If more than two GTX transceivers are instantiated in the IBERT design, and sweep tests are performed, the DFETAP values can only be changed for the first two GTX. This issue only affects the Virtex-5 GTX IBERT design.
To work around this issue, only generate a Virtex-5 GTX IBERT design targetingtwo GTX_DUAL transceivers.If more thantwo transceivers are needed, multiple IBERTdesigns (withtwo GTX DUALs instantiated each) can be generated to perform the sweep tests for all channels that are needed.