self = <nmigen.back.pysim.Simulator object at 0x7fb1836445f8>, run_passive = False

    def step(self, run_passive=False):
        # Are there any delta cycles we should run?
        if self._state.curr_dirty.any():
            # We might run some delta cycles, and we have simulator processes waiting on
            # a deadline. Take care to not exceed the closest deadline.
            if self._wait_deadline and \
                    (self._timestamp + self._delta) >= min(self._wait_deadline.values()):
                # Oops, we blew the deadline. We *could* run the processes now, but this is
                # virtually certainly a logic loop and a design bug, so bail out instead.d
>               raise DeadlineError("Delta cycles exceeded process deadline; combinatorial loop?")
E               nmigen.back.pysim.DeadlineError: Delta cycles exceeded process deadline; combinatorial loop?

nmigen/back/pysim.py:755: DeadlineError