diff --git a/milkymist/clkfx/__init__.py b/milkymist/clkfx/__init__.py
new file mode 100644
index 000000000..9eb5600ae
--- /dev/null
+++ b/milkymist/clkfx/__init__.py
@@ -0,0 +1,38 @@
+from fractions import Fraction
+
+from migen.fhdl.structure import *
+
+class Inst:
+	def __init__(self, infreq, outfreq):
+		declare_signal(self, "clkin")
+		declare_signal(self, "clkout")
+		
+		ratio = Fraction(outfreq)/Fraction(infreq)
+		appr = ratio.limit_denominator(32)
+		m = appr.numerator
+		if m < 2 or m > 32:
+			raise OverflowError
+		d = appr.denominator
+		
+		in_period = float(Fraction(1000000000)/Fraction(infreq))
+		
+		self._inst = Instance("DCM_SP",
+			[("CLKFX", self.clkout)],
+			[("CLKIN", self.clkin),
+			("PSEN", BV(1)),
+			("RST", BV(1))],
+			[("CLKDV_DIVIDE", 2.0),
+			("CLKFX_DIVIDE", d),
+			("CLKFX_MULTIPLY", m),
+			("CLKIN_DIVIDE_BY_2", "FALSE"),
+			("CLKIN_PERIOD", in_period),
+			("CLKOUT_PHASE_SHIFT", "NONE"),
+			("CLK_FEEDBACK", "NONE"),
+			("DESKEW_ADJUST", "SYSTEM_SYNCHRONOUS"),
+			("DUTY_CYCLE_CORRECTION", "TRUE"),
+			("PHASE_SHIFT", 0),
+			("STARTUP_WAIT", "TRUE")]
+		)
+
+	def get_fragment(self):
+		return Fragment([self._inst.ins["PSEN"].eq(0), self._inst.ins["RST"].eq(0)], instances=[self._inst])