Media Independent Interface - Reduced Media Independent Interface

Reduced Media Independent Interface

Reduced Media Independent Interface (RMII) is a standard which was developed to reduce the number of signals required to connect a PHY to a MAC. Four things were changed compared to the MII standard to achieve this:

  • The two clocks TXCLK and RXCLK are replaced by a single clock. This clock is an input to the PHY rather than an output, which allows the clock signal to be shared among all PHYs in a multiport device, such as a switch.
  • The clock frequency is doubled from 25 MHz to 50 MHz, while the data paths are narrowed to 2 bits rather than 4 bits.
  • RXDV and CRS signals are multiplexed to one signal.
  • The COL signal is removed.

These changes means that RMII uses about half the number of signals compared to MII. The high pin count of MII is more of a burden on microcontrollers with built-in MAC, FPGA's, multiport switches or repeaters, and PC motherboard chipsets than it is for a separate single port Ethernet MAC which partially explains why the older MII standard was more wasteful of pins.

Read more about this topic:  Media Independent Interface

Famous quotes containing the words reduced, media and/or independent:

    “The physicians say, they are not materialists; but they are:MSpirit is matter reduced to an extreme thinness: O so thin!—But the definition of spiritual should be, that which is its own evidence. What notions do they attach to love! what to religion! One would not willingly pronounce these words in their hearing, and give them the occasion to profane them.”
    —Ralph Waldo Emerson (1803–1882)

    “Few white citizens are acquainted with blacks other than those projected by the media and the so—called educational system, which is nothing more than a system of rewards and punishments based upon one’s ability to pledge loyalty oaths to Anglo culture. The media and the “educational system” are the prime sources of racism in the United States.”
    —Ishmael Reed (b. 1938)

    “Surrealism, n. Pure psychic automatism, by which it is intended to express, whether verbally or in writing, or in any other way, the real process of thought. Thought’s dictation, free from any control by the reason, independent of any aesthetic or moral preoccupation.”
    —André Breton (1896–1966)