create_clock -period "10.000 ns"  -name sys_clk_100mhz        [get_ports {sys_clk}]
create_clock -period "4.000 ns"   -name ref_clk_250mhz        [get_ports {ref_clk}]
create_clock -period "8.000 ns"   -name eth_rx_clk_125mhz     [get_ports {eth_rx_clk}]

derive_pll_clocks
derive_clock_uncertainty