The Next Step, Hi-Speed USB 2.0

Introduction, Continued

The companies that created the USB specification founded the non-profit organization entitled "USB Implementers Forum, Inc." The USB-IF was formed to provide a support organization and forum for the advancement and adoption of Universal Serial Bus technology. The Forum facilitates the development of high-quality, compatible USB peripherals (devices), and promotes the benefits of USB and the quality of products that have passed compliance testing.

Just like any other standard (such as IEEE 1394, DTS, WiFi, Dolby, USB, or DVD), there is an official logo for USB 1.0, as well as for the new USB 2.0 standard. Manufacturers put these logos on their devices and packaging to show compliance with the established reference standard. These logos give you some assurance of compatibility and testing. The Hi-Speed USB 2.0 logo is used to show that the device will function correctly with other devices that carry the Hi-Speed USB 2.0 logo. If a device doesn't have the logo but claims Hi-Speed support, there is no guarantee that it will function with a certified USB 2.0 device. For best compatibility, it is reccomended that you use only certified USB devices.

For a company's device to bear the official Hi-Speed USB 2.0 logo, the company must be a paying ($2500/yr) member of USB-IF and the device must pass the compliance test procedures defined in the USB-IF Full and Low Speed Test Procedure. The purpose of these test procedures is to evaluate the full and low speed operation of USB silicon that has been incorporated in ready-to-ship products. The documented procedures address the compliance of the three groups listed by applying each group's respective test procedures:

• Add-in cards, motherboards, and systems
• Power Provider (Droop/Drop) testingDownstream Signal QualityInteroperability
• Full speed and low speed hubs (no high speed support)
• Power Provider (Droop/Drop) testingDown Signal QualityUpstream Signal QualityDevice Framework TestingInteroperabilityAverage Current Consumption
• Full speed or low speed peripherals
• Upstream Signal QualityDevice Framework TestingInteroperabilityAverage Current Consumption

With the higher speeds of USB 2.0 devices, designers must give attention to Device Packaging, Board Layout, Chassis Grounding, Trace Layout, EMI Remediation, and Data Signal Attenuation/ Jitter.

Hi-Speed USB delivers up to 40 times the bandwidth of a USB 1.1, with the new USB 2.0 delivering an incredible 480Mbps. Hi-Speed USB 2.0 is fully backward compatible with USB 1.1. In fact, you can intermix USB 2.0 and USB 1.1 devices. Of course, for the devices to work at USB 2.0 speed, they would have to be plugged into a USB 2.0 port. Similarly, if you plug a USB 1.1 device into USB 1.1 port, it will operate at USB 1.1 speeds. To achieve the incredible speed that USB 2.0 has to offer, you must have a USB 2.0 capible device plugged into a USB 2.0.