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AR# 36217

12.1 ERROR: LIT:600 Implementation failed in map: (output signal=ddr2_dqsn[8]) does not have IOSTANDARD specified.


I have not assigned an I/O standard to some pins in my design. The implementation tools do not choose a default I/O standard, but instead print the following error:

ERROR:LIT:600 - IOBUFDS symbol "appc/ddr/ddr/u_mem_if_top_0/u_phy_top_0/u_phy_io_0/genblk16
.gen_dqs[8].gen_phy_dqs_iob.u_iob_dqs/iobuf_dqs" (output signal=ddr2_dqsn[8]) does not have IOSTANDARD specified. Map is unable to generate a default IOSTANDARD for IOBUFDS, one has to be explicitly provided.


Map is unable to assign default IOSTANDARDs for differential I/O because IOBUFDS symbols are expanded differently depending on the IOSTANDARD involved, and this happens upstream of the point where default IOSTANDARDs are assigned. It is necessary for the user to always assign IOSTANDARDs to IOBUFDS symbols.

AR# 36217
Date 11/29/2010
Status Active
Type Known Issues
  • Virtex-5 FXT
  • ISE Design Suite - 12.1