mibuild/lattice: add LatticeAsyncResetSynchronizer

mibuild/lattice/common.py

@@ -1,6 +1,21 @@
 from migen.fhdl.std import *
 from migen.genlib.io import *
 
+class LatticeAsyncResetSynchronizerImpl(Module):
+	def __init__(self, cd, async_reset):
+		rst1 = Signal()
+		self.specials += [
+			Instance("FD1S3BX", i_D=0, i_PD=async_reset,
+				i_CK=cd.clk, o_Q=rst1),
+			Instance("FD1S3BX", i_D=rst1, i_PD=async_reset,
+				i_CK=cd.clk, o_Q=cd.rst)
+		]
+
+class LatticeAsyncResetSynchronizer:
+	@staticmethod
+	def lower(dr):
+		return LatticeAsyncResetSynchronizerImpl(dr.cd, dr.async_reset)
+
 class LatticeDDROutputImpl(Module):
 	def __init__(self, i1, i2, o, clk):
 		self.specials += Instance("ODDRA",
@@ -14,5 +29,6 @@ class LatticeDDROutput:
 		return LatticeDDROutputImpl(dr.i1, dr.i2, dr.o, dr.clk)
 
 lattice_special_overrides = {
+	AsyncResetSynchronizer:	LatticeAsyncResetSynchronizer,
 	DDROutput:	LatticeDDROutput
 }