diff --git a/scripts/python-skywater-pdk/skywater_pdk/cells/generate/vcd2wavedrom.py b/scripts/python-skywater-pdk/skywater_pdk/cells/generate/vcd2wavedrom.py
index 69f3ef4..ed9b43b 100755
--- a/scripts/python-skywater-pdk/skywater_pdk/cells/generate/vcd2wavedrom.py
+++ b/scripts/python-skywater-pdk/skywater_pdk/cells/generate/vcd2wavedrom.py
@@ -75,8 +75,11 @@
                 currtag = 'body'    
                 vcd[currtag] = ''
 
-    if 'var' not in vcd or 'dumpvars' not in vcd:
-      raise SyntaxError("Invalid VCD file format")
+    if 'var' not in vcd:
+      raise SyntaxError("No variables recorded in VCD file")
+    if 'dumpvars' not in vcd:
+      print ("Warning: intial variable states undefined")
+      var['dumpvars'] = ''
 
     return vcd
 
@@ -213,9 +216,8 @@
                 svg.saveas(outfile)
         except KeyboardInterrupt:
             sys.exit(1)
-        except (AssertionError, FileNotFoundError, ChildProcessError) as ex:
-            eprint (f'Error: {type(ex).__name__}')
-            eprint (f'{ex.args}')
+        except (SyntaxError, AssertionError, FileNotFoundError, ChildProcessError) as ex:
+            eprint (f'{type(ex).__name__}: {", ".join(ex.args)}')
             errors +=1
     eprint (f'\n{len(infile)} files processed, {errors} errors.')
     return 0 if errors else 1
diff --git a/scripts/python-skywater-pdk/skywater_pdk/cells/generate/waveform.py b/scripts/python-skywater-pdk/skywater_pdk/cells/generate/waveform.py
index ec3b865..a21d2ad 100755
--- a/scripts/python-skywater-pdk/skywater_pdk/cells/generate/waveform.py
+++ b/scripts/python-skywater-pdk/skywater_pdk/cells/generate/waveform.py
@@ -49,6 +49,8 @@
     testbedfile = os.path.join(cellpath, define_data['file_prefix'] + '.tb.v')
     assert os.path.exists(testbedfile), testbedfile
     insertppdefine = use_power_pins
+    insertdumpvars = True
+    insertfinish   = True
     prvline=''
     with open(tmptestbed,'w') as ttb:
         with open(testbedfile,'r') as tbf:
@@ -58,12 +60,17 @@
                     line = '`define USE_POWER_PINS\n' + line
                     insertppdefine = False 
                 # add dumpfile define                 
-                if prvline.strip(' \n\r')=='begin':
+                if insertdumpvars and prvline.strip(' \n\r')=='begin':
                     line = line[:-len(line.lstrip())] + \
                            '$dumpfile("' + outfile + '");\n' + \
                            line[:-len(line.lstrip())] + \
                            '$dumpvars(1,top);\n' + \
                            line
+                    insertdumpvars = False
+                # add finish command, to stop paraller threads
+                if insertfinish and line.strip(' \n\r')=='end' and not '$finish' in prvline:
+                    line = prvline[:-len(prvline.lstrip())] + '$finish;\n' + line
+                    insertfinish = False
                 # remove power pins from reg - optinal, but makes output more readable
                 if not use_power_pins:
                     for p in pp: