gigabit media independent interface (GbE) (GMII)
The GigabitMedia Independent Interface (GMII) forms the interface between the Medium Access Control ( MAC) and the Physical Layer( PHY) in the layer model ofGigabit Ethernet.
The GMII interface is a media-independent interface with 24 pins that can be used with different transmission media. Data rates up to 1 Gbit/s are defined. The GMII interface uses an 8-bit interface clocked at 125 MHz.Data is transmitted over eight data lines in each direction. In addition, the GMII interface has six status lines for the transmission of error signals and signals fordata integrity. There is an R version, which stands for Reduced, RGMII, which uses only four data lines in each direction and has only 12 pins.
The GMII interface is backward compatible with the Media Independent Interface( MII) specifications. Therefore, it can also work with the data rates of classic Ethernet of 10 Mbit/s and Fast Ethernet of 100 Mbit/s. The transmitted data format on the GMII interface corresponds to the Ethernet frame.