diff --git a/src/db/db/dbLayoutToNetlistFormatDefs.h b/src/db/db/dbLayoutToNetlistFormatDefs.h
index 66cc393e1..5f261e467 100644
--- a/src/db/db/dbLayoutToNetlistFormatDefs.h
+++ b/src/db/db/dbLayoutToNetlistFormatDefs.h
@@ -58,7 +58,7 @@ namespace db
  *                                  - connects the shapes of the layer with the given global
  *                                    nets [short key: G]
  *    circuit(<name> [circuit-def]) - circuit (cell) [short key: X]
- *    class(<name> <template>)      - a device class definition (template: RES,CAP,...) [short key: K]
+ *    class(<name> <template> [template-def])  - a device class definition (template: RES,CAP,...) [short key: K]
  *    device(<name> <class> [device-abstract-def])
  *                                  - device abstract [short key: D]
  *
@@ -127,8 +127,18 @@ namespace db
  *    (<x> <y>)                     - relative coordinates (reference is reset to 0,0
  *                                    for each net or terminal in device abstract)
  *
+ *  [template-def]:
+ *
+ *    param(<name> <primary>? <default-value>*)    - defines a template parameter [short key: E]
+ *                                    ('primary' is a value: 0 or 1)
+ *    terminal(<name>)              - defines a terminal [short key: T]
+ *
  *  [device-abstract-def]:
  *
+ *    [device-abstract-terminal-def]*
+ *
+ *  [device-abstract-terminal-def]:
+ *
  *    terminal(<terminal-name> [geometry-def]*)
  *                                  - specifies the terminal geometry [short key: T]
  *
diff --git a/src/db/db/dbLayoutToNetlistReader.cc b/src/db/db/dbLayoutToNetlistReader.cc
index d809398d1..4300c0a43 100644
--- a/src/db/db/dbLayoutToNetlistReader.cc
+++ b/src/db/db/dbLayoutToNetlistReader.cc
@@ -236,10 +236,9 @@ void LayoutToNetlistStandardReader::read_netlist (db::Netlist *netlist, db::Layo
       std::string class_name, templ_name;
       read_word_or_quoted (class_name);
       read_word_or_quoted (templ_name);
-      br.done ();
 
       if (netlist->device_class_by_name (class_name) != 0) {
-        throw tl::Exception (tl::to_string (tr ("Device class must be defined before being used in device")));
+        throw tl::Exception (tl::to_string (tr ("Duplicate definition of device class: ")) + class_name);
       }
 
       db::DeviceClassTemplateBase *dct = db::DeviceClassTemplateBase::template_by_name (templ_name);
@@ -251,6 +250,52 @@ void LayoutToNetlistStandardReader::read_netlist (db::Netlist *netlist, db::Layo
       dc->set_name (class_name);
       netlist->add_device_class (dc);
 
+      while (br) {
+
+        if (test (skeys::terminal_key) || test (lkeys::terminal_key)) {
+
+          Brace br (this);
+
+          std::string terminal_name;
+          read_word_or_quoted (terminal_name);
+          if (! dc->has_terminal_with_name (terminal_name)) {
+            db::DeviceTerminalDefinition td;
+            td.set_name (terminal_name);
+            dc->add_terminal_definition (td);
+          }
+
+          br.done ();
+
+        } else if (test (skeys::param_key) || test (lkeys::param_key)) {
+
+          Brace br (this);
+
+          std::string param_name;
+          read_word_or_quoted (param_name);
+          int primary = read_int ();
+          int default_value = read_double ();
+          if (! dc->has_parameter_with_name (param_name)) {
+            db::DeviceParameterDefinition pd;
+            pd.set_name (param_name);
+            pd.set_is_primary (primary);
+            pd.set_default_value (default_value);
+            dc->add_parameter_definition (pd);
+          } else {
+            db::DeviceParameterDefinition *pd = dc->parameter_definition_non_const (dc->parameter_id_for_name (param_name));
+            pd->set_default_value (default_value);
+            pd->set_is_primary (primary);
+          }
+
+          br.done ();
+
+        } else {
+          throw tl::Exception (tl::to_string (tr ("Invalid keyword")));
+        }
+
+      }
+
+      br.done ();
+
     } else if (l2n && (test (skeys::connect_key) || test (lkeys::connect_key))) {
 
       Brace br (this);
diff --git a/src/db/db/dbLayoutToNetlistWriter.cc b/src/db/db/dbLayoutToNetlistWriter.cc
index 4dc227ae4..d7956761d 100644
--- a/src/db/db/dbLayoutToNetlistWriter.cc
+++ b/src/db/db/dbLayoutToNetlistWriter.cc
@@ -24,6 +24,7 @@
 #include "dbLayoutToNetlist.h"
 #include "dbLayoutToNetlistFormatDefs.h"
 #include "dbPolygonTools.h"
+#include "tlMath.h"
 
 namespace db
 {
@@ -113,6 +114,47 @@ void std_writer_impl<Keys>::write (const db::Netlist *netlist, const db::LayoutT
   }
 }
 
+static bool same_parameter (const DeviceParameterDefinition &a, const DeviceParameterDefinition &b)
+{
+  if (a.is_primary () != b.is_primary ()) {
+    return false;
+  }
+  if (! tl::equal (a.default_value (), b.default_value ())) {
+    return false;
+  }
+  return true;
+}
+
+template <class Keys>
+void std_writer_impl<Keys>::write_device_class (const std::string &indent, const db::DeviceClass *cls, const std::string &temp_name, const db::DeviceClass *temp_class)
+{
+  *mp_stream << indent << Keys::class_key << "(" << tl::to_word_or_quoted_string (cls->name ()) << " " << tl::to_word_or_quoted_string (temp_name);
+
+  bool any_def = false;
+
+  const std::vector<DeviceParameterDefinition> &pd = cls->parameter_definitions ();
+  for (std::vector<DeviceParameterDefinition>::const_iterator p = pd.begin (); p != pd.end (); ++p) {
+    if (! temp_class->has_parameter_with_name (p->name ()) || !same_parameter (*p, *temp_class->parameter_definition (temp_class->parameter_id_for_name (p->name ())))) {
+      *mp_stream << endl << indent << indent1 << Keys::param_key << "(" << tl::to_word_or_quoted_string (p->name ()) << " " << tl::to_string (p->is_primary () ? 1 : 0) << " " << tl::to_string (p->default_value ()) << ")";
+      any_def = true;
+    }
+  }
+
+  const std::vector<DeviceTerminalDefinition> &td = cls->terminal_definitions ();
+  for (std::vector<DeviceTerminalDefinition>::const_iterator t = td.begin (); t != td.end (); ++t) {
+    if (! temp_class->has_terminal_with_name (t->name ())) {
+      *mp_stream << endl << indent << indent1 << Keys::terminal_key << "(" << tl::to_word_or_quoted_string (t->name ()) << ")";
+      any_def = true;
+    }
+  }
+
+  if (any_def) {
+    *mp_stream << endl << indent << ")" << endl;
+  } else {
+    *mp_stream << ")" << endl;
+  }
+}
+
 template <class Keys>
 void std_writer_impl<Keys>::write (bool nested, std::map<const db::Circuit *, std::map<const db::Net *, unsigned int> > *net2id_per_circuit)
 {
@@ -203,9 +245,13 @@ void std_writer_impl<Keys>::write (bool nested, std::map<const db::Circuit *, st
   for (db::Netlist::const_device_class_iterator c = mp_netlist->begin_device_classes (); c != mp_netlist->end_device_classes (); ++c) {
     db::DeviceClassTemplateBase *temp = db::DeviceClassTemplateBase::is_a (c.operator-> ());
     if (temp) {
-      *mp_stream << indent << Keys::class_key << "(" << tl::to_word_or_quoted_string (c->name ()) << " " << tl::to_word_or_quoted_string (temp->name ()) << ")" << endl;
-      m_progress.set (mp_stream->pos ());
+      std::unique_ptr<db::DeviceClass> temp_class (temp->create ());
+      write_device_class (indent, c.operator-> (), temp->name (), temp_class.get ());
+    } else {
+      db::DeviceClass empty;
+      write_device_class (indent, c.operator-> (), std::string (), &empty);
     }
+    m_progress.set (mp_stream->pos ());
   }
 
   if (mp_netlist->begin_device_abstracts () != mp_netlist->end_device_abstracts () && ! Keys::is_short ()) {
diff --git a/src/db/db/dbLayoutToNetlistWriter.h b/src/db/db/dbLayoutToNetlistWriter.h
index 72d9b14f8..67d2b0366 100644
--- a/src/db/db/dbLayoutToNetlistWriter.h
+++ b/src/db/db/dbLayoutToNetlistWriter.h
@@ -37,6 +37,7 @@ namespace db
 class Circuit;
 class SubCircuit;
 class Device;
+class DeviceClass;
 class DeviceAbstract;
 class Net;
 class Netlist;
@@ -78,6 +79,7 @@ private:
   void write (const db::DeviceAbstract &device_abstract, const std::string &indent);
   void write (const db::NetShape *s, const db::ICplxTrans &tr, const std::string &lname, bool relative);
   void write (const db::DCplxTrans &trans);
+  void write_device_class (const std::string &indent, const db::DeviceClass *cls, const std::string &name, const db::DeviceClass *temp_class);
   void reset_geometry_ref ();
 
   //  implementation of CircuitCallback