }

src/main/java/com/loomcom/symon/Main.java

@@ -86,13 +86,16 @@ public class Main {
         
             final Simulator simulator = new Simulator(machineClass);
         
-            SwingUtilities.invokeLater(() -> {
-                try {
-                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-                    // Create the main UI window
-                    simulator.createAndShowUi();
-                } catch (Exception e) {
-                    e.printStackTrace();
+            SwingUtilities.invokeLater(new Runnable() {
+                @Override
+                public void run() {
+                    try {
+                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
+                        // Create the main UI window
+                        simulator.createAndShowUi();
+                    } catch (Exception e) {
+                        e.printStackTrace();
+                    }
                 }
             });
         

src/main/java/com/loomcom/symon/Simulator.java

@@ -119,7 +119,7 @@ public class Simulator {
     private JFileChooser fileChooser;
     private PreferencesDialog preferences;
 
-    private SortedSet<Integer> breakpoints;
+    private Breakpoints breakpoints;
 
     private final Object commandMonitorObject = new Object();
 
@@ -136,7 +136,7 @@ public class Simulator {
     private static final String[] STEPS = {"1", "5", "10", "20", "50", "100"};
 
     public Simulator(Class machineClass) throws Exception {
-        this.breakpoints = new TreeSet<>();
+        this.breakpoints = new Breakpoints(this);
 
         this.machine = (Machine) machineClass.getConstructors()[0].newInstance();
 
@@ -185,13 +185,16 @@ public class Simulator {
         JButton hardResetButton = new JButton("Hard Reset");
 
         stepCountBox = new JComboBox<>(STEPS);
-        stepCountBox.addActionListener(actionEvent -> {
-            try {
-                JComboBox cb = (JComboBox) actionEvent.getSource();
-                stepsPerClick = Integer.parseInt((String) cb.getSelectedItem());
-            } catch (NumberFormatException ex) {
-                stepsPerClick = 1;
-                stepCountBox.setSelectedIndex(0);
+        stepCountBox.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent actionEvent) {
+                try {
+                    JComboBox cb = (JComboBox) actionEvent.getSource();
+                    stepsPerClick = Integer.parseInt((String) cb.getSelectedItem());
+                } catch (NumberFormatException ex) {
+                    stepsPerClick = 1;
+                    stepCountBox.setSelectedIndex(0);
+                }
             }
         });
 
@@ -211,24 +214,38 @@ public class Simulator {
         // Bottom - buttons.
         mainWindow.getContentPane().add(buttonContainer, BorderLayout.PAGE_END);
 
-        runStopButton.addActionListener(actionEvent -> {
-            if (runLoop != null && runLoop.isRunning()) {
-                handleStop();
-            } else {
-                handleStart();
+        runStopButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent actionEvent) {
+                if (runLoop != null && runLoop.isRunning()) {
+                    Simulator.this.handleStop();
+                } else {
+                    Simulator.this.handleStart();
+                }
             }
         });
 
-        stepButton.addActionListener(actionEvent -> handleStep(stepsPerClick));
-
-        softResetButton.addActionListener(actionEvent -> {
-            // If this was a CTRL-click, do a hard reset.
-            handleReset(false);
+        stepButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent actionEvent) {
+                Simulator.this.handleStep(stepsPerClick);
+            }
         });
 
-        hardResetButton.addActionListener(actionEvent -> {
-            // If this was a CTRL-click, do a hard reset.
-            handleReset(true);
+        softResetButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent actionEvent) {
+                // If this was a CTRL-click, do a hard reset.
+                Simulator.this.handleReset(false);
+            }
+        });
+
+        hardResetButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent actionEvent) {
+                // If this was a CTRL-click, do a hard reset.
+                Simulator.this.handleReset(true);
+            }
         });
 
         mainWindow.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
@@ -400,13 +417,16 @@ public class Simulator {
             logger.debug("Starting main run loop.");
             isRunning = true;
 
-            SwingUtilities.invokeLater(() -> {
-                // Don't allow step while the simulator is running
-                stepButton.setEnabled(false);
-                stepCountBox.setEnabled(false);
-                menuBar.simulatorDidStart();
-                // Toggle the state of the run button
-                runStopButton.setText("Stop");
+            SwingUtilities.invokeLater(new Runnable() {
+                @Override
+                public void run() {
+                    // Don't allow step while the simulator is running
+                    stepButton.setEnabled(false);
+                    stepCountBox.setEnabled(false);
+                    menuBar.simulatorDidStart();
+                    // Toggle the state of the run button
+                    runStopButton.setText("Stop");
+                }
             });
 
             try {
@@ -417,17 +437,20 @@ public class Simulator {
                 logger.error("Exception in main simulator run thread. Exiting run.", ex);
             }
 
-            SwingUtilities.invokeLater(() -> {
-                statusPane.updateState();
-                memoryWindow.updateState();
-                runStopButton.setText("Run");
-                stepButton.setEnabled(true);
-                stepCountBox.setEnabled(true);
-                if (traceLog.isVisible()) {
-                    traceLog.refresh();
+            SwingUtilities.invokeLater(new Runnable() {
+                @Override
+                public void run() {
+                    statusPane.updateState();
+                    memoryWindow.updateState();
+                    runStopButton.setText("Run");
+                    stepButton.setEnabled(true);
+                    stepCountBox.setEnabled(true);
+                    if (traceLog.isVisible()) {
+                        traceLog.refresh();
+                    }
+                    menuBar.simulatorDidStop();
+                    traceLog.simulatorDidStop();
                 }
-                menuBar.simulatorDidStop();
-                traceLog.simulatorDidStop();
             });
 
             isRunning = false;
@@ -443,6 +466,10 @@ public class Simulator {
         }
     }
 
+    public String disassembleOpAtAddress(int address) throws MemoryAccessException {
+        return machine.getCpu().disassembleOpAtAddress(address);
+    }
+
     class LoadProgramAction extends AbstractAction {
         public LoadProgramAction() {
             super("Load Program...", null);
@@ -473,10 +500,17 @@ public class Simulator {
                                 program[i++] = dis.readByte();
                             }
 
-                            SwingUtilities.invokeLater(() -> console.reset());
-
                             // Now load the program at the starting address.
                             loadProgram(program, preferences.getProgramStartAddress());
+
+                            SwingUtilities.invokeLater(new Runnable() {
+                                @Override
+                                public void run() {
+                                    console.reset();
+                                    breakpoints.refresh();
+                                }
+                            });
+
                             // TODO: "Don't Show Again" checkbox
                             JOptionPane.showMessageDialog(mainWindow,
                                     "Loaded Successfully At " +
@@ -524,6 +558,9 @@ public class Simulator {
 
                         updateVisibleState();
 
+                        // Refresh breakpoints to show new memory contents.
+                        breakpoints.refresh();
+
                         logger.info("ROM File `{}' loaded at {}", romFile.getName(),
                                 String.format("0x%04X", machine.getRomBase()));
                         // TODO: "Don't Show Again" checkbox
@@ -612,9 +649,12 @@ public class Simulator {
         }
 
         public void actionPerformed(ActionEvent actionEvent) {
-            SwingUtilities.invokeLater(() -> {
-                console.setFont(new Font("Monospaced", Font.PLAIN, size));
-                mainWindow.pack();
+            SwingUtilities.invokeLater(new Runnable() {
+                @Override
+                public void run() {
+                    console.setFont(new Font("Monospaced", Font.PLAIN, size));
+                    mainWindow.pack();
+                }
             });
         }
     }
@@ -878,12 +918,15 @@ public class Simulator {
 
     private void updateVisibleState() {
         // Immediately update the UI.
-        SwingUtilities.invokeLater(() -> {
-            // Now update the state
-            statusPane.updateState();
-            memoryWindow.updateState();
-            if (traceLog.shouldUpdate()) {
-                traceLog.refresh();
+        SwingUtilities.invokeLater(new Runnable() {
+            @Override
+            public void run() {
+                // Now update the state
+                statusPane.updateState();
+                memoryWindow.updateState();
+                if (traceLog.shouldUpdate()) {
+                    traceLog.refresh();
+                }
             }
         });
     }

src/main/java/com/loomcom/symon/devices/Device.java

@@ -115,7 +115,9 @@ public abstract class Device implements Comparable<Device> {
     }
 
     public void notifyListeners() {
-        deviceChangeListeners.forEach(DeviceChangeListener::deviceStateChanged);
+        for (DeviceChangeListener listener : deviceChangeListeners) {
+            listener.deviceStateChanged();
+        }
     }
 
     /**

src/main/java/com/loomcom/symon/devices/SdController.java

@@ -27,7 +27,6 @@ package com.loomcom.symon.devices;
 
 import com.loomcom.symon.exceptions.MemoryAccessException;
 import com.loomcom.symon.exceptions.MemoryRangeException;
-import jdk.nashorn.internal.ir.annotations.Ignore;
 
 import java.io.File;
 import java.io.FileInputStream;

src/main/java/com/loomcom/symon/ui/BreakpointsWindow.java

@@ -23,16 +23,18 @@
 
 package com.loomcom.symon.ui;
 
-import com.loomcom.symon.util.HexUtil;
+import com.loomcom.symon.Breakpoints;
+import com.loomcom.symon.util.Utils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import javax.swing.*;
 import javax.swing.border.EmptyBorder;
+import javax.swing.event.ListSelectionEvent;
+import javax.swing.event.ListSelectionListener;
 import java.awt.*;
+import java.awt.event.ActionEvent;
 import java.awt.event.ActionListener;
-import java.util.ArrayList;
-import java.util.SortedSet;
 
 /**
  * Simple window to enter breakpoints.
@@ -45,45 +47,9 @@ public class BreakpointsWindow extends JFrame {
     private static final String EMPTY_STRING = "";
 
     private JFrame mainWindow;
-    private SortedSet<Integer> breakpoints;
+    private Breakpoints breakpoints;
 
-    /**
-     * Simple ListModel to back the list of breakpoints.
-     */
-    private class BreakpointsListModel extends AbstractListModel<String> {
-        private SortedSet<Integer> breakpoints;
-
-        public BreakpointsListModel(SortedSet<Integer> breakpoints) {
-            this.breakpoints = breakpoints;
-        }
-
-        @Override
-        public int getSize() {
-            return breakpoints.size();
-        }
-
-        @Override
-        public String getElementAt(int index) {
-            ArrayList<Integer> values = new ArrayList<>(breakpoints);
-            return "$" + HexUtil.wordToHex(values.get(index));
-        }
-
-        public void addElement(Integer breakpoint) {
-            breakpoints.add(breakpoint);
-            ArrayList<Integer> values = new ArrayList<>(breakpoints);
-            int index = values.indexOf(breakpoint);
-            fireIntervalAdded(this, index, index);
-        }
-
-        public void removeElement(int index) {
-            ArrayList<Integer> values = new ArrayList<>(breakpoints);
-            Integer breakpoint = values.get(index);
-            breakpoints.remove(breakpoint);
-            fireIntervalRemoved(this, index, index);
-        }
-    }
-
-    public BreakpointsWindow(SortedSet<Integer> breakpoints,
+    public BreakpointsWindow(Breakpoints breakpoints,
                              JFrame mainWindow) {
         this.breakpoints = breakpoints;
         this.mainWindow = mainWindow;
@@ -99,65 +65,72 @@ public class BreakpointsWindow extends JFrame {
         breakpointsPanel.setLayout(new BorderLayout());
         breakpointsPanel.setBorder(new EmptyBorder(10, 10, 10, 10));
 
-        JButton addButton = new JButton("Add");
-        JButton removeButton = new JButton("Del");
+        final JButton addButton = new JButton("Add");
+        final JButton removeButton = new JButton("Del");
         removeButton.setEnabled(false);
 
-        JTextField addTextField = new JTextField(5);
+        final JTextField addTextField = new JTextField(4);
 
-        BreakpointsListModel listModel = new BreakpointsListModel(breakpoints);
-        JList<String> breakpointsList = new JList<>(listModel);
-        breakpointsList.setFont(new Font("Monospace", Font.PLAIN, 14));
-        breakpointsList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
+        final JTable breakpointsTable = new JTable(breakpoints);
+        breakpointsTable.setShowGrid(true);
+        breakpointsTable.setGridColor(Color.LIGHT_GRAY);
+        breakpointsTable.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
+        breakpointsTable.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
+            @Override
+            public void valueChanged(ListSelectionEvent e) {
+                if (e.getFirstIndex() > -1) {
+                    removeButton.setEnabled(true);
+                } else {
+                    removeButton.setEnabled(false);
+                }
+            }
+        });
 
-        JScrollPane scrollPane = new JScrollPane(breakpointsList);
+        JScrollPane scrollPane = new JScrollPane(breakpointsTable);
         scrollPane.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
         scrollPane.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
 
         breakpointsPanel.add(scrollPane, BorderLayout.CENTER);
 
+        ActionListener addBreakpointListener = new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                int value;
 
-        breakpointsList.addListSelectionListener(le -> {
-            int idx = breakpointsList.getSelectedIndex();
+                String newBreakpoint = addTextField.getText();
 
-            if (idx == -1) {
-                removeButton.setEnabled(false);
-            } else {
-                removeButton.setEnabled(true);
+                if (newBreakpoint == null || newBreakpoint.isEmpty()) {
+                    return;
+                }
+
+                try {
+                    value = (Integer.parseInt(addTextField.getText(), 16) & 0xffff);
+                } catch (NumberFormatException ex) {
+                    logger.warn("Can't parse page number {}", newBreakpoint);
+                    return;
+                }
+
+                if (value < 0) {
+                    return;
+                }
+
+                breakpoints.addBreakpoint(value);
+
+                logger.debug("Added breakpoint ${}", Utils.wordToHex(value));
+
+                addTextField.setText(EMPTY_STRING);
             }
-        });
-
-        ActionListener addBreakpointListener = e -> {
-            int value = -1;
-
-            String newBreakpoint = addTextField.getText();
-
-            if (newBreakpoint == null || newBreakpoint.isEmpty()) {
-                return;
-            }
-
-            try {
-                value = (Integer.parseInt(addTextField.getText(), 16) & 0xffff);
-            } catch (NumberFormatException ex) {
-                logger.warn("Can't parse page number {}", newBreakpoint);
-                return;
-            }
-
-            if (value < 0) {
-                return;
-            }
-
-            listModel.addElement(value);
-
-            logger.debug("Added breakpoint ${}", HexUtil.wordToHex(value));
-
-            addTextField.setText(EMPTY_STRING);
         };
 
         addButton.addActionListener(addBreakpointListener);
         addTextField.addActionListener(addBreakpointListener);
 
-        removeButton.addActionListener(e -> listModel.removeElement(breakpointsList.getSelectedIndex()));
+        removeButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                breakpoints.removeBreakpointAtIndex(breakpointsTable.getSelectedRow());
+            }
+        });
 
         controlPanel.add(addTextField);
         controlPanel.add(addButton);

src/main/java/com/loomcom/symon/ui/MemoryWindow.java

@@ -25,7 +25,7 @@ package com.loomcom.symon.ui;
 
 import com.loomcom.symon.Bus;
 import com.loomcom.symon.exceptions.MemoryAccessException;
-import com.loomcom.symon.util.HexUtil;
+import com.loomcom.symon.util.Utils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -107,7 +107,7 @@ public class MemoryWindow extends JFrame implements ActionListener {
 
         previousPageButton.setEnabled(pageNumber > 0x00);
         nextPageButton.setEnabled(pageNumber < 0xff);
-        pageNumberTextField.setText(HexUtil.byteToHex(pageNumber));
+        pageNumberTextField.setText(Utils.byteToHex(pageNumber));
     }
 
     /**
@@ -328,13 +328,13 @@ public class MemoryWindow extends JFrame implements ActionListener {
         public Object getValueAt(int row, int column) {
             try {
                 if (column == 0) {
-                    return HexUtil.wordToHex(fullAddress(row, 1));
+                    return Utils.wordToHex(fullAddress(row, 1));
                 } else if (column < 9) {
                     // Display hex value of the data
-                    return HexUtil.byteToHex(bus.read(fullAddress(row, column)));
+                    return Utils.byteToHex(bus.read(fullAddress(row, column)));
                 } else {
                     // Display the ASCII equivalent (if printable)
-                    return HexUtil.byteToAscii(bus.read(fullAddress(row, column - 8)));
+                    return Utils.byteToAscii(bus.read(fullAddress(row, column - 8)));
                 }
             } catch (MemoryAccessException ex) {
                 return "??";

src/main/java/com/loomcom/symon/ui/PreferencesDialog.java

@@ -97,19 +97,25 @@ public class PreferencesDialog extends Observable implements Preferences {
         JButton applyButton = new JButton("Apply");
         JButton cancelButton = new JButton("Cancel");
 
-        cancelButton.addActionListener(actionEvent -> {
-            updateUi();
-            dialog.setVisible(false);
+        cancelButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent actionEvent) {
+                PreferencesDialog.this.updateUi();
+                dialog.setVisible(false);
+            }
         });
 
-        applyButton.addActionListener(actionEvent -> {
-            haltOnBreak = haltOnBreakCheckBox.isSelected();
-            programLoadAddress = hexToInt(programLoadAddressField.getText());
-            updateUi();
-            // TODO: Actually check to see if values have changed, don't assume.
-            setChanged();
-            PreferencesDialog.this.notifyObservers();
-            dialog.setVisible(false);
+        applyButton.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent actionEvent) {
+                haltOnBreak = haltOnBreakCheckBox.isSelected();
+                programLoadAddress = PreferencesDialog.this.hexToInt(programLoadAddressField.getText());
+                PreferencesDialog.this.updateUi();
+                // TODO: Actually check to see if values have changed, don't assume.
+                PreferencesDialog.this.setChanged();
+                PreferencesDialog.this.notifyObservers();
+                dialog.setVisible(false);
+            }
         });
 
         buttonsContainer.add(applyButton);

src/main/java/com/loomcom/symon/ui/StatusPanel.java

@@ -24,6 +24,7 @@
 package com.loomcom.symon.ui;
 
 import com.loomcom.symon.Cpu;
+import com.loomcom.symon.CpuState;
 import com.loomcom.symon.machines.Machine;
 
 import javax.swing.*;
@@ -163,59 +164,74 @@ public class StatusPanel extends JPanel {
         yField = makeTextField(SMALL_TEXT_FIELD_SIZE, true);
 
         // Make fields editable
-        pcField.addActionListener(e -> {
-            try {
-                int newVal = getHexVal(pcField) & 0xffff;
-                machine.getCpu().setProgramCounter(newVal);
-            } catch (Exception ex) {
-                // Swallow exception
-            }
+        pcField.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                try {
+                    int newVal = StatusPanel.this.getHexVal(pcField) & 0xffff;
+                    machine.getCpu().setProgramCounter(newVal);
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        spField.addActionListener(e -> {
-            try {
-                int newVal = getHexVal(spField) & 0xff;
-                machine.getCpu().setStackPointer(newVal);
-            } catch (Exception ex) {
-                // Swallow exception
-            }
+        spField.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                try {
+                    int newVal = StatusPanel.this.getHexVal(spField) & 0xff;
+                    machine.getCpu().setStackPointer(newVal);
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        aField.addActionListener(e -> {
-            try {
-                int newVal = getHexVal(aField) & 0xff;
-                machine.getCpu().setAccumulator(newVal);
-            } catch (Exception ex) {
-                // Swallow exception
-            }
+        aField.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                try {
+                    int newVal = StatusPanel.this.getHexVal(aField) & 0xff;
+                    machine.getCpu().setAccumulator(newVal);
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        xField.addActionListener(e -> {
-            try {
-                int newVal = getHexVal(xField) & 0xff;
-                machine.getCpu().setXRegister(newVal);
-            } catch (Exception ex) {
-                // Swallow exception
-            }
+        xField.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                try {
+                    int newVal = StatusPanel.this.getHexVal(xField) & 0xff;
+                    machine.getCpu().setXRegister(newVal);
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        yField.addActionListener(e -> {
-            try {
-                int newVal = getHexVal(yField) & 0xff;
-                machine.getCpu().setYRegister(newVal);
-            } catch (Exception ex) {
-                // Swallow exception
-            }
+        yField.addActionListener(new ActionListener() {
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                try {
+                    int newVal = StatusPanel.this.getHexVal(yField) & 0xff;
+                    machine.getCpu().setYRegister(newVal);
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
         constraints.anchor = GridBagConstraints.LINE_START;
@@ -277,7 +293,7 @@ public class StatusPanel extends JPanel {
      */
     public void updateState() {
         Cpu cpu = machine.getCpu();
-        Cpu.CpuState cpuState = cpu.getCpuState();
+        CpuState cpuState = cpu.getCpuState();
 
         // Update the Processor Status Flag display
         int status = cpuState.getStatusFlag();
@@ -293,7 +309,7 @@ public class StatusPanel extends JPanel {
         // Update the register and address displays
 
         // We always want to show the NEXT instruction that will be executed
-        opcodeField.setText(cpu.getCpuState().disassembleNextOp());
+        opcodeField.setText(cpu.disassembleNextOp());
         pcField.setText(cpu.getProgramCounterStatus());
         spField.setText(cpu.getStackPointerStatus());
         aField.setText(cpu.getAccumulatorStatus());

src/main/java/com/loomcom/symon/ui/TraceLog.java

@@ -24,7 +24,7 @@
 
 package com.loomcom.symon.ui;
 
-import com.loomcom.symon.Cpu;
+import com.loomcom.symon.CpuState;
 import com.loomcom.symon.util.FifoRingBuffer;
 
 import javax.swing.*;
@@ -36,7 +36,7 @@ import java.awt.*;
  */
 public class TraceLog extends JFrame {
 
-    private final FifoRingBuffer<Cpu.CpuState> traceLog;
+    private final FifoRingBuffer<CpuState> traceLog;
     private final JTextArea                    traceLogTextArea;
 
     private static final Dimension MIN_SIZE       = new Dimension(320, 200);
@@ -71,7 +71,7 @@ public class TraceLog extends JFrame {
         StringBuilder logString = new StringBuilder();        
         
         synchronized(traceLog) {
-            for (Cpu.CpuState state : traceLog) {
+            for (CpuState state : traceLog) {
                 logString.append(state.toTraceEvent());
             }
         }
@@ -99,9 +99,9 @@ public class TraceLog extends JFrame {
      *
      * @param state The CPU State to append.
      */
-    public void append(Cpu.CpuState state) {
+    public void append(CpuState state) {
         synchronized(traceLog) {
-            traceLog.push(new Cpu.CpuState(state));
+            traceLog.push(new CpuState(state));
         }
     }
 

src/main/java/com/loomcom/symon/ui/VideoWindow.java

@@ -122,10 +122,13 @@ public class VideoWindow extends JFrame implements DeviceChangeListener {
      */
     private class CursorBlinker implements Runnable {
         public void run() {
-            SwingUtilities.invokeLater(() -> {
-                if (cursorBlinkRate > 0) {
-                    hideCursor = !hideCursor;
-                    repaint();
+            SwingUtilities.invokeLater(new Runnable() {
+                @Override
+                public void run() {
+                    if (cursorBlinkRate > 0) {
+                        hideCursor = !hideCursor;
+                        VideoWindow.this.repaint();
+                    }
                 }
             });
         }

src/main/java/com/loomcom/symon/util/Utils.java

@@ -24,24 +24,9 @@
 package com.loomcom.symon.util;
 
 /**
- * Hex String Utilities.
- *
- * <p/>
- *
- * But why? Java, after all, has a number of ways to convert an integer into a hex string,
- * so it may look absurd to go to the trouble of writing yet another conversion! The answer is
- * performance.
- *
- * <p/>
- *
- * The most convenient way to get a formatted hex value from an integer is with the <code>String.format</code>
- * method, but this turns out to be extremely inefficient. Formatting a million integers
- * with <code>String.format</code> takes something like 1600ms. Formatting the same number of integers
- * with <code>HexUtil</code> takes only 160ms. This is on par with <code>Integer.toHexString</code>,
- * but also gives the desired padding.
- *
+ * Various Utilities
  */
-public class HexUtil {
+public class Utils {
 
     static final String NON_PRINTABLE = ".";
 
@@ -93,6 +78,7 @@ public class HexUtil {
 
     /**
      * Very fast 8-bit int to ASCII conversion.
+     *
      * @param val The value of an ASCII character.
      * @return A string representing the ASCII character.
      */
@@ -123,4 +109,11 @@ public class HexUtil {
     public static String wordToHex(int val) {
         return HEX_CONSTANTS[(val >> 8) & 0xff] + HEX_CONSTANTS[val & 0xff];
     }
+
+    /**
+     * Given two bytes, return an address.
+     */
+    public static int address(int lowByte, int hiByte) {
+        return ((hiByte << 8) | lowByte) & 0xffff;
+    }
 }

src/test/java/com/loomcom/symon/CpuImpliedModeTest.java

@@ -117,9 +117,22 @@ public class CpuImpliedModeTest {
     }
 
     @Test
-    public void test_BRK_HonorsIrqDisableFlag() throws MemoryAccessException {
+    public void test_BRK_IgnoresIrqDisableFlag() throws MemoryAccessException {
         cpu.setIrqDisableFlag();
 
+        cpu.setCarryFlag();
+        cpu.setOverflowFlag();
+        assertEquals(0x20 | Cpu.P_CARRY | Cpu.P_OVERFLOW | Cpu.P_IRQ_DISABLE,
+                     cpu.getProcessorStatus());
+        assertEquals(0x00, cpu.stackPeek());
+        assertFalse(cpu.getBreakFlag());
+        assertEquals(0x0200, cpu.getProgramCounter());
+        assertEquals(0xff, cpu.getStackPointer());
+        
+        // Set the IRQ vector
+        bus.write(0xffff, 0x12);
+        bus.write(0xfffe, 0x34);
+
         bus.loadProgram(0xea,
                         0xea,
                         0xea,
@@ -131,23 +144,26 @@ public class CpuImpliedModeTest {
 
         assertEquals(0x203, cpu.getProgramCounter());
 
-        // Triggers the BRK, which should do nothing because
-        // of the Interrupt Disable flag
+        // Triggers the BRK
         cpu.step();
 
-        // Reset to original contents of PC
-        assertEquals(0x0204, cpu.getProgramCounter());
-        // Empty stack
-        assertEquals(0xff, cpu.getStackPointer());
 
-        cpu.step(2); // Two more NOPs
+        // Was at PC = 0x204.  PC+1 should now be on the stack
+        assertEquals(0x02, bus.read(0x1ff)); // PC high byte
+        assertEquals(0x05, bus.read(0x1fe)); // PC low byte
+        assertEquals(0x20 | Cpu.P_CARRY | Cpu.P_OVERFLOW | Cpu.P_BREAK | Cpu.P_IRQ_DISABLE,
+                     bus.read(0x1fd));       // Processor Status, with B set
 
-        // Reset to original contents of PC
-        assertEquals(0x0206, cpu.getProgramCounter());
-        // Empty stack
-        assertEquals(0xff, cpu.getStackPointer());
+        // Interrupt vector held 0x1234, so we should be there.
+        assertEquals(0x1234, cpu.getProgramCounter());
+        assertEquals(0xfc, cpu.getStackPointer());
+
+        // B and I flags should have been set on P
+        assertEquals(0x20 | Cpu.P_CARRY | Cpu.P_OVERFLOW | Cpu.P_BREAK | Cpu.P_IRQ_DISABLE,
+                     cpu.getProcessorStatus());
     }
 
+
     /* CLC - Clear Carry Flag - $18 */
     @Test
     public void test_CLC() throws MemoryAccessException {

src/test/java/com/loomcom/symon/CpuIndirectIndexedModeTest.java

@@ -25,18 +25,10 @@ public class CpuIndirectIndexedModeTest {
         bus.write(0xfffd, (Bus.DEFAULT_LOAD_ADDRESS & 0xff00) >>> 8);
 
         cpu.reset();
-        // Assert initial state
-        assertEquals(0, cpu.getAccumulator());
-        assertEquals(0, cpu.getXRegister());
-        assertEquals(0, cpu.getYRegister());
-        assertEquals(0x200, cpu.getProgramCounter());
-        assertEquals(0xff, cpu.getStackPointer());
-        assertEquals(0x20, cpu.getProcessorStatus());
     }
 
     @Test
     public void test_LDA() throws Exception {
-        assertEquals(cpu.toString(), 0x00, cpu.getAccumulator());
         bus.write(0x0014, 0x00);
         bus.write(0x0015, 0xd8);
         bus.write(0xd828, 0x03);

src/test/java/com/loomcom/symon/CpuIndirectModeTest.java

@@ -3,15 +3,19 @@ package com.loomcom.symon;
 import com.loomcom.symon.devices.Memory;
 import com.loomcom.symon.exceptions.MemoryAccessException;
 
-import junit.framework.TestCase;
+import org.junit.Before;
+import org.junit.Test;
 
-public class CpuIndirectModeTest extends TestCase {
+import static org.junit.Assert.assertEquals;
+
+public class CpuIndirectModeTest {
 
     protected Cpu    cpu;
     protected Bus    bus;
     protected Memory mem;
 
-    protected void setUp() throws Exception {
+    @Before
+    public void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
         this.mem = new Memory(0x0000, 0xffff);
@@ -41,6 +45,7 @@ public class CpuIndirectModeTest extends TestCase {
 
     /* JMP - Jump - $6c */
 
+    @Test
     public void test_JMP_notOnPageBoundary() throws MemoryAccessException {
         bus.write(0x3400, 0x00);
         bus.write(0x3401, 0x54);
@@ -51,6 +56,7 @@ public class CpuIndirectModeTest extends TestCase {
         assertEquals(0x20, cpu.getProcessorStatus());
     }
 
+    @Test
     public void test_JMP_with_ROR_Bug() throws MemoryAccessException {
         cpu.setBehavior(Cpu.CpuBehavior.NMOS_WITH_ROR_BUG);
         bus.write(0x3400, 0x22);
@@ -63,8 +69,9 @@ public class CpuIndirectModeTest extends TestCase {
         assertEquals(0x20, cpu.getProcessorStatus());
     }
 
+    @Test
     public void test_JMP_withIndirectBug() throws MemoryAccessException {
-        cpu.setBehavior(Cpu.CpuBehavior.NMOS_WITH_INDIRECT_JMP_BUG);
+        cpu.setBehavior(Cpu.CpuBehavior.NMOS_6502);
         bus.write(0x3400, 0x22);
         bus.write(0x34ff, 0x00);
         bus.write(0x3500, 0x54);
@@ -75,8 +82,9 @@ public class CpuIndirectModeTest extends TestCase {
         assertEquals(0x20, cpu.getProcessorStatus());
     }
 
+    @Test
     public void test_JMP_withOutIndirectBug() throws MemoryAccessException {
-        cpu.setBehavior(Cpu.CpuBehavior.NMOS_WITHOUT_INDIRECT_JMP_BUG);
+        cpu.setBehavior(Cpu.CpuBehavior.CMOS_6502);
         bus.write(0x3400, 0x22);
         bus.write(0x34ff, 0x00);
         bus.write(0x3500, 0x54);
@@ -87,8 +95,9 @@ public class CpuIndirectModeTest extends TestCase {
         assertEquals(0x20, cpu.getProcessorStatus());
     }
 
+    @Test
     public void test_JMP_cmos() throws MemoryAccessException {
-        cpu.setBehavior(Cpu.CpuBehavior.CMOS);
+        cpu.setBehavior(Cpu.CpuBehavior.CMOS_6502);
         bus.write(0x3400, 0x22);
         bus.write(0x34ff, 0x00);
         bus.write(0x3500, 0x54);

src/test/java/com/loomcom/symon/CpuIndirectXModeTest.java

@@ -3,14 +3,21 @@ package com.loomcom.symon;
 import com.loomcom.symon.devices.Memory;
 import com.loomcom.symon.exceptions.MemoryAccessException;
 import junit.framework.TestCase;
+import org.junit.Before;
+import org.junit.Test;
 
-public class CpuIndirectXModeTest extends TestCase {
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class CpuIndirectXModeTest {
 
     protected Cpu    cpu;
     protected Bus    bus;
     protected Memory mem;
 
-    protected void setUp() throws Exception {
+    @Before
+    public void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
         this.mem = new Memory(0x0000, 0xffff);
@@ -47,7 +54,7 @@ public class CpuIndirectXModeTest extends TestCase {
     */
 
     /* ORA - Logical Inclusive OR - $1d */
-
+    @Test
     public void test_ORA() throws MemoryAccessException {
         // Set some initial values in memory
         bus.write(0x2c30, 0x00);
@@ -93,7 +100,7 @@ public class CpuIndirectXModeTest extends TestCase {
     }
 
     /* AND - Logical AND - $3d */
-
+    @Test
     public void test_AND() throws MemoryAccessException {
         bus.write(0x1a30, 0x00);
         bus.write(0x1a31, 0x11);
@@ -153,7 +160,7 @@ public class CpuIndirectXModeTest extends TestCase {
     }
 
     /* EOR - Exclusive OR - $5d */
-
+    @Test
     public void test_EOR() throws MemoryAccessException {
         bus.write(0xab40, 0x00);
         bus.write(0xab41, 0xff);
@@ -162,7 +169,7 @@ public class CpuIndirectXModeTest extends TestCase {
 
         cpu.setXRegister(0x30);
 
-        bus.loadProgram(0xa9, 0x88,         // LDA #$88
+        bus.loadProgram(0xa9, 0x88,        // LDA #$88
                         0x5d, 0x10, 0xab,  // EOR $ab10,X
                         0x5d, 0x11, 0xab,  // EOR $ab11,X
                         0x5d, 0x12, 0xab,  // EOR $ab12,X
@@ -189,7 +196,7 @@ public class CpuIndirectXModeTest extends TestCase {
     }
 
     /* ADC - Add with Carry - $7d */
-
+    @Test
     public void test_ADC() throws MemoryAccessException {
         bus.write(0xab40, 0x01);
         bus.write(0xab41, 0xff);
@@ -290,6 +297,7 @@ public class CpuIndirectXModeTest extends TestCase {
         assertTrue(cpu.getCarryFlag());
     }
 
+    @Test
     public void test_ADC_IncludesCarry() throws MemoryAccessException {
         bus.write(0xab40, 0x01);
 
@@ -307,6 +315,7 @@ public class CpuIndirectXModeTest extends TestCase {
         assertFalse(cpu.getCarryFlag());
     }
 
+    @Test
     public void test_ADC_DecimalMode() throws MemoryAccessException {
         bus.write(0xab40, 0x01);
         bus.write(0xab41, 0x99);
@@ -404,7 +413,7 @@ public class CpuIndirectXModeTest extends TestCase {
     }
 
     /* STA - Store Accumulator - $9d */
-
+    @Test
     public void test_STA() throws MemoryAccessException {
         cpu.setXRegister(0x30);
 
@@ -438,7 +447,7 @@ public class CpuIndirectXModeTest extends TestCase {
     }
 
     /* LDA - Load Accumulator - $bd */
-
+    @Test
     public void test_LDA() throws MemoryAccessException {
         bus.write(0xab42, 0x00);
         bus.write(0xab43, 0x0f);
@@ -467,7 +476,7 @@ public class CpuIndirectXModeTest extends TestCase {
     }
 
     /* CMP - Compare Accumulator - $dd */
-
+    @Test
     public void test_CMP() throws MemoryAccessException {
         bus.write(0xab40, 0x00);
         bus.write(0xab41, 0x80);
@@ -498,7 +507,7 @@ public class CpuIndirectXModeTest extends TestCase {
     }
 
     /* SBC - Subtract with Carry - $fd */
-
+    @Test
     public void test_SBC() throws MemoryAccessException {
         bus.write(0xab40, 0x01);
 
@@ -557,6 +566,7 @@ public class CpuIndirectXModeTest extends TestCase {
         assertTrue(cpu.getCarryFlag());
     }
 
+    @Test
     public void test_SBC_IncludesNotOfCarry() throws MemoryAccessException {
         bus.write(0xab40, 0x01);
 
@@ -602,6 +612,7 @@ public class CpuIndirectXModeTest extends TestCase {
 
     }
 
+    @Test
     public void test_SBC_DecimalMode() throws MemoryAccessException {
         bus.write(0xab40, 0x01);
         bus.write(0xab50, 0x11);

src/test/java/com/loomcom/symon/CpuTest.java

@@ -1,5 +1,6 @@
 package com.loomcom.symon;
 
+import com.loomcom.symon.util.Utils;
 import junit.framework.*;
 
 import com.loomcom.symon.devices.*;
@@ -240,6 +241,7 @@ public class CpuTest extends TestCase {
 
     public void testSetProcessorStatus() {
         // Default
+
         assertFalse(cpu.getZeroFlag());
         assertFalse(cpu.getZeroFlag());
         assertFalse(cpu.getIrqDisableFlag());
@@ -383,6 +385,41 @@ public class CpuTest extends TestCase {
         assertFalse(cpu.getCpuState().irqAsserted);
     }
 
+    public void testIrqDoesNotSetBRK() throws Exception {
+        // Ensure the IRQ disable flag is cleared
+        cpu.clearIrqDisableFlag();
+
+        // Set the IRQ vector
+        bus.write(0xffff, 0x12);
+        bus.write(0xfffe, 0x34);
+
+        // Create an IRQ handler at 0x1234
+        cpu.setProgramCounter(0x1234);
+        bus.loadProgram(0xa9, 0x33,  // LDA #$33
+                        0x69, 0x01); // ADC #$01
+
+        cpu.setProgramCounter(0x0200);
+        // Create a little program at 0x0200
+        bus.loadProgram(0x18,        // CLC
+                        0xa9, 0x01,  // LDA #$00
+                        0x69, 0x01); // ADC #$01
+
+        cpu.step();
+        assertEquals(0x0201, cpu.getProgramCounter()); // First instruction executed.
+        assertEquals(0x00, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x0203, cpu.getProgramCounter());
+        assertEquals(0x01, cpu.getAccumulator());
+
+        cpu.assertIrq();
+
+        cpu.step();
+        assertTrue(cpu.getIrqDisableFlag()); // Should have been set by the IRQ
+        assertFalse(cpu.getBreakFlag());
+
+    }
+
     public void testIrqHonorsIrqDisabledFlag() throws Exception {
         // Ensure the IRQ disable flag is set
         cpu.setIrqDisableFlag();
@@ -497,6 +534,37 @@ public class CpuTest extends TestCase {
         assertFalse(cpu.getCpuState().nmiAsserted);
     }
 
+    public void testNmiDoesNotSetBRK() throws Exception {
+        // Set the NMI vector to 0x1000
+        bus.write(0xfffb, 0x10);
+        bus.write(0xfffa, 0x00);
+
+        // Create an NMI handler at 0x1000
+        cpu.setProgramCounter(0x1000);
+        bus.loadProgram(0xa9, 0x33,  // LDA #$33
+                        0x69, 0x01); // ADC #$01
+
+        // Create a little program at 0x0200
+        cpu.setProgramCounter(0x0200);
+        bus.loadProgram(0x18,        // CLC
+                        0xa9, 0x01,  // LDA #$00
+                        0x69, 0x01); // ADC #$01
+
+        cpu.step();
+        assertEquals(0x0201, cpu.getProgramCounter()); // First instruction executed.
+        assertEquals(0x00, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x0203, cpu.getProgramCounter());
+        assertEquals(0x01, cpu.getAccumulator());
+
+        cpu.assertNmi();
+
+        cpu.step();
+        assertFalse(cpu.getBreakFlag());
+
+}
+
     public void testNmiIgnoresIrqDisableFlag() throws Exception {
         // Set the IRQ disable flag, which should be ignored by the NMI
         cpu.setIrqDisableFlag();
@@ -537,11 +605,11 @@ public class CpuTest extends TestCase {
 
 
     public void testAddress() {
-        assertEquals(0xf1ea, cpu.address(0xea, 0xf1));
-        assertEquals(0x00ea, cpu.address(0xea, 0x00));
-        assertEquals(0xf100, cpu.address(0x00, 0xf1));
-        assertEquals(0x1234, cpu.address(0x34, 0x12));
-        assertEquals(0xffff, cpu.address(0xff, 0xff));
+        assertEquals(0xf1ea, Utils.address(0xea, 0xf1));
+        assertEquals(0x00ea, Utils.address(0xea, 0x00));
+        assertEquals(0xf100, Utils.address(0x00, 0xf1));
+        assertEquals(0x1234, Utils.address(0x34, 0x12));
+        assertEquals(0xffff, Utils.address(0xff, 0xff));
     }
 
     public void testZpxAddress() {

src/test/java/com/loomcom/symon/CpuZeroPageIndirectTest.java

@@ -0,0 +1,329 @@
+package com.loomcom.symon;
+
+import com.loomcom.symon.devices.Memory;
+import org.junit.Test;
+
+import static junit.framework.TestCase.assertFalse;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Test for Zero Page Indirect addressing mode, found on some instructions
+ * in the 65C02 and 65816
+ */
+public class CpuZeroPageIndirectTest {
+    protected Cpu    cpu;
+    protected Bus    bus;
+    protected Memory mem;
+
+    private void makeCmosCpu() throws Exception {
+        makeCpu(InstructionTable.CpuBehavior.CMOS_6502);
+    }
+
+    private void makeNmosCpu() throws Exception {
+        makeCpu(InstructionTable.CpuBehavior.NMOS_6502);
+    }
+
+    private void makeCpu(InstructionTable.CpuBehavior behavior) throws Exception {
+        this.cpu = new Cpu(behavior);
+        this.bus = new Bus(0x0000, 0xffff);
+        this.mem = new Memory(0x0000, 0xffff);
+        bus.addCpu(cpu);
+        bus.addDevice(mem);
+
+        // Load the reset vector.
+        bus.write(0xfffc, Bus.DEFAULT_LOAD_ADDRESS & 0x00ff);
+        bus.write(0xfffd, (Bus.DEFAULT_LOAD_ADDRESS & 0xff00) >>> 8);
+
+        cpu.reset();
+    }
+
+    @Test
+    public void test_ora() throws Exception {
+        makeCmosCpu();
+
+        // Set some initial values in zero page.
+        bus.write(0x30, 0x00);
+        bus.write(0x31, 0x10);
+
+        bus.write(0x40, 0x01);
+        bus.write(0x41, 0x10);
+
+        bus.write(0x50, 0x02);
+        bus.write(0x51, 0x10);
+
+        bus.write(0x60, 0x03);
+        bus.write(0x61, 0x10);
+
+        bus.write(0x1000, 0x11);
+        bus.write(0x1001, 0x22);
+        bus.write(0x1002, 0x44);
+        bus.write(0x1003, 0x88);
+
+        bus.loadProgram(0x12, 0x30,  // ORA ($30)
+                        0x12, 0x40,  // ORA ($40)
+                        0x12, 0x50,  // ORA ($50)
+                        0x12, 0x60); // ORA ($60)
+
+
+        assertEquals(0x00, cpu.getAccumulator());
+
+        // 0x00 | 0x11 = 0x11
+        cpu.step();
+        assertEquals(0x11, cpu.getAccumulator());
+        assertFalse(cpu.getZeroFlag());
+        assertFalse(cpu.getNegativeFlag());
+
+        // 0x11 | 0x22 = 0x33
+        cpu.step();
+        assertEquals(0x33, cpu.getAccumulator());
+        assertFalse(cpu.getZeroFlag());
+        assertFalse(cpu.getNegativeFlag());
+
+        // 0x33 | 0x44 = 0x77
+        cpu.step();
+        assertEquals(0x77, cpu.getAccumulator());
+        assertFalse(cpu.getZeroFlag());
+        assertFalse(cpu.getNegativeFlag());
+
+        // 0x77 | 0x88 = 0xff
+        cpu.step();
+        assertEquals(0xff, cpu.getAccumulator());
+        assertFalse(cpu.getZeroFlag());
+        assertTrue(cpu.getNegativeFlag());
+    }
+
+    @Test
+    public void test_ora_requiresCmosCpu() throws Exception {
+        makeNmosCpu();
+
+        // Set some initial values in zero page.
+        bus.write(0x30, 0x00);
+        bus.write(0x31, 0x10);
+
+        bus.write(0x40, 0x01);
+        bus.write(0x41, 0x10);
+
+        bus.write(0x50, 0x02);
+        bus.write(0x51, 0x10);
+
+        bus.write(0x60, 0x03);
+        bus.write(0x61, 0x10);
+
+        bus.write(0x1000, 0x11);
+        bus.write(0x1001, 0x22);
+        bus.write(0x1002, 0x44);
+        bus.write(0x1003, 0x88);
+
+        bus.loadProgram(0x12, 0x30,  // ORA ($30)
+                        0x12, 0x40,  // ORA ($40)
+                        0x12, 0x50,  // ORA ($50)
+                        0x12, 0x60); // ORA ($60)
+
+
+        assertEquals(0x00, cpu.getAccumulator());
+
+        boolean zState = cpu.getZeroFlag();
+        boolean nState = cpu.getNegativeFlag();
+
+        // 0x00 | 0x11 = 0x11, but not implemented in NMOS cpu
+        cpu.step();
+        assertEquals(0x00, cpu.getAccumulator());
+        assertEquals(zState, cpu.getZeroFlag());         // unchanged
+        assertEquals(nState, cpu.getNegativeFlag());     // unchanged
+
+        // 0x11 | 0x22 = 0x33, but not implemented in NMOS cpu
+        cpu.step();
+        assertEquals(0x00, cpu.getAccumulator());
+        assertEquals(zState, cpu.getZeroFlag());         // unchanged
+        assertEquals(nState, cpu.getNegativeFlag());     // unchanged
+
+        // 0x33 | 0x44 = 0x77, but not implemented in NMOS cpu
+        cpu.step();
+        assertEquals(0x00, cpu.getAccumulator());
+        assertEquals(zState, cpu.getZeroFlag());         // unchanged
+        assertEquals(nState, cpu.getNegativeFlag());     // unchanged
+
+        // 0x77 | 0x88 = 0xff, but not implemented in NMOS cpu
+        cpu.step();
+        assertEquals(0x00, cpu.getAccumulator());
+        assertEquals(zState, cpu.getZeroFlag());         // unchanged
+        assertEquals(nState, cpu.getNegativeFlag());     // unchanged
+    }
+
+    @Test
+    public void test_and() throws Exception {
+        makeCmosCpu();
+
+        // Set some initial values in zero page.
+        bus.write(0x30, 0x00);
+        bus.write(0x31, 0x10);
+
+        bus.write(0x40, 0x01);
+        bus.write(0x41, 0x10);
+
+        bus.write(0x50, 0x02);
+        bus.write(0x51, 0x10);
+
+        bus.write(0x1000, 0x33);
+        bus.write(0x1001, 0x11);
+        bus.write(0x1002, 0x88);
+
+        bus.loadProgram(0x32, 0x30,  // AND ($30)
+                        0x32, 0x40,  // AND ($40)
+                        0x32, 0x50); // AND ($50)
+
+        cpu.setAccumulator(0xff);
+
+        // 0xFF & 0x33 == 0x33
+        cpu.step();
+        assertEquals(0x33, cpu.getAccumulator());
+        assertFalse(cpu.getZeroFlag());
+        assertFalse(cpu.getNegativeFlag());
+
+        // 0x33 & 0x11 == 0x11
+        cpu.step();
+        assertEquals(0x11, cpu.getAccumulator());
+        assertFalse(cpu.getZeroFlag());
+        assertFalse(cpu.getNegativeFlag());
+
+        // 0x11 & 0x80 == 0
+        cpu.step();
+        assertEquals(0, cpu.getAccumulator());
+        assertTrue(cpu.getZeroFlag());
+        assertFalse(cpu.getNegativeFlag());
+    }
+
+    @Test
+    public void test_and_requiresCmosCpu() throws Exception {
+        makeNmosCpu();
+
+        // Set some initial values in zero page.
+        bus.write(0x30, 0x00);
+        bus.write(0x31, 0x10);
+
+        bus.write(0x40, 0x01);
+        bus.write(0x41, 0x10);
+
+        bus.write(0x50, 0x02);
+        bus.write(0x51, 0x10);
+
+        bus.write(0x1000, 0x33);
+        bus.write(0x1001, 0x11);
+        bus.write(0x1002, 0x88);
+
+        bus.loadProgram(0x32, 0x30,  // AND ($30)
+                        0x32, 0x40,  // AND ($40)
+                        0x32, 0x50); // AND ($50)
+
+
+        cpu.setAccumulator(0xff);
+
+        boolean zState = cpu.getZeroFlag();
+        boolean nState = cpu.getNegativeFlag();
+
+        // 0xFF & 0x33 == 0x33, but not implemented in NMOS cpu
+        cpu.step();
+        assertEquals(0xff, cpu.getAccumulator());
+        assertEquals(zState, cpu.getZeroFlag());
+        assertEquals(nState, cpu.getNegativeFlag());
+
+        // 0x33 & 0x11 == 0x11, but not implemented in NMOS cpu
+        cpu.step();
+        assertEquals(0xff, cpu.getAccumulator());
+        assertEquals(zState, cpu.getZeroFlag());
+        assertEquals(nState, cpu.getNegativeFlag());
+
+        // 0x11 & 0x80 == 0, but not implemented in NMOS cpu
+        cpu.step();
+        assertEquals(0xff, cpu.getAccumulator());
+        assertEquals(zState, cpu.getZeroFlag());
+        assertEquals(nState, cpu.getNegativeFlag());
+    }
+
+    @Test
+    public void test_eor() throws Exception {
+        makeCmosCpu();
+
+        // Set some initial values in zero page.
+        bus.write(0x30, 0x00);
+        bus.write(0x31, 0x10);
+
+        bus.write(0x40, 0x01);
+        bus.write(0x41, 0x10);
+
+        bus.write(0x50, 0x02);
+        bus.write(0x51, 0x10);
+
+        bus.write(0x60, 0x03);
+        bus.write(0x61, 0x10);
+
+        bus.write(0x1000, 0x00);
+        bus.write(0x1001, 0xff);
+        bus.write(0x1002, 0x33);
+        bus.write(0x1003, 0x44);
+
+        bus.loadProgram(0x52, 0x30,  // AND ($30)
+                        0x52, 0x40,  // AND ($40)
+                        0x52, 0x50,  // EOR ($50)
+                        0x52, 0x60); // AND ($60)
+
+
+        cpu.setAccumulator(0x88);
+
+        cpu.step();
+        assertEquals(0x88, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x77, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x44, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x00, cpu.getAccumulator());
+    }
+
+    @Test
+    public void test_eor_requiresCmosCpu() throws Exception {
+        makeNmosCpu();
+
+        // Set some initial values in zero page.
+        bus.write(0x30, 0x00);
+        bus.write(0x31, 0x10);
+
+        bus.write(0x40, 0x01);
+        bus.write(0x41, 0x10);
+
+        bus.write(0x50, 0x02);
+        bus.write(0x51, 0x10);
+
+        bus.write(0x60, 0x03);
+        bus.write(0x61, 0x10);
+
+        bus.write(0x1000, 0x00);
+        bus.write(0x1001, 0xff);
+        bus.write(0x1002, 0x33);
+        bus.write(0x1003, 0x44);
+
+        bus.loadProgram(0x52, 0x30,  // AND ($30)
+                        0x52, 0x40,  // AND ($40)
+                        0x52, 0x50,  // EOR ($50)
+                        0x52, 0x60); // AND ($60)
+
+
+        cpu.setAccumulator(0x88);
+
+        cpu.step();
+        assertEquals(0x88, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x88, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x88, cpu.getAccumulator());
+
+        cpu.step();
+        assertEquals(0x88, cpu.getAccumulator());
+    }
+}

src/test/java/com/loomcom/symon/HexUtilTest.java

@@ -1,42 +0,0 @@
-package com.loomcom.symon;
-
-import com.loomcom.symon.util.HexUtil;
-import junit.framework.TestCase;
-
-public class HexUtilTest extends TestCase {
-    public void testByteToHex() {
-        assertEquals("FE", HexUtil.byteToHex(0xfe));
-        assertEquals("00", HexUtil.byteToHex(0));
-        assertEquals("0A", HexUtil.byteToHex(10));
-    }
-
-    public void testByteToHexIgnoresSign() {
-        assertEquals("FF", HexUtil.byteToHex(-1));
-    }
-
-    public void testByteToHexMasksLowByte() {
-        assertEquals("FE", HexUtil.byteToHex(0xfffe));
-        assertEquals("00", HexUtil.byteToHex(0xff00));
-    }
-
-    public void testWordToHex() {
-        assertEquals("0000", HexUtil.wordToHex(0));
-        assertEquals("FFFF", HexUtil.wordToHex(65535));
-        assertEquals("FFFE", HexUtil.wordToHex(65534));
-    }
-
-    public void testWordToHexIgnoresSign() {
-        assertEquals("FFFF", HexUtil.wordToHex(-1));
-    }
-
-    public void testWordToHexMasksTwoLowBytes() {
-        assertEquals("FFFE", HexUtil.wordToHex(0xfffffe));
-        assertEquals("FF00", HexUtil.wordToHex(0xffff00));
-    }
-
-    public void testAllBytesAreCorrect() {
-        for (int i = 0; i <= 0xff; i++) {
-            assertEquals(String.format("%02X", i), HexUtil.byteToHex(i));
-        }
-    }
-}

src/test/java/com/loomcom/symon/UtilsTest.java

@@ -0,0 +1,42 @@
+package com.loomcom.symon;
+
+import com.loomcom.symon.util.Utils;
+import junit.framework.TestCase;
+
+public class UtilsTest extends TestCase {
+    public void testByteToHex() {
+        assertEquals("FE", Utils.byteToHex(0xfe));
+        assertEquals("00", Utils.byteToHex(0));
+        assertEquals("0A", Utils.byteToHex(10));
+    }
+
+    public void testByteToHexIgnoresSign() {
+        assertEquals("FF", Utils.byteToHex(-1));
+    }
+
+    public void testByteToHexMasksLowByte() {
+        assertEquals("FE", Utils.byteToHex(0xfffe));
+        assertEquals("00", Utils.byteToHex(0xff00));
+    }
+
+    public void testWordToHex() {
+        assertEquals("0000", Utils.wordToHex(0));
+        assertEquals("FFFF", Utils.wordToHex(65535));
+        assertEquals("FFFE", Utils.wordToHex(65534));
+    }
+
+    public void testWordToHexIgnoresSign() {
+        assertEquals("FFFF", Utils.wordToHex(-1));
+    }
+
+    public void testWordToHexMasksTwoLowBytes() {
+        assertEquals("FFFE", Utils.wordToHex(0xfffffe));
+        assertEquals("FF00", Utils.wordToHex(0xffff00));
+    }
+
+    public void testAllBytesAreCorrect() {
+        for (int i = 0; i <= 0xff; i++) {
+            assertEquals(String.format("%02X", i), Utils.byteToHex(i));
+        }
+    }
+}