def METHOD_NAME(self, fragment):
    Xilinx7SeriesPlatform.METHOD_NAME(self, fragment)
    self.add_period_constraint(self.lookup_request("clk100",             loose=True), 1e9/100e6)
    self.add_period_constraint(self.lookup_request("eth_clocks:ref_clk", loose=True), 1e9/50e6)