SAN FRANCISCO Just as systems and chip companies prepare to cut the umbilical cord that ties USB devices to the PC, a high-speed version of the connectivity standard is taking shape in systems that could appear before year's end.
Running at 480 Mbits/second, this USB offshoot promises to speed the flow of data for peripherals and handheld systems with video or mass-storage capabilities. But its advent has sparked a debate between two rival camps trying to field a common interface for the silicon at the heart of these systems.
Several companies say the 480-Mbit/s "high-speed" version of USB 2.0 is already making its way into embedded-system designs. If so, the rollout will coincide with that of the 12-Mbit/s "full-speed" version, which will serve the bulk of USB applications. "Most solutions are full-speed, but people know high-speed is out there, and we have some customers asking about it," said Brian Booker, USB product manager at Cypress Semiconductor Corp.
In most cases, high-speed USB is being coupled with the "On The Go" specification, a subset of USB 2.O that will allow, for example, a personal digital assistant to connect directly to a USB-enabled printer without the help of a PC. A number of vendors have hit the market with USB On-The-Go silicon: ARC, Cypress, Oki, Philips and TransDimension, among others.
At the same time, the USB Implementers Forum Inc., a group of companies that develops the USB specs, is gearing up to finish its certification-testing process for On-The-Go devices by this summer.
Plans by cell phone chip set makers Motorola, Qualcomm and Texas Instruments have also fueled interest in USB On-The-Go. "The market for OTG is zero today but there's going to be some dramatic growth in the next 12 months," said David Murray, vice president of marketing at TransDimension (Irvine, Calif.). "Within a year or two it's going to be a checklist item."
Microsoft Corp., for one, is using USB On-The-Go for its Media2Go platform, an early prototype of which was on display here at the Embedded Systems Conference last week. The first version works as a PC client, but a second reference design slated to come out in 2004 will have USB On-The-Go capability, most likely the high-speed version to better handle video bandwidth, said Bill Wittress, product manager for the embedded and appliance platforms group at Microsoft.
Wittress said Microsoft will add a component to its Windows CE.Net operating system to support USB On-The-Go, either by adding it to the base OS or by delivering a custom version for the PDA platform. It should be completed in the next 18 months, he said.
Officials at intellectual-property (IP) vendor ARC International said they expect some high-speed On-The-Go products will hit store shelves by the end of 2003. Eight of 15 customers designing On-The-Go devices using ARC's controller IP are designing the high-speed version, said Chris Belanger, product-marketing manager at ARC.
A brewing battle over chip interfaces, however, could pose a barrier to the standardization of the 480-Mbit/s version of USB. The dispute revolves around efforts to link USB controller chips to a separate transceiver that sends and receives the data between applications. The two approaches being proposed have a common goal: to limit the number of pins needed to connect transceiver and controller.
Philips Semiconductors has proposed a bus "wrapper" that would essentially packetize the data streaming through the transceiver in a fast, serialized manner to keep the number of pins to a minimum. Several chip vendors and IP core suppliers have voiced support for the nascent standard, known simply as the Low Pin Count (LPC) interface.
More recently, Cypress Semiconductor has proposed a similar but more ambitious effort called Super High PHY. This interface also aims to limit the pin count, but seeks to work with other I/O protocols beyond USB, said people familiar with the specification. "The line of demarcation between what is the PHY [physical-layer device] and what is a controller is being radically redrawn with Super High PHY," said Belanger of ARC.
The debate might never have arisen were it not for an unfortunate consequence of process technology advancement. Normally chip vendors would try to integrate the host and transceiver on the same piece of silicon. But as finer process technologies become more mainstream, chip makers say they are less confident they will be able to sustain the 5-volt tolerance needed for the analog portion of a USB transceiver. The worries start at 0.13 micron, which is now being qualified for volume production. Most observers agree that 90-nanometer process technologies won't support 5 V at all.
Indeed, most observers interviewed said a separate transceiver will be a must. Above 0.13 micron, however, many chip vendors should be able to integrate the controller and transceiver through an on-chip interface called UTMI-plus, which is expected to be finalized in coming weeks. An extension of the UTMI interface developed by Intel Corp. for USB chips, UTMI-plus adds signaling so that USB On-The-Go devices can act as either a host or a peripheral.