When you make ports external with the XPS GUI "Ports -> Make External" command, the port names are set to __NOC__ as shown:
PORT mpmc_0_DDR2_DM_pin = __NOC__, DIR = OHow do I resolve this issue?
To fix this problem, perform the following:
A tactical patch is available to address this problem:
http://www.xilinx.com/txpatches/pub/swhelp/ise11_updates/ar33935_nt_patch.zip
http://www.xilinx.com/txpatches/pub/swhelp/ise11_updates/ar33935_lin_patch.zip
http://www.xilinx.com/txpatches/pub/swhelp/ise11_updates/ar33935_lin64_patch.zip
This problem is fixed in 11.5 as well as in 12.1.