Media Independent Interface - Reduced Gigabit Media Independent Interface

Reduced Gigabit Media Independent Interface

Reduced Gigabit Media Independent Interface (RGMII) specifies a particular interface between an Ethernet MAC and PHY.

RGMII uses half the number of data pins as used in the GMII interface. This reduction is achieved by clocking data on both the rising and falling edges of the clock in 1000 Mbit/s operation, and by eliminating non-essential signals (carrier-sense and collision-indication). Thus RGMII consists only of: RX_CTL, RXC, RXD, TX_CTL, TXC, TXD (12 pins, as opposed to GMII's 24). Ie FrameStart-BitClock-Data.

Unlike GMII, the transmit clock signal is always provided by the MAC on the TXC line, rather than being provided by the PHY for 10/100 Mbit/s operation and by the MAC at 1000 Mbit/s.

RGMII supports Ethernet speeds of:

Bits/Clockcycle
10 2.5 4
100 25 4
1000 125 8

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