The current COREGen constraints for the example design for both the Gigabit Ethernet MAC and the Tri-Mode Ethernet MAC create two separate period constraints from the time groups host and mdio_logic. But they do not constrain the paths going from host to mdio_logic or going from mdio_logic to host.
These paths can be constrained with the additional constraints:
TIMESPEC "TS_mdio3" = FROM "mdio_logic" TO "host" "TS_host_clk";
TIMESPEC "TS_mdio4" = FROM "host" TO "mdio_logic" "TS_host_clk";
This will be fixed in Gigabit Ethernet MAC v8.1 Core and Tri-Mode Ethernet MAC v3.2 scheduled to be released in 8.2i IP Update 2 due out in Fall 2006.