Hi guys，I'm using the tse mac core(ver8.0) with CycloneIII and a vitesse gbit speed phy(which is vsc8244), now I'm encountering a problem with the mac core using. I set the mac core in loopback mode and I can receive data in user application, then i set the phy in near-end loopback mode and the mac core in normal mode, the data cannot be received in mac core. The signal ff_rx_dsav and ff_rx_dval never asserted, but the phy dose sent back the data to fpga(i checked the rgmii receice signals with a scope and signaltap). I was wondering if there's some timing constraint problems with my design. could anyone provide some suggestions? thanks. BTW, the tse mac core works in 1000Mbps speed rgmii mode and my design chooses the "MegaWizard Plug-in Manager Flow".