RGMII-dat
🌐 What is RGMII?
RGMII stands for Reduced Gigabit Media Independent Interface.
It's a type of electrical interface used to connect a MAC (Media Access Controller) to a PHY (Physical Layer Transceiver) in Ethernet devices.
📦 What is it used for?
- Used in Gigabit Ethernet (1000 Mbps) hardware
- Common in routers, switches, SoCs, FPGAs, and other networking devices
🧠 Why "Reduced"?
RGMII reduces the number of data lines compared to GMII:
| Interface | Data Lines | Speed |
|---|---|---|
| GMII | 24 | Up to 1 Gbps |
| RGMII | 12 | Up to 1 Gbps |
🔧 RGMII uses double data rate (DDR) — it transfers data on both rising and falling edges of the clock signal, so it needs fewer wires.
⚙️ Key Features
- ✅ Supports 10/100/1000 Mbps Ethernet
- ✅ Uses DDR clocking to reduce pin count
- ✅ Total of 12 signals:
- 4 TX data
- 4 RX data
- TX control
- RX control
- TX clock
- RX clock
🛠️ Typical RGMII Pinout
| Signal | Direction | Description |
|---|---|---|
| TXD[3:0] | MAC → PHY | Transmit data |
| RXD[3:0] | PHY → MAC | Receive data |
| TX_CTL | MAC → PHY | Transmit control |
| RX_CTL | PHY → MAC | Receive control |
| TXC | MAC → PHY | Transmit clock |
| RXC | PHY → MAC | Receive clock |
🔌 Summary
- RGMII = Compact, fast interface for Gigabit Ethernet
- Used between Ethernet MAC and PHY
- Saves pins compared to GMII
- Supports up to 1 Gbps using DDR signaling