Virtex-4 Embedded Tri-mode Ethernet MAC Wrapper - Implementation of MII interface might fail in MAP due to I/O banking rules

Description

When a design with MII interface is implemented, intermittent failures occur in MAP with the following error: 

"ERROR:Place:864 - Incompatible IOB's are locked to the same bank 2 Conflicting IO Standards are: 
IO Standard 1: Name = LVCMOS25, VRR, VCCO = 2.50, TERM = NONE 
List of locked IOB's: HOSTCLK

IO Standard 2: Name = LVTTL, VREF = NR, VCCO = 3.30, TERM = NONE 
List of locked IOB's: MII_TX_CLK_1 

These IO Standards are incompatible due to VCCO mismatch."

Solution

To avoid this error, add the following constraints in the UCF:  

INST "MII_TX_CLK_1" LOC = "Bank4";  
INST "MII_TX_CLK_0" LOC = "Bank4";  
INST "MII_RX_CLK_1" LOC = "Bank4";  
INST "MII_RX_CLK_0" LOC = "Bank4";