ERROR:LIT:600 - IOBUFDS symbol "DDR2_SDRAM/DDR2_SDRAM/u_ddr2_top/u_mem_if_top/u_phy_top/u_phy_io/gen_dqs.u_iob_dqs/gen_dqs_iob_ddr2.u_iobuf_dqs" (output signal=DDR2_SDRAM/DDR2_SDRAM/u_ddr2_top/u_mem_if_top/u_phy_top/u_phy_io/gen_d qs.u_iob_dqs/dqs_ibuf) does not have IOSTANDARD specified. Map is unable to generate a default IOSTANDARD for IOBUFDS, one has to be explicitly provided.
what are the IO pins (location, signame) associated with the IOBUFDS IOs?
You might want to open PLANAHEAD app and check for "unassigned" pins.
SIGNATURE: README for newbies is here: http://forums.xilinx.com/t5/New-Users-Forum/README-first-Help-for-new-users/td-p/219369
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