常见以太网接口介绍_1

一.PHY 包含的各个子层：

PCS:  Encoding and decoding

PMA:  Serializer and Desirializer

PMD: Physical Medium Dependent

Firgure 1: OSI模型里示意图：

Firgure 2: 实际互连示意图：

二.以太网上常见的MAC与PHY之间的接口(按照速度区分)

1. 100M

  MII: Medium Independent Interface (IEEE 802.3 CL22 )

• A digital interface that provides a 4-bit wide datapath between a 10/100 Mbit/s PHY and a MAC sub-layer.
• TXC, TXD[3:0], TXEN, TXER
• RXC, RXD[3:0], RXDV, RXER

  RMII: Reduced Medium Independent Interface

• 对比MII，是信号线数量减半
• 主要支持厂家有BRCM/AMD/TI等

Figure 3：RMII连接示意图：

  SMII: Serial MII

• 串行化的MII
• 信号主要有：REFCLK, STXD, SRXD, SSYNC, TX_EN, RX_DV
• 主要支持厂家有 Cisco

Figure 4：SMII连接示意图：

S3MII:Source Synchronous SMII

• REFCLK, SSMII_RXC, SSMII_RSYNC, RXD, SSMII_TXC, SSYNC, TXD
• 主要支持厂家 Cisco

Figure 5：S3MII连接示意图：

2. 1000M

   2.1>.1GE 并行接口

       GMII:  Gigabit Media Independent Interface, IEEE 802.3 CL35

• A digital interface that provides an 8-bit wide datapath between a 1000 Mbit/s PHY and a MAC sublayer. It also supports the 4-bit wide MII interface as defined in the IEEE 802.3z specification.
• GTXCLK, TXD[7:0], TXEN, TXER
• RXC, RXD[7:0], RXDV, RXER, COL CRS

Figure 6: GMII 连接示意图：

RGMII: Reduced GMII,

-对比GMII，主要是数据线数量减半；

-主要支持厂家有BRCM/HP/MAVL

  2.2>. 1GE 串行接口

      SGMII: Serial MII，1.25G baud rate, Cisco

• A digital interface that provides a 1.25 Gbps serial dual-data-rate datapath between a 1000 Mbit/s PHY and a MAC sublayer.
• SGIN+-/SGOUT+-
• 8b/10b coding

Figure 7： SGMII 连接示意图：

QSGMII: Quad SGMII，5G baud rate，Cisco

• Quad Serial Gigabit Media Independent Interface: A digital interface that provides a 5.0 Gbps serial datapath between four 1000 Mbit/s PHY ports and a MAC sublayer
• QSGMII_RDp/n, QSGMII_TDp/n
• 8b/10b coding

USGMII: Universal SGMII,1.25G/5G/10G baud rate,Cisco

• An extension of current SGMII and QSGMII. USGMII provides flexibility to add new features while maintaining backward compatibility.
• USGMII_RDp/n, USGMII_TDp/n
• 8b/10b coding
• 最多可以支持8个1GE 口
• PCH: Packet Control Header. 这个是最大特点。

PCH provides optional features such as PTP Time Stamp and capability to add features in the future via re-use of Extension Field described below. PHY communicates with a port MAC (ASIC) through PCH. PCH is 8 bytes and it replaces the preamble of the frame.

 1000base-X:  Serdes ,8b/10b codng ,IEEE 802.3 CL36/37

 1000base-KX:  1G背板的应用, 8b/10b coding, IEEE 802.3 CL70

2.3>.扩展—BRCM supports USXGMII:

      USXGMII:  Universal serial XGMII，它是基于一对serdes的一个端口；

      -10.3125G baud rate, 64b/66b coding;

     Figure 9:USXGMII工作在10G和5G时候的区别：

2.4>.比较：

      -  USGMII vs SGMII/QSGMII

       USGMII可以最多支持8个1GE口，通过一对10G serdes，对于高密度的应用更合适；

       USGMII可以过PCH（PacketControlHeader）传递MAC和PHY之间的control/status信息，这对PTP上timestamp的应用提供了便利；

• USGMII vs USXGMII

       USGMII是出8个1GE口，

       USXGMII是出一个口，此口可以是10M/100M/1000M/5G/10G等

3. 10G

      XAUI----10 Gigibit Attachment Unit Interface, IEEE 802.3 CL47 10GBASE-LX4 (CL53),10GBASE-KX4 (CL71), 10GBASE-CX4 (CL54)

• 125Gbps, 8b/10b encoding
• XG_RX[3:0]_p/n, XG_TX[3:0]_p/n
• 4对差分线出1一个10G口；

     DXAUI--- Dual XAUI 4x6.25Gbps, 8b/10b encoding

• XG_RX[3:0]_p/n, XG_TX[3:0]_p/n
• 4对差分线出一个20G口；

    RAXUI--- Reduced XAUI 2x6.25Gbps, 8b/10b encoding

• XG_RX[1:0]_p/n, XG_TX[1:0]_p/n
• 两对差分线出一个10G口；

     XFI:  10 Gigibit Attachment Unit Interface, INF-8077 

• The XFI 用来做10G速率下 chip-to-chip 互联，最初是被XFP multi-source agreement定义.
• 10.3125Gbps, 64b/66b encoding
• 一对差分线出10G口；

    10GBASE-KR: 背板侧应用，IEEE 802.3，CL72

• 主要特点是CL73 AN，CL72 training，CL74 FEC；
• 速率10.3125G，64b/66b编码；
• 一对差分线出一个10G口；

The end.