Some of the common errors that are encountered and the solution for these type of errors:
"ERROR:Pack:499 - The I/O component "DATA_IN_FROM_PINS_N<0>" has an illegal IOSTANDARD value. The target architecture does not support IOSTANDARD value DIFF_HSTL_IV. Please correct the IOSTANDARD property value."
This error means that the particular IOSTANDARD is not supported in the device that is used for the design. The best way to check for IOSTANDARD support would be in the user guide for the architecture:
Virtex-4 FPGA: http://www.xilinx.com/support/documentation/user_guides/ug070.pdf
Spartan-3 FPGA: http://www.xilinx.com/support/documentation/user_guides/ug331.pdf
Virtex-5 FPGA: http://www.xilinx.com/support/documentation/user_guides/ug190.pdf
Virtex-6 FPGA: http://www.xilinx.com/support/documentation/user_guides/ug361.pdf
Spartan-6 FPGA: http://www.xilinx.com/support/documentation/user_guides/ug381.pdf
In this particular case, the IOSTANDARD DIFF_HSTL_IV is not supported in the Spartan-6 architecture.
"ERROR:Pack:2409 - The I/O component "CLK_n" has an illegal IOSTANDARD value.The IBUF component is configured to use single-ended signaling and can not use differential IOSTANDARD value LVPECL_33. Please correct the IOSTANDARDproperty value or the I/O connectivity."
These pack errors can occur if you haveinstantiated a wrong buffer type for the IOSTANDARD being used or if you do not have a buffer instantiated at all.
Forexample, if you are using LVDS_25 (differential IOSTANDARD) and you have a IBUF instantiated, the above error occurs. You have to make sure that you instantiate a differential buffer like IBUFDS. Please refer to the libraries guide for various buffer types.
"ERROR:Pack:1107 - Pack was unable to combine the symbols listed below into a single DIFFSTB component because the site type selected is not compatible. The root cause of failure is that the IOSTANDARD=LVDS_25 property is only supported in the TOP and BOTTOM IO banks."
The component type is determined by the types of logic and the properties and configuration of the logic it contains. In this case an I/O component of type DIFFSTB was chosen because the I/O contains symbols and/or properties consistent with differential slave usage and a IOSTANDARD=LVDS_25 property. 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.
These types of errors can occur due to hardware limitation for a particular architecture. In the case above, the target architecture was Spartan-3 and the differential IOSTANDARD outputs are only supported on BANK 0 and BANK 2 (top and bottom banks).
IOSTANDARD restrictions are documented in the architecture specific user guide.