The physical layer of Gigabit Ethernet

The physical layer of Gigabit Ethernet is divided into the physical encoded child Layer PCs (physical coding sublayer), the physical Media Connection layer PMA (physical Medium attachment) and the physical media related child layer PMD (physical Medium Dependent) Three Floor

The PCS child layer is responsible for 8B10B encoding, which converts 8-bit parallel data received from Gmii to 10-bit parallel data output. Because 10 bits of data can effectively reduce the DC component, reduce the BER, and use the 8B10B code to facilitate the extraction of the clock in the data and the initial synchronization. You can look at both ends of the PCs as GMII interfaces and TBI interfaces.

The PMA layer further transmits the encoded results of the PCS sub layer to various physical media, mainly responsible for the completion of the string and transformation. The PCS layer transmits 10-bit code in parallel to the PMA layer at a rate of 125M, sending the serial data stream from the PMA layer to 1.25Gbps to actually get the 1Gbps Gigabit Ethernet transfer rate. The two sides of the PMA layer can be regarded as TBI interface and Sgmii interface respectively.

The PMD child layer completes the interface to a variety of physical media and completes the actual physical connection. Because 1000base-x supports a variety of physical media, such as fiber and shielded twisted pair, their physical interfaces are clearly not the same. Some want to do photoelectric conversion, and some to complete the transition from balance to balance. The PMD layer will make provision for these specific connectors.