Bug Fixes and Copyright Date Change

The simulator now passes Klaus Dormann's 6502 Functional Test suite for
the first time.

Bug Fixes:

- PHP was not correctly setting the Break bit on the stack copy of the
  processor status, so subsequent PLA's would not set the Break status
  flag.

- The CPU had swapped NMI and IRQ reset vectors, so RTI was failing.

- BRK was pushing PC + 2 onto the stack, instead of PC + 1

- (Zero Page,X) addressing mode did not correctly wrap on zero page
  boundaries.

- The instruction table used for disassembly had addressing modes
  of LDA $B9 and $BD reversed. This did not affect behavior, only
  disassembly of these instructions.

Other:

- Updated copyright date for 2013.

- Started migrating old JUnit 3 style tests to JUnit 4 annotations.

README.md

@@ -4,11 +4,11 @@ SYMON - A 6502 System Simulator
 **NOTE: THIS IS BETA QUALITY SOFTWARE UNDER ACTIVE DEVELOPMENT.  Feedback is
 welcome!**
 
-**Version:** 0.8.1
+**Version:** 0.8.2
 
-**Last Updated:** 30 December, 2012
+**Last Updated:** 01 January, 2013
 
-Copyright (c) 2008-2012 Seth J. Morabito <web@loomcom.com>
+Copyright (c) 2008-2013 Seth J. Morabito <web@loomcom.com>
 
 See the file COPYING for license.
 
@@ -25,6 +25,11 @@ documentation, and extensive test suites for validating correctness.
 Symon simulates a complete system with a 1 MHz NMOS 6502, 32KB of RAM,
 16KB of ROM, a 6551 ACIA, and a 6522 VIA.
 
+Symon has extensive unit tests to verify correctness, and fully passes
+Klaus Dormann's 6502 Functional Test Suite as of version 0.8.2
+(See [this thread on the 6502.org Forums] (http://forum.6502.org/viewtopic.php?f=2&t=2241)
+for more information about this functional test suite).
+
 ## 2.0 Requirements
 
   - Java 1.5 or higher
@@ -135,14 +140,15 @@ running.
 
 ## 5.0 Revision History
 
-  - 0.8.1: 30 December, 2012
+  - **0.8.2:** 01 January, 2013 - Fully passes Klaus Dormann's 6502 Functional Test suite!
-  - 0.8.0: 29 December, 2012
+  - **0.8.1:** 30 December, 2012
-  - 0.7.0: 9 December, 2012
+  - **0.8.0:** 29 December, 2012
-  - 0.6: 5 November, 2012
+  - **0.7.0:** 9 December, 2012
-  - 0.5: 21 October, 2012
+  - **0.6:** 5 November, 2012
-  - 0.3: 14 October, 2012
+  - **0.5:** 21 October, 2012 - Able to run Enhanced BASIC for the first time.
-  - 0.2: 22 April, 2012
+  - **0.3:** 14 October, 2012
-  - 0.1: 20 January, 2010
+  - **0.2:** 22 April, 2012
+  - **0.1:** 20 January, 2010
 
 ## 6.0 To Do
 

pom.xml

@@ -4,7 +4,7 @@
     <groupId>com.loomcom.symon</groupId>
     <artifactId>symon</artifactId>
     <packaging>jar</packaging>
-    <version>0.8.1</version>
+    <version>0.8.2</version>
     <name>symon</name>
     <url>http://www.loomcom.com/symon</url>
     <properties>

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -44,14 +44,14 @@ public class Cpu implements InstructionTable {
     public static final int P_NEGATIVE    = 0x80;
 
     // NMI vector
-    public static final int IRQ_VECTOR_L = 0xfffa;
+    public static final int NMI_VECTOR_L = 0xfffa;
-    public static final int IRQ_VECTOR_H = 0xfffb;
+    public static final int NMI_VECTOR_H = 0xfffb;
     // Reset vector
     public static final int RST_VECTOR_L = 0xfffc;
     public static final int RST_VECTOR_H = 0xfffd;
     // IRQ vector
-    public static final int NMI_VECTOR_L = 0xfffe;
+    public static final int IRQ_VECTOR_L = 0xfffe;
-    public static final int NMI_VECTOR_H = 0xffff;
+    public static final int IRQ_VECTOR_H = 0xffff;
 
     // The delay in microseconds between steps.
     // TODO: Make configurable
@@ -214,7 +214,7 @@ public class Cpu implements InstructionTable {
             case 1:
                 switch (irAddressMode) {
                     case 0: // (Zero Page,X)
-                        tmp = state.args[0] + state.x;
+                        tmp = (state.args[0] + state.x) & 0xff;
                         effectiveAddress = address(bus.read(tmp), bus.read(tmp + 1));
                         break;
                     case 1: // Zero Page
@@ -252,9 +252,9 @@ public class Cpu implements InstructionTable {
                 if (!getIrqDisableFlag()) {
                     // Set the break flag before pushing.
                     setBreakFlag();
-                    // Push program counter + 2 onto the stack
+                    // Push program counter + 1 onto the stack
-                    stackPush((state.pc + 2 >> 8) & 0xff); // PC high byte
+                    stackPush((state.pc + 1 >> 8) & 0xff); // PC high byte
-                    stackPush(state.pc + 2 & 0xff);        // PC low byte
+                    stackPush(state.pc + 1 & 0xff);        // PC low byte
                     stackPush(state.getStatusFlag());
                     // Set the Interrupt Disabled flag.  RTI will clear it.
                     setIrqDisableFlag();
@@ -263,7 +263,8 @@ public class Cpu implements InstructionTable {
                 }
                 break;
             case 0x08: // PHP - Push Processor Status - Implied
-                stackPush(state.getStatusFlag());
+                // Break flag is always set in the stack value.
+                stackPush(state.getStatusFlag() | 0x10); 
                 break;
             case 0x10: // BPL - Branch if Positive - Relative
                 if (!getNegativeFlag()) {
@@ -1094,6 +1095,11 @@ public class Cpu implements InstructionTable {
     public void setStackPointer(int offset) {
         state.sp = offset;
     }
+
+    public int getInstruction() {
+        return state.ir;
+    }
+
     /**
      * @value The value of the Process Status Register bits to be set.
      */

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

@@ -241,8 +241,8 @@ public interface InstructionTable {
         Mode.ABS, Mode.ABS, Mode.ABS, Mode.NUL,   // 0xac-0xaf
         Mode.REL, Mode.INY, Mode.NUL, Mode.NUL,   // 0xb0-0xb3
         Mode.ZPX, Mode.ZPX, Mode.ZPY, Mode.NUL,   // 0xb4-0xb7
-        Mode.IMP, Mode.ABX, Mode.IMP, Mode.NUL,   // 0xb8-0xbb
+        Mode.IMP, Mode.ABY, Mode.IMP, Mode.NUL,   // 0xb8-0xbb
-        Mode.ABX, Mode.ABY, Mode.ABY, Mode.NUL,   // 0xbc-0xbf
+        Mode.ABX, Mode.ABX, Mode.ABY, Mode.NUL,   // 0xbc-0xbf
         Mode.IMM, Mode.XIN, Mode.NUL, Mode.NUL,   // 0xc0-0xc3
         Mode.ZPG, Mode.ZPG, Mode.ZPG, Mode.NUL,   // 0xc4-0xc7
         Mode.IMP, Mode.IMM, Mode.IMP, Mode.NUL,   // 0xc8-0xcb

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -451,9 +451,9 @@ public class Simulator implements Observer {
             });
 
             try {
-                while (isRunning && !(preferences.getHaltOnBreak() && cpu.getBreakFlag())) {
+                do {
                     step();
-                }
+                } while (shouldContinue());
             } catch (SymonException ex) {
                 logger.log(Level.SEVERE, "Exception in main simulator run thread. Exiting run.");
                 ex.printStackTrace();
@@ -475,6 +475,15 @@ public class Simulator implements Observer {
 
             isRunning = false;
         }
+
+        /**
+         * Returns true if the run loop should proceed to the next step.
+         *
+         * @return True if the run loop should proceed to the next step.
+         */
+        private boolean shouldContinue() {
+            return isRunning && !(preferences.getHaltOnBreak() && cpu.getInstruction() == 0x00);
+        }
     }
 
     class LoadProgramAction extends AbstractAction {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

src/main/java/com/loomcom/symon/exceptions/FifoUnderrunException.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

src/main/java/com/loomcom/symon/exceptions/MemoryAccessException.java

@@ -1,3 +1,26 @@
+/*
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
 package com.loomcom.symon.exceptions;
 
 /**

src/main/java/com/loomcom/symon/exceptions/MemoryRangeException.java

@@ -1,3 +1,26 @@
+/*
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
 package com.loomcom.symon.exceptions;
 
 /**

src/main/java/com/loomcom/symon/exceptions/SymonException.java

@@ -1,3 +1,26 @@
+/*
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
 package com.loomcom.symon.exceptions;
 
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2012 Seth J. Morabito <sethm@loomcom.com>
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the

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

@@ -1,3 +1,26 @@
+/*
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
 package com.loomcom.symon.util;
 
 import com.loomcom.symon.exceptions.*;

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

@@ -1,3 +1,26 @@
+/*
+ * Copyright (c) 2008-2013 Seth J. Morabito <sethm@loomcom.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
 package com.loomcom.symon.util;
 
 /**

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

@@ -3,14 +3,17 @@ package com.loomcom.symon;
 import com.loomcom.symon.devices.Memory;
 import com.loomcom.symon.exceptions.MemoryAccessException;
 import com.loomcom.symon.exceptions.MemoryRangeException;
-import junit.framework.*;
+import org.junit.*;
 
-public class CpuImpliedModeTest extends TestCase {
+import static org.junit.Assert.*;
 
-    protected Cpu    cpu;
+public class CpuImpliedModeTest {
-    protected Bus    bus;
+
+    protected Cpu cpu;
+    protected Bus bus;
     protected Memory mem;
 
+    @Before
     public void setUp() throws MemoryRangeException, MemoryAccessException {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
@@ -33,42 +36,43 @@ public class CpuImpliedModeTest extends TestCase {
         assertEquals(0x20, cpu.getProcessorStatus());
     }
 
-  /*
+    /*
-   * The following opcodes are tested for correctness in this file:
+     * The following opcodes are tested for correctness in this file:
-   *
+     *
-   * BRK - $00
+     * BRK - $00
-   * CLC - $18
+     * CLC - $18
-   * CLD - $d8
+     * CLD - $d8
-   * CLI - $58
+     * CLI - $58
-   * CLV - $B8
+     * CLV - $B8
-   *
+     *
-   * DEX - $ca
+     * DEX - $ca
-   * DEY - $88
+     * DEY - $88
-   * INX - $e8
+     * INX - $e8
-   * INY - $c8
+     * INY - $c8
-   * NOP - $ea
+     * NOP - $ea
-   *
+     *
-   * PHA - $48
+     * PHA - $48
-   * PHP - $08
+     * PHP - $08
-   * PLA - $68
+     * PLA - $68
-   * PLP - $28
+     * PLP - $28
-   * RTI - $40
+     * RTI - $40
-   *
+     *
-   * RTS - $60
+     * RTS - $60
-   * SEC - $38
+     * SEC - $38
-   * SED - $f8
+     * SED - $f8
-   * SEI - $78
+     * SEI - $78
-   * TAX - $aa
+     * TAX - $aa
-   *
+     *
-   * TAY - $a8
+     * TAY - $a8
-   * TSX - $ba
+     * TSX - $ba
-   * TXA - $8a
+     * TXA - $8a
-   * TXS - $9a
+     * TXS - $9a
-   * TYA - $98
+     * TYA - $98
-   */
+     */
 
-  /* BRK Tests - 0x00 */
+    /* BRK Tests - 0x00 */
 
+    @Test
     public void test_BRK() throws MemoryAccessException {
         cpu.setCarryFlag();
         cpu.setOverflowFlag();
@@ -80,15 +84,15 @@ public class CpuImpliedModeTest extends TestCase {
         assertEquals(0xff, cpu.getStackPointer());
 
         // Set the IRQ vector
-        bus.write(Cpu.IRQ_VECTOR_H, 0x12);
+        bus.write(0xffff, 0x12);
-        bus.write(Cpu.IRQ_VECTOR_L, 0x34);
+        bus.write(0xfffe, 0x34);
 
-        bus.loadProgram(0xea,
+        bus.loadProgram(0xea,  // NOP
-                        0xea,
+                        0xea,  // NOP
-                        0xea,
+                        0xea,  // NOP
-                        0x00,
+                        0x00,  // BRK
-                        0xea,
+                        0xea,  // NOP
-                        0xea);
+                        0xea); // NOP
 
         cpu.step(3); // Three NOP instructions
 
@@ -96,9 +100,9 @@ public class CpuImpliedModeTest extends TestCase {
 
         cpu.step(); // Triggers the BRK
 
-        // Was at PC = 0x204.  PC+2 should now be on the stack
+        // Was at PC = 0x204.  PC+1 should now be on the stack
         assertEquals(0x02, bus.read(0x1ff)); // PC high byte
-        assertEquals(0x06, bus.read(0x1fe)); // PC low byte
+        assertEquals(0x05, bus.read(0x1fe)); // PC low byte
         assertEquals(0x20 | Cpu.P_CARRY | Cpu.P_OVERFLOW | Cpu.P_BREAK,
                      bus.read(0x1fd));       // Processor Status, with B set
 
@@ -108,10 +112,11 @@ public class CpuImpliedModeTest extends TestCase {
 
         // 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.P_IRQ_DISABLE,
                      cpu.getProcessorStatus());
     }
 
+    @Test
     public void test_BRK_HonorsIrqDisableFlag() throws MemoryAccessException {
         cpu.setIrqDisableFlag();
 
@@ -144,6 +149,7 @@ public class CpuImpliedModeTest extends TestCase {
     }
 
     /* CLC - Clear Carry Flag - $18 */
+    @Test
     public void test_CLC() throws MemoryAccessException {
         cpu.setCarryFlag();
         assertTrue(cpu.getCarryFlag());
@@ -155,6 +161,7 @@ public class CpuImpliedModeTest extends TestCase {
     }
 
     /* CLD - Clear Decimal Mode Flag - $d8 */
+    @Test
     public void test_CLD() throws MemoryAccessException {
         cpu.setDecimalModeFlag();
         assertTrue(cpu.getDecimalModeFlag());
@@ -166,6 +173,7 @@ public class CpuImpliedModeTest extends TestCase {
     }
 
     /* CLI - Clear Interrupt Disabled Flag - $58 */
+    @Test
     public void test_CLI() throws MemoryAccessException {
         cpu.setIrqDisableFlag();
         assertTrue(cpu.getIrqDisableFlag());
@@ -177,6 +185,7 @@ public class CpuImpliedModeTest extends TestCase {
     }
 
     /* CLV - Clear Overflow Flag - $b8 */
+    @Test
     public void test_CLV() throws MemoryAccessException {
         cpu.setOverflowFlag();
         assertTrue(cpu.getOverflowFlag());
@@ -187,8 +196,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getOverflowFlag());
     }
 
-  /* DEX - Decrement the X register - $ca */
+    /* DEX - Decrement the X register - $ca */
-
+    @Test
     public void test_DEX() throws MemoryAccessException {
         bus.loadProgram(0xca);
         cpu.setXRegister(0x02);
@@ -198,6 +207,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_DEX_SetsZeroFlagWhenZero() throws MemoryAccessException {
         bus.loadProgram(0xca);
         cpu.setXRegister(0x01);
@@ -207,6 +217,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_DEX_SetsNegativeFlagWhen() throws MemoryAccessException {
         bus.loadProgram(0xca);
         cpu.step();
@@ -215,8 +226,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
-  /* DEY - Decrement the Y register - $88 */
+    /* DEY - Decrement the Y register - $88 */
-
+    @Test
     public void test_DEY() throws MemoryAccessException {
         bus.loadProgram(0x88);
         cpu.setYRegister(0x02);
@@ -226,6 +237,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_DEY_SetsZeroFlagWhenZero() throws MemoryAccessException {
         bus.loadProgram(0x88);
         cpu.setYRegister(0x01);
@@ -235,6 +247,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_DEY_SetsNegativeFlagWhen() throws MemoryAccessException {
         bus.loadProgram(0x88);
         cpu.step();
@@ -243,8 +256,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
-  /* INX - Increment the X register - $e8 */
+    /* INX - Increment the X register - $e8 */
-
+    @Test
     public void test_INX() throws MemoryAccessException {
         bus.loadProgram(0xe8);
         cpu.step();
@@ -253,6 +266,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_INX_SetsNegativeFlagWhenNegative() throws MemoryAccessException {
         bus.loadProgram(0xe8);
         cpu.setXRegister(0x7f);
@@ -262,6 +276,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_INX_SetsZeroFlagWhenZero() throws MemoryAccessException {
         bus.loadProgram(0xe8);
         cpu.setXRegister(0xff);
@@ -271,8 +286,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
-  /* INY - Increment the Y register - $c8 */
+    /* INY - Increment the Y register - $c8 */
-
+    @Test
     public void test_INY() throws MemoryAccessException {
         bus.loadProgram(0xc8);
         cpu.step();
@@ -281,6 +296,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_INY_SetsNegativeFlagWhenNegative() throws MemoryAccessException {
         bus.loadProgram(0xc8);
         cpu.setYRegister(0x7f);
@@ -290,6 +306,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_INY_SetsZeroFlagWhenZero() throws MemoryAccessException {
         bus.loadProgram(0xc8);
         cpu.setYRegister(0xff);
@@ -299,8 +316,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
-  /* NOP - No Operation - $ea */
+    /* NOP - No Operation - $ea */
-
+    @Test
     public void test_NOP() throws MemoryAccessException {
         bus.loadProgram(0xea);
         cpu.step();
@@ -313,8 +330,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertEquals(0x20, cpu.getProcessorStatus());
     }
 
-  /* PHA - Push Accumulator - $48 */
+    /* PHA - Push Accumulator - $48 */
-
+    @Test
     public void test_PHA() throws MemoryAccessException {
         bus.loadProgram(0x48);
         cpu.setAccumulator(0x3a);
@@ -323,18 +340,20 @@ public class CpuImpliedModeTest extends TestCase {
         assertEquals(0x3a, cpu.stackPeek());
     }
 
-  /* PHP - Push Processor Status - $08 */
+    /* PHP - Push Processor Status - $08 */
-
+    @Test
     public void test_PHP() throws MemoryAccessException {
         bus.loadProgram(0x08);
         cpu.setProcessorStatus(0x27);
         cpu.step();
         assertEquals(0xfe, cpu.getStackPointer());
-        assertEquals(0x27, cpu.stackPeek());
+        // PHP should have set the BREAK flag _on the stack_ (but not in the CPU)
+        assertEquals(0x37, cpu.stackPeek());
+        assertEquals(0x27, cpu.getProcessorStatus());
     }
 
-  /* PLA - Pul Accumulator - $68 */
+    /* PLA - Pul Accumulator - $68 */
-
+    @Test
     public void test_PLA() throws MemoryAccessException {
         cpu.stackPush(0x32);
         bus.loadProgram(0x68);
@@ -344,6 +363,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getZeroFlag());
     }
 
+    @Test
     public void test_PLA_SetsZeroIfAccumulatorIsZero() throws MemoryAccessException {
         cpu.stackPush(0x00);
         bus.loadProgram(0x68);
@@ -353,6 +373,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getZeroFlag());
     }
 
+    @Test
     public void test_PLA_SetsNegativeIfAccumulatorIsNegative() throws MemoryAccessException {
         cpu.stackPush(0xff);
         bus.loadProgram(0x68);
@@ -362,8 +383,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getZeroFlag());
     }
 
-  /* PLP - Pull Processor Status - $28 */
+    /* PLP - Pull Processor Status - $28 */
-
+    @Test
     public void test_PLP() throws MemoryAccessException {
         cpu.stackPush(0x2f);
         bus.loadProgram(0x28);
@@ -371,8 +392,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertEquals(0x2f, cpu.getProcessorStatus());
     }
 
-  /* RTI - Return from Interrupt - $40 */
+    /* RTI - Return from Interrupt - $40 */
-
+    @Test
     public void test_RTI() throws MemoryAccessException {
         cpu.stackPush(0x0f); // PC hi
         cpu.stackPush(0x11); // PC lo
@@ -385,8 +406,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertEquals(0x29, cpu.getProcessorStatus());
     }
 
-  /* RTS - Return from Subroutine - $60 */
+    /* RTS - Return from Subroutine - $60 */
-
+    @Test
     public void test_RTS() throws MemoryAccessException {
         cpu.stackPush(0x0f); // PC hi
         cpu.stackPush(0x11); // PC lo
@@ -398,32 +419,32 @@ public class CpuImpliedModeTest extends TestCase {
         assertEquals(0x20, cpu.getProcessorStatus());
     }
 
-  /* SEC - Set Carry Flag - $38 */
+    /* SEC - Set Carry Flag - $38 */
-
+    @Test
     public void test_SEC() throws MemoryAccessException {
         bus.loadProgram(0x38);
         cpu.step();
         assertTrue(cpu.getCarryFlag());
     }
 
-  /* SED - Set Decimal Mode Flag - $f8 */
+    /* SED - Set Decimal Mode Flag - $f8 */
-
+    @Test
     public void test_SED() throws MemoryAccessException {
         bus.loadProgram(0xf8);
         cpu.step();
         assertTrue(cpu.getDecimalModeFlag());
     }
 
-  /* SEI - Set Interrupt Disable Flag - $78 */
+    /* SEI - Set Interrupt Disable Flag - $78 */
-
+    @Test
     public void test_SEI() throws MemoryAccessException {
         bus.loadProgram(0x78);
         cpu.step();
         assertTrue(cpu.getIrqDisableFlag());
     }
 
-  /* TAX - Transfer Accumulator to X Register - $aa */
+    /* TAX - Transfer Accumulator to X Register - $aa */
-
+    @Test
     public void test_TAX() throws MemoryAccessException {
         cpu.setAccumulator(0x32);
         bus.loadProgram(0xaa);
@@ -433,6 +454,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TAX_SetsZeroFlagIfXIsZero() throws MemoryAccessException {
         cpu.setAccumulator(0x00);
         bus.loadProgram(0xaa);
@@ -442,6 +464,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TAX_SetsNegativeFlagIfXIsNegative() throws MemoryAccessException {
         cpu.setAccumulator(0xff);
         bus.loadProgram(0xaa);
@@ -451,8 +474,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
-  /* TAY - Transfer Accumulator to Y Register - $a8 */
+    /* TAY - Transfer Accumulator to Y Register - $a8 */
-
+    @Test
     public void test_TAY() throws MemoryAccessException {
         cpu.setAccumulator(0x32);
         bus.loadProgram(0xa8);
@@ -462,6 +485,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TAY_SetsZeroFlagIfYIsZero() throws MemoryAccessException {
         cpu.setAccumulator(0x00);
         bus.loadProgram(0xa8);
@@ -471,6 +495,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TAY_SetsNegativeFlagIfYIsNegative() throws MemoryAccessException {
         cpu.setAccumulator(0xff);
         bus.loadProgram(0xa8);
@@ -480,8 +505,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
-  /* TSX - Transfer Stack Pointer to X Register - $ba */
+    /* TSX - Transfer Stack Pointer to X Register - $ba */
-
+    @Test
     public void test_TSX() throws MemoryAccessException {
         cpu.setStackPointer(0x32);
         bus.loadProgram(0xba);
@@ -491,6 +516,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TSX_SetsZeroFlagIfXIsZero() throws MemoryAccessException {
         cpu.setStackPointer(0x00);
         bus.loadProgram(0xba);
@@ -500,6 +526,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TSX_SetsNegativeFlagIfXIsNegative() throws MemoryAccessException {
         cpu.setStackPointer(0xff);
         bus.loadProgram(0xba);
@@ -509,8 +536,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
-  /* TXA - Transfer X Register to Accumulator - $8a */
+    /* TXA - Transfer X Register to Accumulator - $8a */
-
+    @Test
     public void test_TXA() throws MemoryAccessException {
         cpu.setXRegister(0x32);
         bus.loadProgram(0x8a);
@@ -520,6 +547,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TXA_SetsZeroFlagIfAccumulatorIsZero() throws MemoryAccessException {
         cpu.setXRegister(0x00);
         bus.loadProgram(0x8a);
@@ -529,6 +557,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TXA_SetsNegativeFlagIfAccumulatorIsNegative() throws MemoryAccessException {
         cpu.setXRegister(0xff);
         bus.loadProgram(0x8a);
@@ -538,8 +567,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertTrue(cpu.getNegativeFlag());
     }
 
-  /* TXS - Transfer X Register to Stack Pointer - $9a */
+    /* TXS - Transfer X Register to Stack Pointer - $9a */
-
+    @Test
     public void test_TXS() throws MemoryAccessException {
         cpu.setXRegister(0x32);
         bus.loadProgram(0x9a);
@@ -549,6 +578,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TXS_DoesNotAffectProcessorStatus() throws MemoryAccessException {
         cpu.setXRegister(0x00);
         bus.loadProgram(0x9a);
@@ -565,8 +595,8 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
-  /* TYA - Transfer Y Register to Accumulator - $98 */
+    /* TYA - Transfer Y Register to Accumulator - $98 */
-
+    @Test
     public void test_TYA() throws MemoryAccessException {
         cpu.setYRegister(0x32);
         bus.loadProgram(0x98);
@@ -576,6 +606,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TYA_SetsZeroFlagIfAccumulatorIsZero() throws MemoryAccessException {
         cpu.setYRegister(0x00);
         bus.loadProgram(0x98);
@@ -585,6 +616,7 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getNegativeFlag());
     }
 
+    @Test
     public void test_TYA_SetsNegativeFlagIfAccumulatorIsNegative() throws MemoryAccessException {
         cpu.setYRegister(0xff);
         bus.loadProgram(0x98);
@@ -593,5 +625,4 @@ public class CpuImpliedModeTest extends TestCase {
         assertFalse(cpu.getZeroFlag());
         assertTrue(cpu.getNegativeFlag());
     }
-
 }

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

@@ -48,6 +48,32 @@ public class CpuIndexedIndirectModeTest {
         assertEquals(0x45, cpu.getAccumulator());
     }
 
+    @Test
+    public void testZeroPageWrap() throws Exception {
+        bus.write(0x0020, 0x01);
+        bus.write(0x0021, 0x07); // ($0701)
+        bus.write(0x0701, 0xaa);
+
+        bus.write(0x000f, 0x02);
+        bus.write(0x0010, 0x08); // ($0802)
+        bus.write(0x0802, 0xbb);
+
+        bus.write(0x010f, 0x03);
+        bus.write(0x0110, 0x09); // ($0903)
+        bus.write(0x0903, 0xcc);
+
+        cpu.setXRegister(0x10);
+
+        // No wrap needed
+        bus.loadProgram(0xa1, 0x10,  // LDA ($10,X) = ($10 + $10) & $ff =  $20
+                        0xa1, 0xff); // LDA ($ff,X) = ($ff + $10) & $ff =  $0f, NOT $10f!
+        cpu.step(1);
+        assertEquals(0xaa, cpu.getAccumulator());
+
+        cpu.step(1);
+        assertEquals(0xbb, cpu.getAccumulator());
+    }
+
     @Test
     public void test_ORA() throws Exception {
         bus.write(0x0012, 0x1f);