OpenFPGA/libs/libclkarchopenfpga/arch/example.xml

<clock_networks> 
  <clock_network name="example_network" width="8"> 
    <spine name="spine_lvl3" start_x="0" start_y="2" end_x="2" end_y="2"> 
      <switch_point tap="spine_lvl2" x="2" y="2"/> 
    </spine>  
    <spine name="spine_lvl2_upper" start_x="2" start_y="2" end_x="2" end_y="3"> 
      <switch_point tap="rib_lvl1_upper_left" x="2" y="3"/> 
      <switch_point tap="rib_lvl1_upper_right" x="2" y="3"/> 
    </spine> 
    <spine name="spine_lvl2_lower" start_x="2" start_y="2" end_x="2" end_y="1"> 
      <switch_point tap="rib_lvl1_lower_left" x="2" y="1"/> 
      <switch_point tap="rib_lvl1_lower_right" x="2" y="1"/> 
    </spine> 
    <spine name="rib_lvl1_upper_left" start_x="2" start_y="3" end_x="1" end_y="3"/> 
    <spine name="rib_lvl1_upper_right" start_x="2" start_y="3" end_x="3" end_y="3"/> 
    <spine name="rib_lvl1_lower_left" start_x="2" start_y="1" end_x="1" end_y="1"/> 
    <spine name="rib_lvl1_lower_right" start_x="2" start_y="1" end_x="3" end_y="1"/> 
  </clock_network>  
</clock_networks>