What is USB 3.0? What can you do with it?
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The USB 3.0 Promotion Team was formed at the 2007 Intel Information Technology Summit. Six member companies (HP, Intel, Microsoft, NEC, ST-NXP Wireless, Texas Instruments) drafted the original specification and formed an organization of 200 industry experts with other participating companies to ensure that when the specification was released Can get a wide range of support. This specification was completed in October 2008, and any company wishing to adopt it will be able to obtain the specification in mid-November 2008.
Figure 1 SuperSpeed ​​USB 3.0 logo
The most obvious difference between SuperSpeed ​​USB and the old version is that the speed is increased by more than 10 times: from 480Mb/s to 5Gb/s. Although USB 2.0 is high speed, even USB full speed (12Mb/s) and low speed (1.5Mb/s) can satisfy many applications, USB connection may still be a big bottleneck in other applications.
In addition, SuperSpeed ​​USB will continue to inspire the industry's innovative ideas to develop new applications and devices to take advantage of better performance. The data transmission rate of 5Gb/s should be able to provide room for development in the next five years or more.
The increased transmission speed of new cable structures presents challenges for existing USB 2.0 cables. SuperSpeed ​​USB requires a shielded differential pair (SDP) cable to ensure signal integrity and minimize electromagnetic interference. At the same time, the maximum cable length has been reduced from 5m for USB 2.0 to 3m for SuperSpeed ​​USB.
The physical layer's electronic signaling scheme has also evolved from a simple two-wire system to a dual-simplex data path. This is achieved through a completely separate connection and is no longer a two-wire interface in existing USB 2.0. The purpose of this is to be able to achieve a 5Gb/s transmission rate on a 3m cable. In addition, although changes are required to meet the electronic signaling scheme, the host does not have to provide a new form factor plug or socket; if possible, no changes are required on the peripheral.
Figure 2 Super high-speed USB cable cross-section shows the difference with 2.0
Ultra-High Speed ​​USB Signaling Scheme To minimize risk, the promotion team determined that the new signaling scheme should be similar to PCI-Express. This connection retains the sideband function without the need for additional wires and provides the receiver with the ability to detect connections/disconnections.
The signaling schemes for SuperSpeed ​​USB and PCI-Express are quite different. SuperSpeed ​​USB does not use a common clock architecture. It requires a spread spectrum on both sidebands and requires equalization at the receiving end. The processing of time jitter also takes a different approach. At the same time, this solution does not provide sideband pins for connection/disconnection detection, link reset, power management control or wake-up.
Another key change is to increase bus power efficiency. This is very beneficial to extend the battery life of portable devices, which is suitable for both the host and peripheral devices. This specification defines excellent power supply characteristics, especially for idle links. Both the upstream and downstream ports enable the link to enter a low power state. Local power management controls use multiple link power states to further improve power efficiency. Another method of energy saving eliminates the need for rotational testing of all equipment.
The key to the SuperSpeed ​​USB standard is to provide upward compatibility with USB 2.0 as much as possible. As mentioned earlier, the signaling scheme of SuperSpeed ​​USB is implemented by different wires, which is different from USB 2.0.
This poses a significant challenge to the cable and connector working group: they need to add 5 wires to the socket and plug, and also need to ensure that the existing USB 2.0 plug can be plugged into the SuperSpeed ​​USB socket, SuperSpeed ​​USB 3.0 The plug can be plugged into a USB 2.0 socket and the link works in all cases.
Solution: Add 5 wires to the insertion face of the existing plug and socket. This provides the same mechanical interface as USB 2.0, providing complete backward compatibility (see Figures 3 through 5).
Figure 3 SuperSpeed ​​USB Standard Type A Socket and Plug
Figure 4 SuperSpeed ​​USB Standard Type B Plug and Socket
Figure 5 SuperSpeed ​​USB Micro-B type socket and plug
The existing Micro-B type socket (see Figure 5) does not provide space for adding five wires, so large changes are required, with a 2.0 and 3.0 interface. This connector should only be used for small portable devices. To avoid incorrect insertion, the SuperSpeed ​​USB Micro-A and AB connectors differ from the Micro-B connectors in terms of bite plugs and profiles, but are otherwise identical.
As with mechanical backward compatibility, the goal is to retain a large amount of device-driven infrastructure. The same data transfer types, interrupts, block and isochronous storage devices are preserved. Finally, this standard preserves the ease of use of existing USB.
The application and benefit of higher transfer rates reduces latency when transferring data from a computer to a portable consumer device. End users are looking for an excellent fast sync experience when using devices with a lot of content, such as music players, video players, digital cameras, and camcorders.
The dramatic increase in file size has driven an increase in storage capacity. 10 years ago, the size of a normal digital camera was 1M. After 5 years, this number will become around 5M. Today, many cameras produce 14M photos, while camera phones are 8M. The driving force behind this growth is the increase in storage capacity and the need to perfectly store all the photos throughout the week. The same is true for camcorders. They offer camera functions (the resolution is usually lower than the average stand-alone camera, but the resolution is also growing), as well as high-quality video including HD MPEG2. Both types of recording need to be transmitted frequently, that is, these files need to be frequently uploaded to other locations for re-shooting.
At the same time, there is a transition – requiring devices that can carry more richly stored content with you. The DVD is transitioning from standard definition movies (5.7GB) to high definition movies (25GB).
More and more content can be carried around, the first is a flash memory-based music player, which can only play 60 minutes of music, and now gradually transition to a hard disk drive-based playback with 80GB of storage (which can hold 20,000 songs) Device.
This shift then occurs on portable media players (PMPs) that can play video at any time, and the next-generation PMP will be able to play high-definition movies. Finally, the new business model (that is, the "local cache" of new video releases in PVR-like devices that can be downloaded to portable players) will make high-speed connectivity a prerequisite for large file transfers.
What areas does SuperSpeed ​​USB apply to? All mass storage devices that need to perform "fast data instant synchronization" with your computer. The goal of instant synchronization is no more than 90s, beyond which many end users will feel unbearable.
Many of these types of portable devices use flash memory. Capacity will continue to grow, which is caused by consumer demand, sharp increases in flash capacity, and reduced costs.
Therefore, flash-based peripherals will benefit and ultimately require a much higher SuperSpeed ​​USB data transfer rate. Among them, including the most common USB peripherals - the ubiquitous flash drive! Table 1 summarizes the user experience from USB full speed to high speed to ultra high speed USB.
Multimedia applications that require a large number of files or large files to move quickly between personal computers will benefit from SuperSpeed ​​USB. It provides a satisfying bandwidth for users who need to synchronize multimedia data between computers and portable consumer products.
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