What is the difference between MII and RMII, and how do they relate to products like the DS34T108?
A2. Media-independent interface (MII) and reduced media-independent interface (RMII) are the specifications that are used to communicate between an Ethernet PHY and a media access control (MAC) device. IEEE® 802.3 defines MII as a complete interface with 16 pins that has both data and control signals. RMII reduces the pin count from 16 to 8. However, the tradeoffs of using RMII are that the Tx and Rx clock lines are tied together, and the transmission clocks range from 25MHz to 50MHz. Figure 1 shows the connections between the DS34T108 and a generic Ethernet PHY in MII mode. Note that all 16 pins are required when operating in MII mode. The transmit and receive paths are in separate clock domains. Figure 1. The DS34T108 is connected to an Ethernet PHY in MII mode.
