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Altera_Forum's avatar
Altera_Forum
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16 years ago

Gigabit Ethernet, Cyclone III and RGMII

I want to interface a gigabit phy to a cycloneIII part using the RGMII as seems to be the case with the 120 Dev kit but upon looking under Switching Characteristics I see that C7 can do 237mhz out and C8 is only good for 225mhz. Toggle Rates seem to be defined as the number of 0->1 or 1->0 transitions per second which would seem to imply 1000mhz/4 pins in RGMII running at 250mhz. I guess the gist of the question is: in the switching characteristics is the toggle rate = (0->1 + 1->0) / sec or either (0->1)/sec or (1->0)/sec?

Probably even shorter question: will the EP3C25E144C8 drive a gigabit Phy using RGMII or is it necessary to use GMII?

Thanks,

Phil

1 Reply

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    The RGMII interface is actually a DDR at 125 MHz. Altera's example design uses a C8, it compiles fine and passes the timing analysis, so there isn't any problem making it run.