SNLS504G October 2015 – June 2026 DP83867CS , DP83867E , DP83867IS
PRODUCTION DATA
When the RGMII interface is operating in the 100Mbps mode, the Ethernet Media Independent Interface (MII) is implemented by reducing the clock rate to 25MHz. For 10Mbps operation, the clock is further reduced to 2.5MHz. In the RGMII 10/100 mode, the MAC generates the transmit clock RGMII TX_CLK and the PHY generates the receive clock RGMII RX_CLK. During the packet receiving operation, the RGMII RX_CLK stretches on either the positive or negative pulse to accommodate the transition from the free-running clock to a data synchronous clock domain. When the speed of the PHY changes, a similar stretching of the positive or negative pulses is allowed. No glitch is allowed on the clock signals during clock speed transitions.
This interface operates at 10Mbps and 100Mbps speeds the same way as at 1000Mbps mode with the exception that the data can duplicate on the falling edge of the appropriate clock.
The MAC holds the RGMII TX_CLK low until the MAC has confirmed that the MAC is operating at the same speed as the PHY.
Figure 7-6 RGMII Connections