From Silicon To Software

 

New USB 80Gbps Specification Boosts Data Rate, Enables Four Protocols on One Bus

usb specification

By Gervais Fong, Director of Product Marketing, and Morten Christiansen, Senior Technical Marketing Manager, Synopsys Solutions Group

The Universal Serial Bus (USB) connector has a wide range of users—your daughter in high school who needs to plug in her computer at the library and your elderly father-in-law who just got his first tablet, for instance. Because everyone in the connected world uses peripheral connectors to link devices to host computers, other devices, and power supplies, the engineers behind the USB Type-C (USB-C) standard strive to make connecting as consumer friendly as possible.

Device technology is evolving, and that means that peripheral connector technology is evolving, too. The leading standards today in peripheral connector technology include Thunderbolt (developed by Intel and Apple), Lightning (Apple proprietary, gradually being phased out in favor of USB-C), DisplayPort (developed by VESA), and USB (developed by USB Implementers Forum, USB-IF, ). While each of these technology standards is distinct, we will take a deep dive into USB-IF’s USB-C technology, specifically due to its emerging ubiquity. Read on to learn more about why USB-C is growing in popularity and how the latest update, USB 80Gbps, better enables next-generation device connectivity.

USB Standards and Technology – A Look Back

Improved performance is a chief differentiator for each generation of the USB standard. It had humble beginnings back in 1996 at 1.5Mbps and performance levels have kept evolving to 80Gbps today, a 16x increase in the last 14 years!

In addition to advancing performance, the 2015 USB-C update was particularly notable. It streamlined peripheral connectivity by including DisplayPort Alternate Mode into the USB-C standard. From that point forward, instead of needing different cables for each of these two prevalent standards, the same type of connector and cable sufficed to handle high-throughput data, video, audio, and power. The update also introduced the unidirectional cable and connector, so it didn’t matter which way the cable was plugged into the receptacle—both sides of the plug were the right side up. A single cable to connect peripherals was an elegant, clean alternative to reduce that tangle of cables in your junk drawer or under your desk and has helped to spur USB-C popularity.

usb standards

USB’s Rich Set of Capabilities Enable a Burgeoning Ecosystem

Thunderbolt and USB-C coming together in 2019 (this update was previously known as the USB4 standard, and it is now called USB 40Gbps) solidified the emergence of a prolific ecosystem. In a recent survey we conducted, there were over 200 different models of Thunderbolt and USB 40Gbps enabled host computers currently available, and that number is growing. Because of this traction—virtually all desktops and laptops support the USB-C standard—and peripheral devices and docking stations using USB-C have become ubiquitous.

With the new USB 80Gbps standard, a single cable from your laptop or desktop can connect to:

  • Multiple displays, including FHD, QHD, 4K UHD, 5K and 8K
  • A very high-performance mass storage external drive
  • A dedicated board for AI/ML/DL applications processing data at the edge and transferring it back to the host for higher order functions
  • Power supply providing up to 240W
  • Keyboard, mouse, gaming controller, headset, and much more

Because the performance level is so high with USB 80Gbps, you can also connect a number of devices simultaneously, providing a clean, single interface connection to your host system.

usb c port

Unpacking the USB 80Gbps Specification

Here are the key features of the new USB 80Gbps release:

  • Two lanes at 40G per lane—Compared to the previous generation USB 40Gbps, USB 80Gbps uses the same number of lanes with double the bandwidth per lane.
  • PAM 3 encoding—Improved from the previous generation’s Non-Return to Zero (NRZ) encoding.
  • Existing passive cable and connector usage—There are no re-timers or re-drivers needed for short, affordable cables up to 0.8m. Longer active cables will also be available in the near future.
  • Backwards compatibility—USB 80Gbps is compatible with all the previous generations of the USB-C standard. Whether you are connecting the latest devices or a 25-year-old mouse using a legacy version of the specification, USB 80Gbps will work.
  • Support for all legacy USB protocols, plus support for DisplayPort, Thunderbolt, and tunneled PCI Express (PCIe) protocols —The USB 80Gbps specification supports four protocols in one bus. In 2019, the USB 40Gbps standard (previously USB4) supported both USB-C and Thunderbolt, including the ability to encapsulate and tunnel USB-C, PCIe, host-to-host and DisplayPort packets. The latest specification enables twice the number of packets, up to 80Gbps total throughput.
  • Asymmetric mode—USB 80Gbps has data transfer capability up to 160Gbps per second. In the symmetric mode this means the capability is 80G in the transmit (TX) data transfer and 80G capability in the receive (RX) data transfer. In the asymmetric mode, the standard supports up to 120G TX and 40G RX. The asymmetric mode is especially useful for applications where most of the data is being transmitted out of the host computer versus data received, such as display connections. For instance, 80Gbps can be reserved for DisplayPort 1.4a or the new DisplayPort 2.0/2.1 standard while still leaving 40Gbps TX and RX for tunneled USB-C, PCIe, and Host-to-Host traffic.
  • New Gen-T, otherwise known as direct connect mode—Engineers have the option to design future USB-C peripherals that connect at lightning-fast rates to 120Gbps TX and 40Gbps RX per second, opening up a new realm of innovation possibilities.

USB-C: Simple and Elegant for the Consumer, Backed by Complex Engineering

Oftentimes the most elegant solutions are achieved only after working through great complexity. The USB-C protocol is no exception. Even so, as USB-C rates increase and the complexity of devices increase, your design effort will, no doubt, also increase: You have mixed-signal, digital, software, and system-level considerations to juggle. There is simply more to think about these days. This is even more true, if your end goal is a consumer-oriented solution that must be intuitive and easy-to-use, working right the first time and in the future.

As your design challenges get more complex, Synopsys can help you simplify your USB design effort. Our comprehensive portfolio of Synopsys USB IP solutions includes Controller and PHY IP, verification IP, IP subsystems, and prototyping kits. With over 20 years successfully providing USB digital and mixed-signal solutions and over $1 billion in USB IP sales, we help designers implement their next-generation USB-enabled chip designs with less risk.

If you’d like to explore USB 80Gbps for your next SoC, download our white paper, User Expectations Drive Design Complexity, or contact us for help getting started.

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