diff --git a/se/sics/mspsim/cli/DebugCommands.java b/se/sics/mspsim/cli/DebugCommands.java
index d95c936..91a0d71 100644
--- a/se/sics/mspsim/cli/DebugCommands.java
+++ b/se/sics/mspsim/cli/DebugCommands.java
@@ -206,7 +206,7 @@ public class DebugCommands implements CommandBundle {
           }
           monitor = new RegisterMonitor.Adapter() {
             @Override
-            public void notifyWriteBefore(int register, int data, int mode) {
+            public void notifyWriteBefore(int register, int data, AccessMode mode) {
                 if (watchMode == 0) {
                     int pc = cpu.getPC();
                     String adrStr = getRegisterName(register);
diff --git a/se/sics/mspsim/core/MSP430Core.java b/se/sics/mspsim/core/MSP430Core.java
index c62fdd0..a726064 100644
--- a/se/sics/mspsim/core/MSP430Core.java
+++ b/se/sics/mspsim/core/MSP430Core.java
@@ -438,9 +438,9 @@ public class MSP430Core extends Chip implements MSP430Constants {
     RegisterMonitor rwm = regWriteMonitors[r];
     if (rwm != null) {
         // TODO Add register access mode
-        rwm.notifyWriteBefore(r, value, 0);
+        rwm.notifyWriteBefore(r, value, AccessMode.WORD);
         reg[r] = value;
-        rwm.notifyWriteAfter(r, value, 0);
+        rwm.notifyWriteAfter(r, value, AccessMode.WORD);
     } else {
         reg[r] = value;
     }
@@ -493,9 +493,9 @@ public class MSP430Core extends Chip implements MSP430Constants {
     RegisterMonitor rrm = regReadMonitors[r];
     if (rrm != null) {
         // TODO Register access mode
-        rrm.notifyReadBefore(r, 0);
+        rrm.notifyReadBefore(r, AccessMode.WORD);
         value = reg[r];
-        rrm.notifyReadAfter(r, 0);
+        rrm.notifyReadAfter(r, AccessMode.WORD);
     } else {
         value = reg[r];
     }
@@ -512,9 +512,9 @@ public class MSP430Core extends Chip implements MSP430Constants {
     RegisterMonitor rrm = regReadMonitors[r];
     if (rrm != null) {
         // TODO Register access mode
-        rrm.notifyReadBefore(r, 0);
+        rrm.notifyReadBefore(r, AccessMode.WORD);
         value = reg[r];
-        rrm.notifyReadAfter(r, 0);
+        rrm.notifyReadAfter(r, AccessMode.WORD);
     } else {
         value = reg[r];
     }
@@ -525,18 +525,18 @@ public class MSP430Core extends Chip implements MSP430Constants {
     int registerValue;
     RegisterMonitor rm = regReadMonitors[r];
     if (rm != null) {
-        rm.notifyReadBefore(r, 0);
+        rm.notifyReadBefore(r, AccessMode.WORD);
         registerValue = reg[r];
-        rm.notifyReadAfter(r, 0);
+        rm.notifyReadAfter(r, AccessMode.WORD);
     } else {
         registerValue = reg[r];
     }
     rm = regWriteMonitors[r];
     registerValue += value;
     if (rm != null) {
-      rm.notifyWriteBefore(r, registerValue, 0);
+      rm.notifyWriteBefore(r, registerValue, AccessMode.WORD);
       reg[r] = registerValue;
-      rm.notifyWriteAfter(r, registerValue, 0);
+      rm.notifyWriteAfter(r, registerValue, AccessMode.WORD);
     } else {
       reg[r] = registerValue;
     }
diff --git a/se/sics/mspsim/core/RegisterMonitor.java b/se/sics/mspsim/core/RegisterMonitor.java
index 9d44ce9..b49fc3c 100644
--- a/se/sics/mspsim/core/RegisterMonitor.java
+++ b/se/sics/mspsim/core/RegisterMonitor.java
@@ -4,28 +4,28 @@ import se.sics.mspsim.util.ProxySupport;
 
 public interface RegisterMonitor {
 
-    public void notifyReadBefore(int reg, int mode);
-    public void notifyReadAfter(int reg, int mode);
+    public void notifyReadBefore(int reg, Memory.AccessMode mode);
+    public void notifyReadAfter(int reg, Memory.AccessMode mode);
 
-    public void notifyWriteBefore(int reg, int data, int mode);
-    public void notifyWriteAfter(int reg, int data, int mode);
+    public void notifyWriteBefore(int reg, int data, Memory.AccessMode mode);
+    public void notifyWriteAfter(int reg, int data, Memory.AccessMode mode);
 
     public static class Adapter implements RegisterMonitor {
 
         @Override
-        public void notifyReadBefore(int reg, int mode) {
+        public void notifyReadBefore(int reg, Memory.AccessMode mode) {
         }
 
         @Override
-        public void notifyReadAfter(int reg, int mode) {
+        public void notifyReadAfter(int reg, Memory.AccessMode mode) {
         }
 
         @Override
-        public void notifyWriteBefore(int reg, int data, int mode) {
+        public void notifyWriteBefore(int reg, int data, Memory.AccessMode mode) {
         }
 
         @Override
-        public void notifyWriteAfter(int reg, int data, int mode) {
+        public void notifyWriteAfter(int reg, int data, Memory.AccessMode mode) {
         }
 
     }
@@ -34,7 +34,7 @@ public interface RegisterMonitor {
         public static final Proxy INSTANCE = new Proxy();
 
         @Override
-        public void notifyReadBefore(int reg, int mode) {
+        public void notifyReadBefore(int reg, Memory.AccessMode mode) {
             RegisterMonitor[] listeners = this.listeners;
             for(RegisterMonitor listener : listeners) {
                 listener.notifyReadBefore(reg, mode);
@@ -42,7 +42,7 @@ public interface RegisterMonitor {
         }
 
         @Override
-        public void notifyReadAfter(int reg, int mode) {
+        public void notifyReadAfter(int reg, Memory.AccessMode mode) {
             RegisterMonitor[] listeners = this.listeners;
             for(RegisterMonitor listener : listeners) {
                 listener.notifyReadAfter(reg, mode);
@@ -50,7 +50,7 @@ public interface RegisterMonitor {
         }
 
         @Override
-        public void notifyWriteBefore(int reg, int data, int mode) {
+        public void notifyWriteBefore(int reg, int data, Memory.AccessMode mode) {
             RegisterMonitor[] listeners = this.listeners;
             for(RegisterMonitor listener : listeners) {
                 listener.notifyWriteBefore(reg, data, mode);
@@ -58,7 +58,7 @@ public interface RegisterMonitor {
         }
 
         @Override
-        public void notifyWriteAfter(int reg, int data, int mode) {
+        public void notifyWriteAfter(int reg, int data, Memory.AccessMode mode) {
             RegisterMonitor[] listeners = this.listeners;
             for(RegisterMonitor listener : listeners) {
                 listener.notifyWriteAfter(reg, data, mode);
diff --git a/se/sics/mspsim/ui/StackUI.java b/se/sics/mspsim/ui/StackUI.java
index 2bd6324..366b22d 100644
--- a/se/sics/mspsim/ui/StackUI.java
+++ b/se/sics/mspsim/ui/StackUI.java
@@ -45,6 +45,7 @@ import javax.swing.JPanel;
 
 import se.sics.mspsim.core.MSP430;
 import se.sics.mspsim.core.RegisterMonitor;
+import se.sics.mspsim.core.Memory.AccessMode;
 import se.sics.mspsim.util.ComponentRegistry;
 import se.sics.mspsim.util.MapTable;
 import se.sics.mspsim.util.ServiceComponent;
@@ -148,7 +149,7 @@ public class StackUI extends JPanel implements ServiceComponent {
 
       registerMonitor = new RegisterMonitor.Adapter() {
           @Override
-          public void notifyWriteBefore(int register, int data, int mode) {
+          public void notifyWriteBefore(int register, int data, AccessMode mode) {
               int size = stackStartAddress - data;
               if (minData[pos] > size) {
                   minData[pos] = size;
diff --git a/se/sics/mspsim/util/StackMonitor.java b/se/sics/mspsim/util/StackMonitor.java
index bc3d445..bc01294 100644
--- a/se/sics/mspsim/util/StackMonitor.java
+++ b/se/sics/mspsim/util/StackMonitor.java
@@ -1,6 +1,7 @@
 package se.sics.mspsim.util;
 import se.sics.mspsim.core.MSP430;
 import se.sics.mspsim.core.RegisterMonitor;
+import se.sics.mspsim.core.Memory.AccessMode;
 
 public class StackMonitor {
 
@@ -61,7 +62,7 @@ public class StackMonitor {
     cpu.addRegisterWriteMonitor(MSP430.SP, new RegisterMonitor.Adapter() {
 
         @Override
-        public void notifyWriteBefore(int reg, int data, int mode) {
+        public void notifyWriteBefore(int reg, int data, AccessMode mode) {
             // TODO add support for 20 bit addresses
             stack = ((stackStartAddress - data) + 0xffff) & 0xffff;
             if (stack > stackMax) {