Hi,I use ethernet port on terasic DE3 and DE2-115, GMII and RGMII respectively. The clocks are both 125MHz, could anyone tell me any requirement for the timing shift? It seems in RGMII mode I have to shift the clock signal by 90 degree.
not entirely true. if it is a marvel phy, there is a mdio register that causes the phy to perform the needed clock shifts. by default, rgmii requires tx data to be center aligned, and rx data will be edge aligned, necessitating a 90deg shift for the RX data.if you are using a more recent quartus, there is an example sw project for rgmii that sets this bit appropriately. --dalon