litex/migen/genlib/resetsync.py

from migen.fhdl.std import *
from migen.fhdl.specials import Special
from migen.fhdl.tools import list_signals

class AsyncResetSynchronizer(Special):
    def __init__(self, cd, async_reset):
        Special.__init__(self)
        self.cd = cd
        self.async_reset = async_reset

    def iter_expressions(self):
        yield self.cd, "clk", SPECIAL_INPUT
        yield self.cd, "rst", SPECIAL_OUTPUT
        yield self, "async_reset", SPECIAL_INPUT

    @staticmethod
    def lower(dr):
        raise NotImplementedError("Attempted to use a reset synchronizer, but platform does not support them")