xilinx/common/primitives/iob33/modes/no_ibuf.xml

<mode name="NO_IBUF" xmlns:xi="http://www.w3.org/2001/XInclude">
  <xi:include href="../inpad.pb_type.xml"/>
  <interconnect>
    <direct name="I" input="inpad.inpad" output="IOB33_MODES.I">
      <metadata>
        <meta name="fasm_mux">
          inpad.inpad : LVCMOS12_LVCMOS15_LVCMOS18_LVCMOS25_LVCMOS33_LVDS_25_LVTTL_SSTL135_SSTL15_TMDS_33.IN_ONLY,LVCMOS25_LVCMOS33_LVTTL.IN,PULLTYPE.NONE
        </meta>
      </metadata>
    </direct>
  </interconnect>
</mode>