GMII全称千兆介质无关接口，应用于互联网，英文全称Gigabit Media Independent。

GMII=Gigabit Media Independent Interface(千兆介质无关接口)

GMII defines the logical and electrical characteristics for the Reconciliation Sublayer (RS) and Gigabit Media Independent Interface (GMII) between CSMA/CD media access controllers and various PHYs. Figure 1 shows the relationship of the Reconciliation sublayer and GMII to the ISO/IEC OSI reference model.

The purpose of this interface is to provide a simple, inexpensive, and easy-to-implement interconnection between Media Access Control (MAC) sublayer and PHYs, and between PHYs and Station Management (STA) entities。

GMII characteristics:

1.It is capable of supporting 1000 Mb/s operation.

2.Data and delimiters are synchronous to clock references.

3.It provides independent eight-bit-wide transmit and receive data paths.

4.It provides a simple management interface.

5.It uses signal levels, compatible with common CMOS digital ASIC processes and some bipolar processes.

6.It provides for full duplex operation.

Application and Rate of operation ：

This clause applies to the interface between the MAC and PHYs, and between PHYs and Station Management entities. The GMII supports only 1000 Mb/s operation and is defined within this clause. Operation at 10 Mb/s and 100 Mb/s is supported by the MII. PHYs that provide a GMII shall support 1000 Mb/s operation, and may support additional rates using other interfaces (e.g., MII).