If you target Stratix V devices with a IP core without leveling, the design fails.
Device Family: Stratix® V
Type: Answers, Errata
Area: EMIF, Intellectual Property
To work around this issue, disable the DM pins.The MegaWizard interface does not support design without leveling targeting Stratix V devices (the option is disabled), but you can generate a Stratix V design with leveling.