SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
The Reduced Media Independent Interface (RMII) specification reduces the pin count between Ethernet PHYs and Ethernet MACs. According to the IEEE 802.3u standard, an MII contains 16 pins for data and control. In devices incorporating multiple MAC or PHY interfaces such as switches, the number of pins adds significant cost with increase in port count. The RMII specification addresses this problem by reducing the pin count to 7 for each port — a 62.5% decrease in pin count.
The RMII module has the following features:
Each nibble is transmitted on the RMII two bits at a time. For a nibble {D3, D2, D1, D0}, the data is transferred as {D1, D0} followed by {D3, D2}.