diff --git a/src/main/java/de/neemann/digital/core/Model.java b/src/main/java/de/neemann/digital/core/Model.java
index 59b032334..7de24b2ff 100644
--- a/src/main/java/de/neemann/digital/core/Model.java
+++ b/src/main/java/de/neemann/digital/core/Model.java
@@ -41,37 +41,41 @@ public class Model {
 
     public void doStep(boolean noise) throws NodeException {
         int counter = 0;
-        while (!nodesToUpdateNext.isEmpty()) {
-            version++;
-            // swap lists
-            ArrayList<Node> nl = nodesToUpdateNext;
-            nodesToUpdateNext = nodesToUpdateAct;
-            nodesToUpdateAct = nl;
-
-            nodesToUpdateNext.clear();
-
-            if (noise) {
-                Collections.shuffle(nodesToUpdateAct);
-                for (Node n : nodesToUpdateAct) {
-                    n.readInputs();
-                    n.writeOutputs();
-                }
-            } else {
-                for (Node n : nodesToUpdateAct) {
-                    n.readInputs();
-                }
-                for (Node n : nodesToUpdateAct) {
-                    n.writeOutputs();
-                }
-            }
+        while (!doMicroStep(noise)) {
+            if (listener != null)
+                listener.needsUpdate();
             if (counter++ > maxCounter) {
                 throw new NodeException("seemsToOscillate");
             }
-            if (listener != null)
-                listener.needsUpdate();
         }
     }
 
+    public boolean doMicroStep(boolean noise) throws NodeException {
+        version++;
+        // swap lists
+        ArrayList<Node> nl = nodesToUpdateNext;
+        nodesToUpdateNext = nodesToUpdateAct;
+        nodesToUpdateAct = nl;
+
+        nodesToUpdateNext.clear();
+
+        if (noise) {
+            Collections.shuffle(nodesToUpdateAct);
+            for (Node n : nodesToUpdateAct) {
+                n.readInputs();
+                n.writeOutputs();
+            }
+        } else {
+            for (Node n : nodesToUpdateAct) {
+                n.readInputs();
+            }
+            for (Node n : nodesToUpdateAct) {
+                n.writeOutputs();
+            }
+        }
+        return nodesToUpdateNext.isEmpty();
+    }
+
     public void init() throws NodeException {
         init(false);
     }
diff --git a/src/main/java/de/neemann/digital/gui/Main.java b/src/main/java/de/neemann/digital/gui/Main.java
index 24f39033b..ad481da78 100644
--- a/src/main/java/de/neemann/digital/gui/Main.java
+++ b/src/main/java/de/neemann/digital/gui/Main.java
@@ -3,6 +3,7 @@ package de.neemann.digital.gui;
 import com.thoughtworks.xstream.XStream;
 import com.thoughtworks.xstream.io.xml.PrettyPrintWriter;
 import com.thoughtworks.xstream.io.xml.StaxDriver;
+import de.neemann.digital.core.Listener;
 import de.neemann.digital.core.Model;
 import de.neemann.digital.core.PartDescription;
 import de.neemann.digital.core.basic.*;
@@ -121,14 +122,29 @@ public class Main extends JFrame implements ClosingWindowListener.ConfirmSave {
         JMenu run = new JMenu("Run");
         bar.add(run);
 
+        JCheckBox microStep = new JCheckBox("micro");
+
         ToolTipAction runModel = new ToolTipAction("Run") {
             @Override
             public void actionPerformed(ActionEvent e) {
                 try {
-                    ModelDescription m = new ModelDescription(circuitComponent.getCircuit());
-                    Model model = m.create(circuitComponent);
-                    model.init(true);
                     circuitComponent.setMode(CircuitComponent.Mode.running);
+                    ModelDescription m = new ModelDescription(circuitComponent.getCircuit());
+                    Model model = m.createModel(circuitComponent);
+                    if (microStep.isSelected()) {
+                        model.setListener(new Listener() {
+                            @Override
+                            public void needsUpdate() {
+                                circuitComponent.paintImmediately(circuitComponent.getVisibleRect());
+                                try {
+                                    Thread.sleep(2000);
+                                } catch (InterruptedException e1) {
+                                    e1.printStackTrace();
+                                }
+                            }
+                        });
+                    }
+                    model.init(true);
                 } catch (Exception e1) {
                     new ErrorMessage("error creating model").addCause(e1).show(Main.this);
                 }
@@ -142,6 +158,8 @@ public class Main extends JFrame implements ClosingWindowListener.ConfirmSave {
         toolBar.add(partsMode.createJButton());
         toolBar.add(wireMode.createJButton());
         toolBar.add(selectionMode.createJButton());
+        toolBar.add(runModel.createJButton());
+        toolBar.add(microStep);
 
         toolBar.addSeparator();
         insertHistory = new InsertHistory(toolBar);
diff --git a/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java b/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java
index 09cb4f0a7..919975bd1 100644
--- a/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java
+++ b/src/main/java/de/neemann/digital/gui/components/CircuitComponent.java
@@ -75,6 +75,7 @@ public class CircuitComponent extends JComponent implements Listener {
         addMouseMotionListener(listener);
         addMouseListener(listener);
         requestFocusInWindow();
+        circuit.clearState();
         repaint();
     }
 
diff --git a/src/main/java/de/neemann/digital/gui/draw/model/ModelDescription.java b/src/main/java/de/neemann/digital/gui/draw/model/ModelDescription.java
index 6d3f9afd8..fc1bbf14f 100644
--- a/src/main/java/de/neemann/digital/gui/draw/model/ModelDescription.java
+++ b/src/main/java/de/neemann/digital/gui/draw/model/ModelDescription.java
@@ -30,7 +30,7 @@ public class ModelDescription {
         }
     }
 
-    public Model create(Listener listener) throws PinException, NodeException {
+    public Model createModel(Listener listener) throws PinException, NodeException {
         for (Net n : netList)
             n.interconnect();
 
diff --git a/src/main/java/de/neemann/digital/gui/draw/parts/Circuit.java b/src/main/java/de/neemann/digital/gui/draw/parts/Circuit.java
index cebb05af7..a49a4900b 100644
--- a/src/main/java/de/neemann/digital/gui/draw/parts/Circuit.java
+++ b/src/main/java/de/neemann/digital/gui/draw/parts/Circuit.java
@@ -105,4 +105,11 @@ public class Circuit implements Drawable {
             dots = WireConsistencyChecker.createDots(wires);
         return dots;
     }
+
+    public void clearState() {
+        for (VisualPart vp : visualParts)
+            vp.setState(null, null, null);
+        for (Wire w : wires)
+            w.setValue(null);
+    }
 }
diff --git a/src/main/java/de/neemann/digital/gui/draw/parts/VisualPart.java b/src/main/java/de/neemann/digital/gui/draw/parts/VisualPart.java
index fc81b4ea3..a286229a0 100644
--- a/src/main/java/de/neemann/digital/gui/draw/parts/VisualPart.java
+++ b/src/main/java/de/neemann/digital/gui/draw/parts/VisualPart.java
@@ -132,7 +132,10 @@ public class VisualPart implements Drawable, Moveable {
      */
     public void setState(State state, Listener listener, Model model) {
         this.state = state;
-        interactor = partDescription.getShape().applyStateMonitor(state, listener, model);
+        if (state == null)
+            interactor = null;
+        else
+            interactor = partDescription.getShape().applyStateMonitor(state, listener, model);
     }
 
     public void clicked(CircuitComponent cc, Vector pos) {
diff --git a/src/main/java/de/neemann/digital/gui/draw/shapes/GenericShape.java b/src/main/java/de/neemann/digital/gui/draw/shapes/GenericShape.java
index 69e398ddd..4c21a4587 100644
--- a/src/main/java/de/neemann/digital/gui/draw/shapes/GenericShape.java
+++ b/src/main/java/de/neemann/digital/gui/draw/shapes/GenericShape.java
@@ -76,21 +76,6 @@ public class GenericShape implements Shape {
 
     @Override
     public Interactor applyStateMonitor(State state, Listener listener, Model model) {
-        if (symmetric) {
-            state.getOutput(0).addListener(new Listener() {
-                public long lastValue = 0;
-
-                @Override
-                public void needsUpdate() {
-                    long value = state.getInput(0).getValue();
-                    if (lastValue != value) {
-                        lastValue = value;
-                        listener.needsUpdate();
-                    }
-                }
-            });
-
-        }
         return null;
     }
 
@@ -99,9 +84,9 @@ public class GenericShape implements Shape {
         int max = Math.max(inputs, outputs);
         int height = (max - 1) * SIZE + SIZE2;
 
-        if (symmetric && state != null) {
-            graphic.drawText(new Vector(width * SIZE, 0), new Vector((width + 1) * SIZE, 0), Long.toString(state.getOutput(0).getValue()));
-        }
+//        if (symmetric && state != null) {
+//            graphic.drawText(new Vector(width * SIZE, 0), new Vector((width + 1) * SIZE, 0), Long.toString(state.getOutput(0).getValue()));
+//        }
 
 
         if (symmetric && ((inputs & 1) == 0)) height += SIZE;