When using the LogiCORE XAUI Core in Virtex-4, DCMs are instantiated in the top-level wrapper file to create the appropriate clocks for the XAUI Core and GT11s. How do the new Virtex-4 timing parameters affect these DCMs? Is the DCM_STANDBY macro required?
Refer to (Xilinx Answer 21605) for details on how different Virtex-4 stepping levels affect your design when targeting Virtex-4 devices.
For information on the new Virtex-4 timing parameters, see (Xilinx Answer 21127). Notice that the DCM_STANDBY macro is required to meet the DCM_INPUT_CLOCK_STOP and DCM_RESET requirements. The DCM_STANDBY macro can be manually instantiated or automatically inserted by ISE depending on the stepping level of the device that is being targeted as indicated in (Xilinx Answer 21605).
If it is determined that manual insertion of the macro is required, refer (Xilinx Answer 21127) for more information on how to use the macro.