What is the High Speed Serial Communication?
High-speed serial communication is a method of transmitting data bit by bit over a single or multiple lanes at very high speeds. It is widely used in modern computing, networking, and embedded systems due to its efficiency and scalability
- 1 Gbps – 10 Gbps → Used in Gigabit Ethernet (1000BASE-X), PCIe Gen1/2, SATA, USB 3.0
- 10 Gbps – 25 Gbps → Found in 10GBASE-R Ethernet, PCIe Gen3, Fibre Channel
- 25 Gbps – 100 Gbps → Used in PCIe Gen4/5, 100G Ethernet, InfiniBand
- Beyond 100 Gbps → Applied in Terabit optical networks, advanced data centers
Features
- Differential Signaling
- Uses two complementary signals to reduce noise and improve signal integrity.
- Serializer / De-serializer (SerDes)
- Serializer
- Converts parallel data into serial bitstream for trasmission
- Deserializer
- Converts serial stream back into parallel data on receive side.
- Serializer
- Clock and Data Recovery (CDR)
- Instead of transmitting a separate clock signal, the receiver extracts timing information from the data stream.
- Encoding Techniques
- 8B/10B Encoding (used in PCIe, Gigabit Ethernet) ensures DC balance and clock recovery.
- 64B/66B Encoding (used in 10G Ethernet) improve efficiency while maintaining synchronization.
- Gearbox
- Converts data between different widths to match the requirements of the internal parallel processing logic and the serial interface.
- It is essential when the internal data-path width (e.g., 64bit) does not match the encoding or serialization width (e.g., 66-bit for 64b/66b or 10-bit for 8b/10b).
- Signal Integrity and EMI Reduction
- Techniques like pre-emphasis, equalization, and scrambling help maintain signal quality.
- Scrambling randomizes data patterns to reduce electromagnetic interference (EMI).
Common Protocols
| Protocol | Use Case | Encoding Method | Speed Range |
|---|---|---|---|
| PCI Express (PCIe) | GPU, SSDs, accelerators | 8b/10b (Gen1/2), scrambling (Gen3+) | 2.5–64 GT/s per lane |
| SATA/SAS | Storage drives | 8b/10b | 1.5–12 Gbps |
| Ethernet | Networking | 8b/10b, 64b/66b | 1G, 10G, 25G, 100G+ |
| USB 3.x / 4 | General I/O | 8b/10b + scrambling | 5–40 Gbps |
| HDMI / DisplayPort | Video output | TMDS (transition-minimized) | 3–48 Gbps |
| Thunderbolt | Universal data/video | PCIe + DisplayPort + USB | Up to 80 Gbps |
| Aurora | FPGA serial links | Optional (Xilinx proprietary) | Flexible |
Gigabit Transceiver
AMD’s Transceiver (GTY/GYH/GYX) plays a crucial role in enabling high speed serial communication within FPGA systems, facilitating efficient data exchange between external devices.
Key Features of GTY Transceivers
- Supports speed up to 32.75 Gbps for UltraScale+ FPGAs, 30.5 Gbps for UltraScale FPGAs
- Broad Protocol Support: Compatible with PCIe Gen3, Ethernet, Interlaken, SDI, and other high-speed serial protocols.
- Adaptive Equalization
- Clock Recovery & Jitter Reduction
- Encoding and Decoding: 8B/10B, 64B/66B and 64B/67B support, 128B/130B for PCI Express Gen3
- Enhanced 64B/66B and 64B/67B gearbox support.
- Low Power Consumption
- Backplane & Optical Interconnects
- Seamless FPGA Integration
FPGA transceivers support various features required for high-speed serial communication, including clock recovery, adaptive equalization, encoding and decoding, and multi-protocol compatibility. These transceivers support reliable and efficient data transfer in applications such as networking, data centers, and high-performance computing.