AR# 39138 LogiCORE IP Tri-Mode Ethernet MAC v4.4rev2 and earlier - LogiCORE IP Tri-Mode Ethernet MAC v4.4rev2 and earlier - 11 byte IFG transmitted when core generated for Full Duplex only
When the Tri-Mode Ethernet MAC Core is generated either for MII, GMII, or Tri-speed operation for full duplex only, in the example design simulation the default minimum transmitted IFG is 11 bytes instead of the required 12 bytes per the 802.3 IEEE specification.
Solution
This issue isnot experienced if the core is generated for both full and half duplex support. To work around this problem, enable the IFG Adjust and set tx_ifg_adjust to 12.