Project maintainers


Name: smii
Created: Mar 19, 2009
Updated: Mar 19, 2009
SVN Updated: Apr 28, 2009
SVN: Browse
Latest version: download (might take a bit to start...)
Statistics: View
Bugs: 0 reported / 0 solved
Star6you like it: star it!

Other project properties

Category:Communication controller
Development status:Beta
Additional info:Specification done
WishBone compliant: No
WishBone version: n/a


The Serial Media Independent Interface, SMMI, is a low pin count version of the MII normally used between ethernet MAC and PHY.

The Serial Media Independent Interface (SMII) is designed to satisfy the following requirements:
  • Convey complete MII information between a 10/100 PHY and MAC with two pins per port
  • allow multi port MAC/PHY communications with one system clock
  • Operate in both half and full duplex
  • per packet switching between 10 Mbit and 100 Mbit data rates
  • allow direct MAC to MAC communication

SMII is composed of two signals per port, global synchronization signal, and a global 125 MHz reference clock.

All signals are synchronous to the clock.

Name From To Use
RX PHY MAC Receive data and control
TX MAC PHY Transmit data and control
SYNC MAC PHY Synchronization
CLOCK System MAC & PHY Synchronization

Block diagram

Typical application

The picture above shows a typical application with an external quad Ethernet PHY that connects to four Ethernet MACs inside a FPGA.

This example uses a total of 10 signal to implement this function.

Resource usage

Target smii_sync smii_rxtx
ACTEL ProASIC3 10 slices 117 slices
ALTERA Cyclone III Combinatorial functions 2
DFFs 10
Combinatorial functions 52
DFFs 36


  • 2009 March 13
    initial design commited to repository.
    Limited testing performed on OpenRISC hardware platform