diff --git a/src/main/java/com/loomcom/symon/Bus.java b/src/main/java/com/loomcom/symon/Bus.java
index 5ec836e..1b36044 100644
--- a/src/main/java/com/loomcom/symon/Bus.java
+++ b/src/main/java/com/loomcom/symon/Bus.java
@@ -76,8 +76,7 @@ public class Bus {
     }
     
     private void buildDeviceAddressArray() {
-        // TODO: Find out why +2 and not +1 is needed here
-        int size = (this.endAddress - this.startAddress) + 2;
+        int size = (this.endAddress - this.startAddress) + 1;
         deviceAddressArray = new Device[size];
         
         List<Integer> priorities = new ArrayList<Integer>(deviceMap.keySet());
@@ -88,7 +87,7 @@ public class Bus {
             for(Device device : deviceSet) {
                 MemoryRange range = device.getMemoryRange();
                 for(int address = range.startAddress; address <= range.endAddress; ++address) {
-                    deviceAddressArray[address] = device;
+                    deviceAddressArray[address - this.startAddress] = device;
                 }
             }
         }
@@ -101,7 +100,16 @@ public class Bus {
      * @param device
      * @param priority
      */
-    public void addDevice(Device device, int priority) {
+    public void addDevice(Device device, int priority) throws MemoryRangeException {
+        
+        MemoryRange range = device.getMemoryRange();
+        if(range.startAddress() < this.startAddress || range.startAddress() > this.endAddress) {
+            throw new MemoryRangeException("start address of device " + device.getName() + " does not fall within the address range of the bus");
+        }
+        if(range.endAddress() < this.startAddress || range.endAddress() > this.endAddress) {
+            throw new MemoryRangeException("end address of device " + device.getName() + " does not fall within the address range of the bus");
+        }
+  
         
         SortedSet<Device> deviceSet = deviceMap.get(priority);
         if(deviceSet == null) {
@@ -152,7 +160,7 @@ public class Bus {
         }
         
         for(int address = startAddress; address <= endAddress; ++address) {
-            if(deviceAddressArray[address] == null) {
+            if(deviceAddressArray[address - startAddress] == null) {
                 return false;
             }
         }
@@ -161,7 +169,7 @@ public class Bus {
     }
 
     public int read(int address) throws MemoryAccessException {
-        Device d = deviceAddressArray[address];
+        Device d = deviceAddressArray[address - this.startAddress];
         if(d != null) {
             MemoryRange range = d.getMemoryRange();
             int devAddr = address - range.startAddress();
@@ -172,7 +180,7 @@ public class Bus {
     }
 
     public void write(int address, int value) throws MemoryAccessException {
-        Device d = deviceAddressArray[address];
+        Device d = deviceAddressArray[address - this.startAddress];
         if(d != null) {
             MemoryRange range = d.getMemoryRange();
             int devAddr = address - range.startAddress();
diff --git a/src/test/java/com/loomcom/symon/CpuAbsoluteModeTest.java b/src/test/java/com/loomcom/symon/CpuAbsoluteModeTest.java
index ea63c58..6921492 100644
--- a/src/test/java/com/loomcom/symon/CpuAbsoluteModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuAbsoluteModeTest.java
@@ -14,7 +14,7 @@ public class CpuAbsoluteModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuAbsoluteXModeTest.java b/src/test/java/com/loomcom/symon/CpuAbsoluteXModeTest.java
index 842f4b2..958e959 100644
--- a/src/test/java/com/loomcom/symon/CpuAbsoluteXModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuAbsoluteXModeTest.java
@@ -14,7 +14,7 @@ public class CpuAbsoluteXModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuAbsoluteYModeTest.java b/src/test/java/com/loomcom/symon/CpuAbsoluteYModeTest.java
index 8521ab0..284bf29 100644
--- a/src/test/java/com/loomcom/symon/CpuAbsoluteYModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuAbsoluteYModeTest.java
@@ -14,7 +14,7 @@ public class CpuAbsoluteYModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuAccumulatorModeTest.java b/src/test/java/com/loomcom/symon/CpuAccumulatorModeTest.java
index f036b9c..7b51770 100644
--- a/src/test/java/com/loomcom/symon/CpuAccumulatorModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuAccumulatorModeTest.java
@@ -14,7 +14,7 @@ public class CpuAccumulatorModeTest extends TestCase {
     public void setUp() throws MemoryRangeException, MemoryAccessException {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuImmediateModeTest.java b/src/test/java/com/loomcom/symon/CpuImmediateModeTest.java
index 628a6ec..148106d 100644
--- a/src/test/java/com/loomcom/symon/CpuImmediateModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuImmediateModeTest.java
@@ -14,7 +14,7 @@ public class CpuImmediateModeTest extends TestCase {
     public void setUp() throws MemoryRangeException, MemoryAccessException {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuImpliedModeTest.java b/src/test/java/com/loomcom/symon/CpuImpliedModeTest.java
index ae3d141..8363646 100644
--- a/src/test/java/com/loomcom/symon/CpuImpliedModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuImpliedModeTest.java
@@ -17,7 +17,7 @@ public class CpuImpliedModeTest {
     public void setUp() throws MemoryRangeException, MemoryAccessException {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuIndexedIndirectModeTest.java b/src/test/java/com/loomcom/symon/CpuIndexedIndirectModeTest.java
index 346dd0c..5bf39b5 100644
--- a/src/test/java/com/loomcom/symon/CpuIndexedIndirectModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuIndexedIndirectModeTest.java
@@ -16,7 +16,7 @@ public class CpuIndexedIndirectModeTest {
     public void runBeforeEveryTest() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuIndirectIndexedModeTest.java b/src/test/java/com/loomcom/symon/CpuIndirectIndexedModeTest.java
index 1e2c543..191e930 100644
--- a/src/test/java/com/loomcom/symon/CpuIndirectIndexedModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuIndirectIndexedModeTest.java
@@ -16,7 +16,7 @@ public class CpuIndirectIndexedModeTest {
     public void runBeforeEveryTest() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuIndirectModeTest.java b/src/test/java/com/loomcom/symon/CpuIndirectModeTest.java
index 910cb45..87f7442 100644
--- a/src/test/java/com/loomcom/symon/CpuIndirectModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuIndirectModeTest.java
@@ -14,7 +14,7 @@ public class CpuIndirectModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuIndirectXModeTest.java b/src/test/java/com/loomcom/symon/CpuIndirectXModeTest.java
index 92fcdaa..15ad0ce 100644
--- a/src/test/java/com/loomcom/symon/CpuIndirectXModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuIndirectXModeTest.java
@@ -13,7 +13,7 @@ public class CpuIndirectXModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuRelativeModeTest.java b/src/test/java/com/loomcom/symon/CpuRelativeModeTest.java
index 9a5f0fe..325bcf3 100644
--- a/src/test/java/com/loomcom/symon/CpuRelativeModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuRelativeModeTest.java
@@ -14,7 +14,7 @@ public class CpuRelativeModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuTest.java b/src/test/java/com/loomcom/symon/CpuTest.java
index a44e92d..d7e7cb4 100644
--- a/src/test/java/com/loomcom/symon/CpuTest.java
+++ b/src/test/java/com/loomcom/symon/CpuTest.java
@@ -25,7 +25,7 @@ public class CpuTest extends TestCase {
     public void setUp() throws MemoryRangeException, MemoryAccessException {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuZeroPageModeTest.java b/src/test/java/com/loomcom/symon/CpuZeroPageModeTest.java
index 9ba2691..93ca971 100644
--- a/src/test/java/com/loomcom/symon/CpuZeroPageModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuZeroPageModeTest.java
@@ -14,7 +14,7 @@ public class CpuZeroPageModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuZeroPageXModeTest.java b/src/test/java/com/loomcom/symon/CpuZeroPageXModeTest.java
index b612d93..67d5f17 100644
--- a/src/test/java/com/loomcom/symon/CpuZeroPageXModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuZeroPageXModeTest.java
@@ -14,7 +14,7 @@ public class CpuZeroPageXModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);
 
diff --git a/src/test/java/com/loomcom/symon/CpuZeroPageYModeTest.java b/src/test/java/com/loomcom/symon/CpuZeroPageYModeTest.java
index ed23b98..e1ef721 100644
--- a/src/test/java/com/loomcom/symon/CpuZeroPageYModeTest.java
+++ b/src/test/java/com/loomcom/symon/CpuZeroPageYModeTest.java
@@ -14,7 +14,7 @@ public class CpuZeroPageYModeTest extends TestCase {
     protected void setUp() throws Exception {
         this.cpu = new Cpu();
         this.bus = new Bus(0x0000, 0xffff);
-        this.mem = new Memory(0x0000, 0x10000);
+        this.mem = new Memory(0x0000, 0xffff);
         bus.addCpu(cpu);
         bus.addDevice(mem);