diff --git a/src/main/java/de/neemann/digital/core/IntFormat.java b/src/main/java/de/neemann/digital/core/IntFormat.java
index fc87c0a69..4cf195f98 100644
--- a/src/main/java/de/neemann/digital/core/IntFormat.java
+++ b/src/main/java/de/neemann/digital/core/IntFormat.java
@@ -138,6 +138,11 @@ public enum IntFormat {
         public long dragValue(long initial, int bits, double inc) {
             return dragValueSigned(initial, bits, inc, false);
         }
+
+        @Override
+        public IsSeparator getSeparators(int bits) {
+            return bit -> bit % 4 == 0;
+        }
     }
 
     private static long dragValueSigned(long initial, int bits, double inc, boolean signed) {
@@ -224,6 +229,11 @@ public enum IntFormat {
         public int strLen(int bits) {
             return (bits - 1) / 4 + 3;
         }
+
+        @Override
+        public IsSeparator getSeparators(int bits) {
+            return bit -> bit % 4 == 0;
+        }
     }
 
     /**
@@ -289,6 +299,11 @@ public enum IntFormat {
             }
             return sb.toString();
         }
+
+        @Override
+        public IsSeparator getSeparators(int bits) {
+            return bit -> bit % 3 == 0;
+        }
     }
 
     /**
@@ -448,6 +463,11 @@ public enum IntFormat {
         public long dragValue(long initial, int bits, double inc) {
             return dragValueSigned(initial, bits, inc, signed);
         }
+
+        @Override
+        public IsSeparator getSeparators(int bits) {
+            return bit -> bit == fixedPoint;
+        }
     }
 
     /**
@@ -527,6 +547,18 @@ public enum IntFormat {
             else
                 return Double.doubleToLongBits(val);
         }
+
+        @Override
+        public IsSeparator getSeparators(int bits) {
+            switch (bits) {
+                case 32:
+                    return bit -> bit == 31 || bit == 23;
+                case 64:
+                    return bit -> bit == 63 || bit == 52;
+                default:
+                    return HEX_FORMATTER.getSeparators(bits);
+            }
+        }
     }
 
 }
diff --git a/src/main/java/de/neemann/digital/core/ValueFormatter.java b/src/main/java/de/neemann/digital/core/ValueFormatter.java
index 5a7339d35..10584c76d 100644
--- a/src/main/java/de/neemann/digital/core/ValueFormatter.java
+++ b/src/main/java/de/neemann/digital/core/ValueFormatter.java
@@ -54,4 +54,28 @@ public interface ValueFormatter {
      * @return the modified value
      */
     long dragValue(long initial, int bits, double inc);
+
+    /**
+     * Returns the {@link IsSeparator} interface to place separators in the {@link de.neemann.digital.gui.components.SingleValueDialog}
+     * Defaults to no separator at all.
+     *
+     * @param bits the number of bits used
+     * @return the IsSeparator instance
+     */
+    default IsSeparator getSeparators(int bits) {
+        return bit -> false;
+    }
+
+    /**
+     * Interface to define separators
+     */
+    interface IsSeparator {
+        /**
+         * Returns true if there should be a separator in front of the given bit.
+         *
+         * @param bit the bit in question
+         * @return true if there should be a separator in front of the given bit.
+         */
+        boolean isSeparatorInFrontOf(int bit);
+    }
 }
diff --git a/src/main/java/de/neemann/digital/gui/components/SingleValueDialog.java b/src/main/java/de/neemann/digital/gui/components/SingleValueDialog.java
index 5c4dd8dc1..5ef5f2a13 100644
--- a/src/main/java/de/neemann/digital/gui/components/SingleValueDialog.java
+++ b/src/main/java/de/neemann/digital/gui/components/SingleValueDialog.java
@@ -11,6 +11,7 @@ import de.neemann.digital.lang.Lang;
 import de.neemann.gui.Screen;
 
 import javax.swing.*;
+import javax.swing.border.Border;
 import javax.swing.event.ChangeListener;
 import javax.swing.event.DocumentEvent;
 import javax.swing.event.DocumentListener;
@@ -28,6 +29,7 @@ import java.util.ArrayList;
 public final class SingleValueDialog extends JDialog implements ModelStateObserverTyped {
 
     private static final Format[] FORMATS;
+    private static final Border SEPARATOR = BorderFactory.createEmptyBorder(0, 0, 0, 5);
 
     static {
         ArrayList<Format> f = new ArrayList<>();
@@ -98,8 +100,10 @@ public final class SingleValueDialog extends JDialog implements ModelStateObserv
         formatComboBox = new JComboBox<>(FORMATS);
         formatComboBox.addActionListener(actionEvent -> {
             Format selectedItem = (Format) formatComboBox.getSelectedItem();
-            if (selectedItem != null)
+            if (selectedItem != null) {
                 valueFormatter = selectedItem.intFormat.createFormatter(null);
+                updateSeparators();
+            }
             setLongToDialog(editValue);
         });
 
@@ -205,6 +209,7 @@ public final class SingleValueDialog extends JDialog implements ModelStateObserv
             checkBoxes[bit].addActionListener(actionEvent -> setBit(bit, checkBoxes[bit].isSelected()));
             p.add(checkBoxes[bit]);
         }
+        updateSeparators();
         return p;
     }
 
@@ -234,10 +239,22 @@ public final class SingleValueDialog extends JDialog implements ModelStateObserv
         valueFormatter = format;
         formatComboBox.setSelectedItem(findFormat(valueFormatter));
         setLongToDialog(editValue);
+        updateSeparators();
         requestFocus();
         return this;
     }
 
+    private void updateSeparators() {
+        ValueFormatter.IsSeparator s = valueFormatter.getSeparators(editValue.getBits());
+        for (int i = 1; i < checkBoxes.length; i++) {
+            if (s.isSeparatorInFrontOf(i))
+                checkBoxes[i].setBorder(SEPARATOR);
+            else
+                checkBoxes[i].setBorder(null);
+        }
+        pack();
+    }
+
     private void setStringToDialog(String text) {
         text = text.trim();
         if (text.equalsIgnoreCase("z") && supportsHighZ)