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:** 1.2.0
+**Version:** 1.2.1
 
-**Last Updated:** 3 January, 2016
+**Last Updated:** 8 January, 2016
 
 See the file COPYING for license.
 
@@ -235,6 +235,9 @@ 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.
   

pom.xml

@@ -4,7 +4,7 @@
     <groupId>com.loomcom.symon</groupId>
     <artifactId>symon</artifactId>
     <packaging>jar</packaging>
-    <version>1.2.0</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>
+                    <source>1.7</source>
-                    <target>1.8</target>
+                    <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/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) {
+        for (int address = startAddress; address <= endAddress; ++address) {
-            if(deviceAddressArray[address - startAddress] == null) {
+            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

@@ -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) {
@@ -204,6 +204,13 @@ public class Cpu implements InstructionTable {
                     case 3: // Absolute
                         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) {
                             effectiveAddress = zpyAddress(state.args[0]);
@@ -258,13 +265,11 @@ public class Cpu implements InstructionTable {
 
             /** Single Byte Instructions; Implied and Relative **/
             case 0x00: // BRK - Force Interrupt - Implied
-                if (!getIrqDisableFlag()) {
+                handleBrk(state.pc + 1);
-                    handleIrq(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()) {
@@ -400,11 +405,12 @@ public class Cpu implements InstructionTable {
             case 0x4c: // JMP - Absolute
                 state.pc = Utils.address(state.args[0], state.args[1]);
                 break;
+            // TODO: 65C02 instruction 0x7C, JMP (Indirect,X)
             case 0x6c: // JMP - Indirect
                 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 = Utils.address(0x00, state.args[1]);
                 } else {
@@ -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 {
+    private void handleInterrupt(int returnPc, int vectorLow, int vectorHigh, boolean isBreak) throws MemoryAccessException {
-        // Set the break flag before pushing.
+
-        setBreakFlag();
+        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
@@ -1321,6 +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.
      */
@@ -1329,21 +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;
         }
 

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,
+        NMOS_6502,
-
-        /**
-         * 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,
 
         /**
          * 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,
+        "BRK", "ORA",  null,  null,  null, "ORA", "ASL",  null,  // 0x00-0x07
-        "PHP", "ORA", "ASL",  null,  null, "ORA", "ASL",  null,
+        "PHP", "ORA", "ASL",  null,  null, "ORA", "ASL",  null,  // 0x08-0x0f
-        "BPL", "ORA",  null,  null,  null, "ORA", "ASL",  null,
+        "BPL", "ORA", "ORA",  null,  null, "ORA", "ASL",  null,  // 0x10-0x17
-        "CLC", "ORA",  null,  null,  null, "ORA", "ASL",  null,
+        "CLC", "ORA",  null,  null,  null, "ORA", "ASL",  null,  // 0x18-0x1f
-        "JSR", "AND",  null,  null, "BIT", "AND", "ROL",  null,
+        "JSR", "AND",  null,  null, "BIT", "AND", "ROL",  null,  // 0x20-0x27
-        "PLP", "AND", "ROL",  null, "BIT", "AND", "ROL",  null,
+        "PLP", "AND", "ROL",  null, "BIT", "AND", "ROL",  null,  // 0x28-0x2f
-        "BMI", "AND",  null,  null,  null, "AND", "ROL",  null,
+        "BMI", "AND", "AND",  null,  null, "AND", "ROL",  null,  // 0x30-0x37
-        "SEC", "AND",  null,  null,  null, "AND", "ROL",  null,
+        "SEC", "AND",  null,  null,  null, "AND", "ROL",  null,  // 0x38-0x3f
-        "RTI", "EOR",  null,  null,  null, "EOR", "LSR",  null,
+        "RTI", "EOR",  null,  null,  null, "EOR", "LSR",  null,  // 0x40-0x47
-        "PHA", "EOR", "LSR",  null, "JMP", "EOR", "LSR",  null,
+        "PHA", "EOR", "LSR",  null, "JMP", "EOR", "LSR",  null,  // 0x48-0x4f
-        "BVC", "EOR",  null,  null,  null, "EOR", "LSR",  null,
+        "BVC", "EOR", "EOR",  null,  null, "EOR", "LSR",  null,  // 0x50-0x57
-        "CLI", "EOR",  null,  null,  null, "EOR", "LSR",  null,
+        "CLI", "EOR",  null,  null,  null, "EOR", "LSR",  null,  // 0x58-0x5f
-        "RTS", "ADC",  null,  null,  null, "ADC", "ROR",  null,
+        "RTS", "ADC",  null,  null,  null, "ADC", "ROR",  null,  // 0x60-0x67
-        "PLA", "ADC", "ROR",  null, "JMP", "ADC", "ROR",  null,
+        "PLA", "ADC", "ROR",  null, "JMP", "ADC", "ROR",  null,  // 0x68-0x6f
-        "BVS", "ADC",  null,  null,  null, "ADC", "ROR",  null,
+        "BVS", "ADC", "ADC",  null,  null, "ADC", "ROR",  null,  // 0x70-0x77
-        "SEI", "ADC",  null,  null,  null, "ADC", "ROR",  null,
+        "SEI", "ADC",  null,  null, "JMP", "ADC", "ROR",  null,  // 0x78-0x7f
-        "BCS", "STA",  null,  null, "STY", "STA", "STX",  null,
+        "BCS", "STA",  null,  null, "STY", "STA", "STX",  null,  // 0x80-0x87
-        "DEY",  null, "TXA",  null, "STY", "STA", "STX",  null,
+        "DEY",  null, "TXA",  null, "STY", "STA", "STX",  null,  // 0x88-0x8f
-        "BCC", "STA",  null,  null, "STY", "STA", "STX",  null,
+        "BCC", "STA", "STA",  null, "STY", "STA", "STX",  null,  // 0x90-0x97
-        "TYA", "STA", "TXS",  null,  null, "STA",  null,  null,
+        "TYA", "STA", "TXS",  null,  null, "STA",  null,  null,  // 0x98-0x9f
-        "LDY", "LDA", "LDX",  null, "LDY", "LDA", "LDX",  null,
+        "LDY", "LDA", "LDX",  null, "LDY", "LDA", "LDX",  null,  // 0xa0-0xa7
-        "TAY", "LDA", "TAX",  null, "LDY", "LDA", "LDX",  null,
+        "TAY", "LDA", "TAX",  null, "LDY", "LDA", "LDX",  null,  // 0xa8-0xaf
-        "BCS", "LDA",  null,  null, "LDY", "LDA", "LDX",  null,
+        "BCS", "LDA", "LDA",  null, "LDY", "LDA", "LDX",  null,  // 0xb0-0xb7
-        "CLV", "LDA", "TSX",  null, "LDY", "LDA", "LDX",  null,
+        "CLV", "LDA", "TSX",  null, "LDY", "LDA", "LDX",  null,  // 0xb8-0xbf
-        "CPY", "CMP",  null,  null, "CPY", "CMP", "DEC",  null,
+        "CPY", "CMP",  null,  null, "CPY", "CMP", "DEC",  null,  // 0xc0-0xc7
-        "INY", "CMP", "DEX",  null, "CPY", "CMP", "DEC",  null,
+        "INY", "CMP", "DEX",  null, "CPY", "CMP", "DEC",  null,  // 0xc8-0xcf
-        "BNE", "CMP",  null,  null,  null, "CMP", "DEC",  null,
+        "BNE", "CMP", "CMP",  null,  null, "CMP", "DEC",  null,  // 0xd0-0xd7
-        "CLD", "CMP",  null,  null,  null, "CMP", "DEC",  null,
+        "CLD", "CMP",  null,  null,  null, "CMP", "DEC",  null,  // 0xd8-0xdf
-        "CPX", "SBC",  null,  null, "CPX", "SBC", "INC",  null,
+        "CPX", "SBC",  null,  null, "CPX", "SBC", "INC",  null,  // 0xe0-0xe7
-        "INX", "SBC", "NOP",  null, "CPX", "SBC", "INC",  null,
+        "INX", "SBC", "NOP",  null, "CPX", "SBC", "INC",  null,  // 0xe8-0xef
-        "BEQ", "SBC",  null,  null,  null, "SBC", "INC",  null,
+        "BEQ", "SBC", "SBC",  null,  null, "SBC", "INC",  null,  // 0xf0-0xf7
-        "SED", "SBC",  null,  null,  null, "SBC", "INC",  null
+        "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,
+        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 0, 3, 3, 0,   // 0x00-0x0f
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
+        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,
+        3, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0x20-0x2f
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
+        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,
+        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0x40-0x4f
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
+        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,
+        1, 2, 0, 0, 0, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0x60-0x6f
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
+        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,
+        2, 2, 0, 0, 2, 2, 2, 0, 1, 0, 1, 0, 3, 3, 3, 0,   // 0x80-0x8f
-        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, 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,
+        2, 2, 2, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0xa0-0xaf
-        2, 2, 0, 0, 2, 2, 2, 0, 1, 3, 1, 0, 3, 3, 3, 0,
+        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,
+        2, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0xc0-0xcf
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0,
+        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,
+        2, 2, 0, 0, 2, 2, 2, 0, 1, 2, 1, 0, 3, 3, 3, 0,   // 0xe0-0xef
-        2, 2, 0, 0, 0, 2, 2, 0, 1, 3, 0, 0, 0, 3, 3, 0
+        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 = {
+    int[] instructionClocksNmos = {
-        7, 6, 0, 0, 0, 3, 5, 0, 3, 2, 2, 0, 0, 4, 6, 0,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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,
+        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
+        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(() -> {
+            SwingUtilities.invokeLater(new Runnable() {
-                try {
+                @Override
-                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
+                public void run() {
-                    // Create the main UI window
+                    try {
-                    simulator.createAndShowUi();
+                        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-                } catch (Exception e) {
+                        // Create the main UI window
-                    e.printStackTrace();
+                        simulator.createAndShowUi();
+                    } catch (Exception e) {
+                        e.printStackTrace();
+                    }
                 }
             });
         

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

@@ -185,13 +185,16 @@ public class Simulator {
         JButton hardResetButton = new JButton("Hard Reset");
 
         stepCountBox = new JComboBox<>(STEPS);
-        stepCountBox.addActionListener(actionEvent -> {
+        stepCountBox.addActionListener(new ActionListener() {
-            try {
+            @Override
-                JComboBox cb = (JComboBox) actionEvent.getSource();
+            public void actionPerformed(ActionEvent actionEvent) {
-                stepsPerClick = Integer.parseInt((String) cb.getSelectedItem());
+                try {
-            } catch (NumberFormatException ex) {
+                    JComboBox cb = (JComboBox) actionEvent.getSource();
-                stepsPerClick = 1;
+                    stepsPerClick = Integer.parseInt((String) cb.getSelectedItem());
-                stepCountBox.setSelectedIndex(0);
+                } 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 -> {
+        runStopButton.addActionListener(new ActionListener() {
-            if (runLoop != null && runLoop.isRunning()) {
+            @Override
-                handleStop();
+            public void actionPerformed(ActionEvent actionEvent) {
-            } else {
+                if (runLoop != null && runLoop.isRunning()) {
-                handleStart();
+                    Simulator.this.handleStop();
+                } else {
+                    Simulator.this.handleStart();
+                }
             }
         });
 
-        stepButton.addActionListener(actionEvent -> handleStep(stepsPerClick));
+        stepButton.addActionListener(new ActionListener() {
-
+            @Override
-        softResetButton.addActionListener(actionEvent -> {
+            public void actionPerformed(ActionEvent actionEvent) {
-            // If this was a CTRL-click, do a hard reset.
+                Simulator.this.handleStep(stepsPerClick);
-            handleReset(false);
+            }
         });
 
-        hardResetButton.addActionListener(actionEvent -> {
+        softResetButton.addActionListener(new ActionListener() {
-            // If this was a CTRL-click, do a hard reset.
+            @Override
-            handleReset(true);
+            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(() -> {
+            SwingUtilities.invokeLater(new Runnable() {
-                // Don't allow step while the simulator is running
+                @Override
-                stepButton.setEnabled(false);
+                public void run() {
-                stepCountBox.setEnabled(false);
+                    // Don't allow step while the simulator is running
-                menuBar.simulatorDidStart();
+                    stepButton.setEnabled(false);
-                // Toggle the state of the run button
+                    stepCountBox.setEnabled(false);
-                runStopButton.setText("Stop");
+                    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(() -> {
+            SwingUtilities.invokeLater(new Runnable() {
-                statusPane.updateState();
+                @Override
-                memoryWindow.updateState();
+                public void run() {
-                runStopButton.setText("Run");
+                    statusPane.updateState();
-                stepButton.setEnabled(true);
+                    memoryWindow.updateState();
-                stepCountBox.setEnabled(true);
+                    runStopButton.setText("Run");
-                if (traceLog.isVisible()) {
+                    stepButton.setEnabled(true);
-                    traceLog.refresh();
+                    stepCountBox.setEnabled(true);
+                    if (traceLog.isVisible()) {
+                        traceLog.refresh();
+                    }
+                    menuBar.simulatorDidStop();
+                    traceLog.simulatorDidStop();
                 }
-                menuBar.simulatorDidStop();
-                traceLog.simulatorDidStop();
             });
 
             isRunning = false;
@@ -480,9 +503,12 @@ public class Simulator {
                             // Now load the program at the starting address.
                             loadProgram(program, preferences.getProgramStartAddress());
 
-                            SwingUtilities.invokeLater(() -> {
+                            SwingUtilities.invokeLater(new Runnable() {
-                                console.reset();
+                                @Override
-                                breakpoints.refresh();
+                                public void run() {
+                                    console.reset();
+                                    breakpoints.refresh();
+                                }
                             });
 
                             // TODO: "Don't Show Again" checkbox
@@ -623,9 +649,12 @@ public class Simulator {
         }
 
         public void actionPerformed(ActionEvent actionEvent) {
-            SwingUtilities.invokeLater(() -> {
+            SwingUtilities.invokeLater(new Runnable() {
-                console.setFont(new Font("Monospaced", Font.PLAIN, size));
+                @Override
-                mainWindow.pack();
+                public void run() {
+                    console.setFont(new Font("Monospaced", Font.PLAIN, size));
+                    mainWindow.pack();
+                }
             });
         }
     }
@@ -889,12 +918,15 @@ public class Simulator {
 
     private void updateVisibleState() {
         // Immediately update the UI.
-        SwingUtilities.invokeLater(() -> {
+        SwingUtilities.invokeLater(new Runnable() {
-            // Now update the state
+            @Override
-            statusPane.updateState();
+            public void run() {
-            memoryWindow.updateState();
+                // Now update the state
-            if (traceLog.shouldUpdate()) {
+                statusPane.updateState();
-                traceLog.refresh();
+                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

@@ -30,7 +30,10 @@ 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;
 
 /**
@@ -62,21 +65,24 @@ public class BreakpointsWindow extends JFrame {
         breakpointsPanel.setLayout(new BorderLayout());
         breakpointsPanel.setBorder(new EmptyBorder(10, 10, 10, 10));
 
-        JButton addButton = new JButton("Add");
+        final JButton addButton = new JButton("Add");
-        JButton removeButton = new JButton("Del");
+        final JButton removeButton = new JButton("Del");
         removeButton.setEnabled(false);
 
-        JTextField addTextField = new JTextField(4);
+        final JTextField addTextField = new JTextField(4);
 
-        JTable breakpointsTable = new JTable(breakpoints);
+        final JTable breakpointsTable = new JTable(breakpoints);
         breakpointsTable.setShowGrid(true);
         breakpointsTable.setGridColor(Color.LIGHT_GRAY);
         breakpointsTable.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
-        breakpointsTable.getSelectionModel().addListSelectionListener(e -> {
+        breakpointsTable.getSelectionModel().addListSelectionListener(new ListSelectionListener() {
-            if (e.getFirstIndex() > -1) {
+            @Override
-                removeButton.setEnabled(true);
+            public void valueChanged(ListSelectionEvent e) {
-            } else {
+                if (e.getFirstIndex() > -1) {
-                removeButton.setEnabled(false);
+                    removeButton.setEnabled(true);
+                } else {
+                    removeButton.setEnabled(false);
+                }
             }
         });
 
@@ -86,37 +92,45 @@ public class BreakpointsWindow extends JFrame {
 
         breakpointsPanel.add(scrollPane, BorderLayout.CENTER);
 
-        ActionListener addBreakpointListener = e -> {
+        ActionListener addBreakpointListener = new ActionListener() {
-            int value = -1;
+            @Override
+            public void actionPerformed(ActionEvent e) {
+                int value;
 
-            String newBreakpoint = addTextField.getText();
+                String newBreakpoint = addTextField.getText();
 
-            if (newBreakpoint == null || newBreakpoint.isEmpty()) {
+                if (newBreakpoint == null || newBreakpoint.isEmpty()) {
-                return;
+                    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);
             }
-
-            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);
         };
 
         addButton.addActionListener(addBreakpointListener);
         addTextField.addActionListener(addBreakpointListener);
 
-        removeButton.addActionListener(e -> breakpoints.removeBreakpointAtIndex(breakpointsTable.getSelectedRow()));
+        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/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 -> {
+        cancelButton.addActionListener(new ActionListener() {
-            updateUi();
+            @Override
-            dialog.setVisible(false);
+            public void actionPerformed(ActionEvent actionEvent) {
+                PreferencesDialog.this.updateUi();
+                dialog.setVisible(false);
+            }
         });
 
-        applyButton.addActionListener(actionEvent -> {
+        applyButton.addActionListener(new ActionListener() {
-            haltOnBreak = haltOnBreakCheckBox.isSelected();
+            @Override
-            programLoadAddress = hexToInt(programLoadAddressField.getText());
+            public void actionPerformed(ActionEvent actionEvent) {
-            updateUi();
+                haltOnBreak = haltOnBreakCheckBox.isSelected();
-            // TODO: Actually check to see if values have changed, don't assume.
+                programLoadAddress = PreferencesDialog.this.hexToInt(programLoadAddressField.getText());
-            setChanged();
+                PreferencesDialog.this.updateUi();
-            PreferencesDialog.this.notifyObservers();
+                // TODO: Actually check to see if values have changed, don't assume.
-            dialog.setVisible(false);
+                PreferencesDialog.this.setChanged();
+                PreferencesDialog.this.notifyObservers();
+                dialog.setVisible(false);
+            }
         });
 
         buttonsContainer.add(applyButton);

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

@@ -31,6 +31,8 @@ import javax.swing.*;
 import javax.swing.border.Border;
 import javax.swing.border.EtchedBorder;
 import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
 
 /**
  * UI component that displays the current state of the simulated CPU.
@@ -162,59 +164,74 @@ public class StatusPanel extends JPanel {
         yField = makeTextField(SMALL_TEXT_FIELD_SIZE, true);
 
         // Make fields editable
-        pcField.addActionListener(e -> {
+        pcField.addActionListener(new ActionListener() {
-            try {
+            @Override
-                int newVal = getHexVal(pcField) & 0xffff;
+            public void actionPerformed(ActionEvent e) {
-                machine.getCpu().setProgramCounter(newVal);
+                try {
-            } catch (Exception ex) {
+                    int newVal = StatusPanel.this.getHexVal(pcField) & 0xffff;
-                // Swallow exception
+                    machine.getCpu().setProgramCounter(newVal);
-            }
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        spField.addActionListener(e -> {
+        spField.addActionListener(new ActionListener() {
-            try {
+            @Override
-                int newVal = getHexVal(spField) & 0xff;
+            public void actionPerformed(ActionEvent e) {
-                machine.getCpu().setStackPointer(newVal);
+                try {
-            } catch (Exception ex) {
+                    int newVal = StatusPanel.this.getHexVal(spField) & 0xff;
-                // Swallow exception
+                    machine.getCpu().setStackPointer(newVal);
-            }
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        aField.addActionListener(e -> {
+        aField.addActionListener(new ActionListener() {
-            try {
+            @Override
-                int newVal = getHexVal(aField) & 0xff;
+            public void actionPerformed(ActionEvent e) {
-                machine.getCpu().setAccumulator(newVal);
+                try {
-            } catch (Exception ex) {
+                    int newVal = StatusPanel.this.getHexVal(aField) & 0xff;
-                // Swallow exception
+                    machine.getCpu().setAccumulator(newVal);
-            }
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        xField.addActionListener(e -> {
+        xField.addActionListener(new ActionListener() {
-            try {
+            @Override
-                int newVal = getHexVal(xField) & 0xff;
+            public void actionPerformed(ActionEvent e) {
-                machine.getCpu().setXRegister(newVal);
+                try {
-            } catch (Exception ex) {
+                    int newVal = StatusPanel.this.getHexVal(xField) & 0xff;
-                // Swallow exception
+                    machine.getCpu().setXRegister(newVal);
-            }
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
-        yField.addActionListener(e -> {
+        yField.addActionListener(new ActionListener() {
-            try {
+            @Override
-                int newVal = getHexVal(yField) & 0xff;
+            public void actionPerformed(ActionEvent e) {
-                machine.getCpu().setYRegister(newVal);
+                try {
-            } catch (Exception ex) {
+                    int newVal = StatusPanel.this.getHexVal(yField) & 0xff;
-                // Swallow exception
+                    machine.getCpu().setYRegister(newVal);
-            }
+                } catch (Exception ex) {
+                    // Swallow exception
+                }
 
-            updateState();
+                StatusPanel.this.updateState();
+            }
         });
 
         constraints.anchor = GridBagConstraints.LINE_START;

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(() -> {
+            SwingUtilities.invokeLater(new Runnable() {
-                if (cursorBlinkRate > 0) {
+                @Override
-                    hideCursor = !hideCursor;
+                public void run() {
-                    repaint();
+                    if (cursorBlinkRate > 0) {
+                        hideCursor = !hideCursor;
+                        VideoWindow.this.repaint();
+                    }
                 }
             });
         }

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
+        // Triggers the BRK
-        // of the Interrupt Disable flag
         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
+        // Interrupt vector held 0x1234, so we should be there.
-        assertEquals(0x0206, cpu.getProgramCounter());
+        assertEquals(0x1234, cpu.getProgramCounter());
-        // Empty stack
+        assertEquals(0xfc, cpu.getStackPointer());
-        assertEquals(0xff, 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

@@ -241,6 +241,7 @@ public class CpuTest extends TestCase {
 
     public void testSetProcessorStatus() {
         // Default
+
         assertFalse(cpu.getZeroFlag());
         assertFalse(cpu.getZeroFlag());
         assertFalse(cpu.getIrqDisableFlag());
@@ -384,6 +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();
@@ -498,6 +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();

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());
+    }
+}