RGMII(Reduced Gigabit Media Independent Interface)
Ethernet MAC和PHY之间数据传递的一种MII（Media Independent Interface）接口，，GMII的精简接口，时钟不变，但在时钟上升和下降沿均收发数据，最高支持1000Mbps。
常用标准
Reduced Gigabit Media Independent Interface (RGMII) 4/1/2002 Version 2.0
Reduced Gigabit Media Independent Interface (RGMII) 12/10/2000 Version 1.3
V2.0相对于V1.3引入了CLK Delay，具体的调测见文档： TI RGMII Interface Timing Budgets
原理图设计
RGMII信号连接如下图（图中PHY的TX和RX按按照MAC侧定义的，即MAC的TX应连接PHY的RX，MAC的RX连接PHY的TX）：
RGMII各信号的定义见下表：
| Table 12: RGMII Signal Definitions | ||
| Signal Name | Source | Description |
| GTXCLK | Switch/MAC | Transmit Clock.This clock is 125 MHz in 1000BASE-T mode,25 MHz in 100BASE- TX mode,and 2.5 MHz in 10BASE-T mode. |
| TXEN (TXEN/TXER) | Switch/MAC | Transmit Control.This signal has a number of functions multiplexed onto it. |
| ·TXEN=Transmit Enable.This information is presented on the rising edge of the transmit clock in RGMIl mode. |
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| ·TXER=Transmit Error.This information is presented on the falling edge of the transmit clock in RGMIl mode. |
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| TXD[3:0] | Switch/MAC | Transmit Data.Data bits TXD[3:0]are presented on the rising edge of the transmit clock in both RGMII.Data bits TXD[7:4]are presented on the falling edge of the transmit clock in RGMIl mode. |
| RXC | PHY | Receive Clock.This clock is 125 MHz in 1000BASE-T mode,25 MHzin 100BASE-TX mode,and 2.5 MHz in 10BASE-T mode. |
| RXDV (RXDV/RXER) | PHY | Receive Control.This signal has a number of functions multiplexed onto it. |
| ·RXDV=Receive Data Valid.This information is presented on the rising edge of the receive clock in RGMIl mode. |
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| ·RXER=Receive Error.This information is presented on the falling edge of the receive clock in RGMIl mode. |
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| RXD[3:0] | PHY | Receive Data.Data bits RXD[3:0]are presented on the rising edge of the receive and data bits RXD[7:4]are presented on the falling edge of the receive clock. |
| MDC | Switch/MAC | Management Data Clock. |
| MDIO | Both | Management Data. |
电平转换：RGMII电平一般有1.8V、2.5V和3.3V三种，MAC和PHY尽量配置成同样的电平，避免使用电平转换芯片。如果电平无法一致，因其时钟频率高，三极管或MOS管的电平转换电路不满足此频率要求，需要用专门的转换芯片。TI提供的电平转换芯片见文档“ Voltage Translation Buying Guide”。