The ISE software can generate the following error message for a Spartan-6 MIG MCB design:
"ERROR:PhysDesignRules:2268 - Invalid configuration (incorrect pin connections and/or modes) on block:<hierarchy/memcx_infrastructure_inst/BUFPLL_MCB_INST>:<BUFPLL_MCB_BUFPLL_MCB>. In order to ensure proper reset behavior, the GCLK, LOCKED and LOCK pins all need to be connected appropriately. Please see AR#35976 for specific details."
This error message can indicate that an older version MIG design witha previousversion of the BUFPLL_MCB instantiation is being compiled in ISE tools version 12.2 or higher.
This error message can also indicate that the sys_rst signal to the Spartan-6 MIG or MPMC design has been incorrectly (permanently) asserted in the user's design.