diff --git a/src/main/java/de/neemann/digital/hdl/hgs/Value.java b/src/main/java/de/neemann/digital/hdl/hgs/Value.java
index 89ec76137..f9a843e96 100644
--- a/src/main/java/de/neemann/digital/hdl/hgs/Value.java
+++ b/src/main/java/de/neemann/digital/hdl/hgs/Value.java
@@ -125,6 +125,8 @@ public final class Value {
     public static boolean equals(Object a, Object b) {
         if (a instanceof Number && b instanceof Number)
             return ((Number) a).longValue() == ((Number) b).longValue();
+        else if (a instanceof String || b instanceof String)
+            return a.toString().equals(b.toString());
         else
             return a.equals(b);
     }
diff --git a/src/main/java/de/neemann/digital/hdl/vhdl2/VHDLCreator.java b/src/main/java/de/neemann/digital/hdl/vhdl2/VHDLCreator.java
index dacfdb46b..0c1c6cd4b 100644
--- a/src/main/java/de/neemann/digital/hdl/vhdl2/VHDLCreator.java
+++ b/src/main/java/de/neemann/digital/hdl/vhdl2/VHDLCreator.java
@@ -187,12 +187,14 @@ public class VHDLCreator {
         int i = 0;
         for (HDLPort outPort : node.getOutputs()) {
             Splitter.Port sp = is.getPort(i++);
-            out.print(outPort.getNet().getName()).print(" <= ").print(source).print("(");
-            if (outPort.getBits() == 1)
-                out.print(sp.getPos());
-            else
-                out.print(sp.getPos() + sp.getBits() - 1).print(" downto ").print(sp.getPos());
-            out.println(");");
+            if (outPort.getNet() != null) {
+                out.print(outPort.getNet().getName()).print(" <= ").print(source).print("(");
+                if (outPort.getBits() == 1)
+                    out.print(sp.getPos());
+                else
+                    out.print(sp.getPos() + sp.getBits() - 1).print(" downto ").print(sp.getPos());
+                out.println(");");
+            }
         }
     }
 
diff --git a/src/main/resources/vhdl2/DIG_Demultiplexer.tem b/src/main/resources/vhdl2/DIG_Demultiplexer.tem
index d779959e8..849fc8417 100644
--- a/src/main/resources/vhdl2/DIG_Demultiplexer.tem
+++ b/src/main/resources/vhdl2/DIG_Demultiplexer.tem
@@ -8,24 +8,21 @@ USE ieee.std_logic_1164.all;
 
   outputs:=1<<elem.'Selector Bits';
 ?>
-
 entity <?=entityName?> is
-<? vhdl.beginGenericPort();?>
-  <? if (elem.Bits>1) { ?>
+  <?- if (elem.Bits>1) { ?>
   generic ( Bits : integer );<?  vhdl.registerGeneric("Bits");?>
-  <? } ?>
+  <?- } ?>
   port (
-    <? for (i:=0;i<outputs;i++) {?>
-    PORT_out_<?=i?>: out <?= vhdl.genericType(elem.Bits)?>;
-    <? } ?>
-    PORT_sel: in <?= vhdl.type(elem.'Selector Bits')?>;
-    PORT_in: in <?= vhdl.genericType(elem.Bits)?> );
-<? vhdl.endGenericPort();?>
+    <?- for (i:=0;i<outputs;i++) {?>
+    out_<?=i?>: out <?= vhdl.genericType(elem.Bits)?>;
+    <?- } ?>
+    sel: in <?= vhdl.type(elem.'Selector Bits')?>;
+    p_in: in <?= vhdl.genericType(elem.Bits)?> );
 end <?=entityName?>;
 
 architecture <?=entityName?>_arch of <?=entityName?> is
 begin
-<? for (i:=0;i<outputs;i++) {?>
-    PORT_out_<?=i?> <= PORT_in when PORT_sel = <?= vhdl.value(i,elem.'Selector Bits')?> else <?= vhdl.zero(elem.Bits)?>;
-<? } ?>
+<?- for (i:=0;i<outputs;i++) {?>
+    out_<?=i?> <= p_in when sel = <?= vhdl.value(i,elem.'Selector Bits')?> else <?= vhdl.zero(elem.Bits)?>;
+<?- } ?>
 end <?=entityName?>_arch;
diff --git a/src/main/resources/vhdl2/DIG_External.tem b/src/main/resources/vhdl2/DIG_External.tem
new file mode 100644
index 000000000..278a63a6c
--- /dev/null
+++ b/src/main/resources/vhdl2/DIG_External.tem
@@ -0,0 +1,8 @@
+<?=elem.Code;
+
+  entityName:=elem.Label;
+
+  if (elem.applicationType!="GHDL")
+    panic("only GHDL components are supported for VHDL export! Found: "+elem.applicationType);
+
+?>
\ No newline at end of file
diff --git a/src/test/java/de/neemann/digital/hdl/vhdl2/VHDLGeneratorTest.java b/src/test/java/de/neemann/digital/hdl/vhdl2/VHDLGeneratorTest.java
index bfd3efead..4c68799fb 100644
--- a/src/test/java/de/neemann/digital/hdl/vhdl2/VHDLGeneratorTest.java
+++ b/src/test/java/de/neemann/digital/hdl/vhdl2/VHDLGeneratorTest.java
@@ -32,25 +32,21 @@ import java.text.SimpleDateFormat;
 import java.util.ArrayList;
 import java.util.Date;
 
+import static de.neemann.digital.integration.TestExamples.check;
+
 public class VHDLGeneratorTest extends TestCase {
     private static final String GHDL = System.getProperty("ghdl", "ghdl");
     private int testBenches;
 
-    public void testSimple() throws Exception {
-        File file = new File(Resources.getRoot(), "dig/test/vhdl/reset.dig");
+    /*
+    public void testDebug() throws Exception {
+        File file = new File(Resources.getRoot(), "dig/hdl/splitter2.dig");
 
         ToBreakRunner br = new ToBreakRunner(file);
         System.out.println(new VHDLGenerator(br.getLibrary(), new CodePrinterStr(true)).export(br.getCircuit()));
 
-        try {
-            checkVHDLExport(file);
-        } catch (FileScanner.SkipAllException e) {
-            // if ghdl is not installed its also ok
-        } catch (Exception e) {
-            System.out.println(ExceptionWithOrigin.getOriginOf(e));
-            throw e;
-        }
-    }
+        checkVHDLExport(file);
+    }/**/
 
     public void testInSimulator() throws Exception {
         File examples = new File(Resources.getRoot(), "/dig/test/vhdl");
@@ -73,7 +69,48 @@ public class VHDLGeneratorTest extends TestCase {
         }
     }
 
+    public void testDistributedInSimulator() throws Exception {
+        File examples = new File(Resources.getRoot(), "../../main/dig/vhdl");
+        try {
+            int tested = new FileScanner(this::checkVHDLExport).noOutput().scan(examples);
+            assertEquals(1, tested);
+            assertEquals(1, testBenches);
+        } catch (FileScanner.SkipAllException e) {
+            // if ghdl is not installed its also ok
+        }
+    }
 
+    public void testProcessorInSimulator() throws Exception {
+        File file = new File(Resources.getRoot(), "../../main/dig/processor/VHDLExample.dig");
+        try {
+            checkVHDLExport(file);
+        } catch (FileScanner.SkipAllException e) {
+            // if ghdl is not installed its also ok
+        } catch (Exception e) {
+            System.out.println(ExceptionWithOrigin.getOriginOf(e));
+            throw e;
+        }
+    }
+
+    public void testGHDLInSimulator() throws Exception {
+        try {
+            ProcessStarter.start(null, GHDL, "--help");
+        } catch (IOException e) {
+            // ghdl is not installed, Ignore Test
+            return;
+        }
+
+        Settings.getInstance().getAttributes().set(Keys.SETTINGS_GHDL_PATH, new File(GHDL));
+
+        File source = new File(Resources.getRoot(), "dig/external/ghdl");
+
+        int tested = new FileScanner(f -> {
+            checkVHDLExport(f);
+            // check simulation in Digital
+            check(f);
+        }).noOutput().scan(source);
+        assertEquals(4, tested);
+    }
 
 
     private void checkVHDLExport(File file) throws PinException, NodeException, ElementNotFoundException, IOException, FileScanner.SkipAllException, HDLException, de.neemann.digital.hdl.model2.HDLException, HGSEvalException {