Universal Serial Bus

Current trends and new developments in personal computers provide a preview of new capabilities that we can expect to see implemented in PC-based controls in the near future. Another of these new PC developments destined to have a major impact on all PC based control systems is Universal Serial Bus (USB).

Columns From: 8/1/1999 Modern Machine Shop,

Current trends and new developments in personal computers provide a preview of new capabilities that we can expect to see implemented in PC-based controls in the near future. Another of these new PC developments destined to have a major impact on all PC based control systems is Universal Serial Bus (USB). USB interfaces have started appearing on many new computers this year as well as on a wide variety of peripheral devices.

USB is a new 4-wire bus that provides a better way to plug peripherals into a computer. "Universal" is the key word in this new interface's name since it replaces many different kinds of serial and parallel port connectors with one standardized plug and port combination. There are a wide variety of computer peripherals with USB connections. These include devices such as keyboards, digital cameras, floppy drives, tape drives, CD-ROM drives, mice, scanners, printers, telephones, modems and more. As of early 1999 there are more that 100 USB compatible peripheral products on the market with hundreds more expected to arrive throughout the year.

It is easy to understand why USB is so desirable in PCs when you look at its user benefits:

Easier Setup: USB eliminates the need to pry open your computer case, adjust system settings, install interface cards, fiddle with dip switches, figure out a port assignment, or assign a very touchy IRQ. A USB compatible peripheral is instantly recognized as soon as it is plugged into the computer and immediately put to work.

Easier Expansion: Theoretically, a USB compatible PC can run 127 peripherals daisy-chained from a single USB port. Devices can be added or removed without turning off the computer and rebooting. This is referred to as "hot swapping."

Better Performance: USB makes things work faster than when connected to a serial or parallel port. Data is transferred at 12 Mbps, which provides significant improvement for devices like scanners and digital cameras.

Lower Cost: USB devices use less electricity since they do not require separate power supplies for each unit. The power is transmitted through the connector. Also, since USB devices do not need additional interface cards, the cost to add a new peripheral is further reduced.

Noting all of the benefits that USB brings to PCs raises an interesting question. Will USB replace both the serial and parallel ports that have for so long been the standard on PCs? PC industry analysts speculate that USB will not replace traditional PC ports overnight, but it is expected to rapidly become the preferred method of connecting low and medium bandwidth peripherals. One research firm, Dataquest, forecasts that by the year 2001 all new PCs will be USB compatible.

Even though USB operates at 12 Mbps, it is not adequate for all computer peripherals. Devices that require ultra-high throughput such as camcorders or heavy-duty storage devices need a considerably faster data transfer rate. This need is being filled by another new interface, "FireWire" (see CIM Perspectives March, 1999). FireWire does everything that USB does but at the data transfer rates of 100 or 400 Mbps.

Combine the user benefits of USB with its major supporters such as Compaq, IBM, Intel, and Microsoft, and it becomes understandable why there has been such a rapid transition to this new interface standard. With USB designated to become the new PC standard for interface ports, it is significant to note that USB will not increase the prices of PCs. In fact, it most likely will reduce the price of peripherals due to the absence of additional interface cards and the elimination of multiple power supplies.

When USB ports begin appearing in PC-based control systems will of course depend largely on the control builder and its basic design concepts. For controls where the OEM or end user purchases only the control software from a control vendor and add off-the-shelf PCs hardware, USB is most likely available on the PCs being bought today. For controls where PCs are integrated into the control package by the control builder, the delay on average is approximately two years for new PC designs to filter down to production versions of controls. Whether it is sooner or later, USB promises to add another link in the movement to truly open architecture.

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