Xilinx的FPGA高速串并转换模块GTP在调用编译时出现：

ERROR:Pack:1107 - Unable to combine the following symbols into a single IOB
   component:
    PAD symbol "GTP_SERDES_IF_inst/SYS_CLK_N" (Pad Signal = SYS_CLK_N)
    SlaveBuffer symbol
   "GTP_SERDES_IF_inst/tile0_gtp0_refclk_ibufds_i/SLAVEBUF.DIFFIN" (Output
   Signal = GTP_SERDES_IF_inst/tile0_gtp0_refclk_ibufds_i/SLAVEBUF.DIFFIN)
   An IO component of type IOB was chosen because the IO contains symbols and/or
   properties consistent with input, output, or bi-directional usage and
   contains no other symbols or properties that require a more specific IO
   component type.
   Each of the following constraints specifies an illegal physical site for a
   component of type IOB:
    Symbol "GTP_SERDES_IF_inst/SYS_CLK_N" (LOC=B12 [Physical Site Type = IPAD])
   The component type is determined by the types of logic and the properties and
   configuration of the logic it contains. Please double check that the types of
   logic elements and all of their relevant properties and configuration options
   are compatible with the physical site type of the constraint.
  
ERROR:Pack:1107 - Unable to combine the following symbols into a single IOB
   component:
    PAD symbol "GTP_SERDES_IF_inst/SYS_CLK_P" (Pad Signal = SYS_CLK_P)
    DIFFAMP symbol "GTP_SERDES_IF_inst/tile0_gtp0_refclk_ibufds_i/IBUFDS"
   (Output Signal = GTP_SERDES_IF_inst/sys_clk)
   An IO component of type IOB was chosen because the IO contains symbols and/or
   properties consistent with input, output, or bi-directional usage and
   contains no other symbols or properties that require a more specific IO
   component type.
   Each of the following constraints specifies an illegal physical site for a
   component of type IOB:
    Symbol "GTP_SERDES_IF_inst/SYS_CLK_P" (LOC=A12 [Physical Site Type = IPAD])
   The component type is determined by the types of logic and the properties and
   configuration of the logic it contains. Please double check that the types of
   logic elements and all of their relevant properties and configuration options
   are compatible with the physical site type of the constraint.
  
  
  
  
ERROR:Pack:1107 - Pack was unable to combine the symbols listed below into a
   single IOB component because the site type selected is not compatible.

   Further explanation:
   The component type is determined by the types of logic and the properties and
   configuration of the logic it contains. In this case an IO component of type
   IOB was chosen because the IO contains symbols and/or properties consistent
   with input, output, or bi-directional usage and contains no other symbols or
   properties that require a more specific IO component type. Please double
   check that the types of logic elements and all of their relevant properties
   and configuration options are compatible with the physical site type of the
   constraint.

   Summary:
   Symbols involved:
    PAD symbol "TILE0_GTP0_REFCLK_PAD_N_IN" (Pad Signal =
   TILE0_GTP0_REFCLK_PAD_N_IN)
    SlaveBuffer symbol "tile0_gtp0_refclk_ibufds_i/SLAVEBUF.DIFFIN" (Output
   Signal = tile0_gtp0_refclk_ibufds_i/SLAVEBUF.DIFFIN)
   Component type involved: IOB
   Site Location involved: B12
   Site Type involved: IPAD

ERROR:Pack:1107 - Pack was unable to combine the symbols listed below into a
   single IOB component because the site type selected is not compatible.

   Further explanation:
   The component type is determined by the types of logic and the properties and
   configuration of the logic it contains. In this case an IO component of type
   IOB was chosen because the IO contains symbols and/or properties consistent
   with input, output, or bi-directional usage and contains no other symbols or
   properties that require a more specific IO component type. Please double
   check that the types of logic elements and all of their relevant properties
   and configuration options are compatible with the physical site type of the
   constraint.

   Summary:
   Symbols involved:
    PAD symbol "TILE0_GTP0_REFCLK_PAD_P_IN" (Pad Signal =
   TILE0_GTP0_REFCLK_PAD_P_IN)
    DIFFAMP symbol "tile0_gtp0_refclk_ibufds_i/IBUFDS" (Output Signal =
   tile0_gtp0_refclk_i)
   Component type involved: IOB
   Site Location involved: A12
   Site Type involved: IPAD
字面意思是FPGA GTP专用时钟I/O无法连接到GTO模块。

出现这个错误的原因是在Synthesize - XST的处理属性中的keep_hierarchy设置成YES,需要设置成NO。