Traceback (most recent call last):
  File "pcrtc.py", line 260, in <module>
    sim.run()
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 820, in run
    while self.step():
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 811, in step
    self._run_process(process)
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 774, in _run_process
    process.throw(e)
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 465, in clk_process
    yield clk.eq(1)
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 750, in _run_process
    self._commit_sync_signals(domains)
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 690, in _commit_sync_signals
    self._run_process(process)
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 774, in _run_process
    process.throw(e)
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 433, in sync_process
    result = yield cmd
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/back/pysim.py", line 754, in _run_process
    cmd = process.send(self._state.curr[self._signal_slots[cmd]])
  File "/usr/local/lib/python3.6/dist-packages/nmigen-72cf4ca-py3.6.egg/nmigen/hdl/ast.py", line 1205, in __getitem__
    return self._storage[key]
KeyError: <nmigen.hdl.ast.SignalKey (sig d_hblank)>